[STATEMENT]
lemma get_ancestors_si_obtains_children_or_shadow_root:
  assumes "heap_is_wellformed h" and "known_ptrs h" and "type_wf h"
    and "h \<turnstile> get_ancestors_si ptr \<rightarrow>\<^sub>r ancestors"
    and "ancestor \<noteq> ptr"
    and "ancestor \<in> set ancestors"
  shows "((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow>
ancestor_child \<in> set children \<longrightarrow> cast ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
      \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast ancestor_element \<longrightarrow>
h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow>
thesis)"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
proof (insert assms(4) assms(5) assms(6), induct ptr arbitrary: ancestors
    rule: heap_wellformed_induct_rev_si[OF assms(1)])
[PROOF STATE]
proof (state)
goal (1 subgoal):
 1. \<And>child ancestors. \<lbrakk>\<And>parent child_node ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>host shadow_root ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_doc disc_node ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
case (1 child)
[PROOF STATE]
proof (state)
this:
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?child_node; h \<turnstile> get_parent ?child_node \<rightarrow>\<^sub>r Some ?parent; h \<turnstile> get_ancestors_si ?parent \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> ?parent; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?shadow_root; h \<turnstile> get_host ?shadow_root \<rightarrow>\<^sub>r ?host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_node; h \<turnstile> get_disconnected_document ?disc_node \<rightarrow>\<^sub>r ?disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
ancestor \<noteq> child
ancestor \<in> set ancestors

goal (1 subgoal):
 1. \<And>child ancestors. \<lbrakk>\<And>parent child_node ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>host shadow_root ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_doc disc_node ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?child_node; h \<turnstile> get_parent ?child_node \<rightarrow>\<^sub>r Some ?parent; h \<turnstile> get_ancestors_si ?parent \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> ?parent; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?shadow_root; h \<turnstile> get_host ?shadow_root \<rightarrow>\<^sub>r ?host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_node; h \<turnstile> get_disconnected_document ?disc_node \<rightarrow>\<^sub>r ?disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
ancestor \<noteq> child
ancestor \<in> set ancestors
[PROOF STEP]
show ?case
[PROOF STATE]
proof (prove)
using this:
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?child_node; h \<turnstile> get_parent ?child_node \<rightarrow>\<^sub>r Some ?parent; h \<turnstile> get_ancestors_si ?parent \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> ?parent; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?shadow_root; h \<turnstile> get_host ?shadow_root \<rightarrow>\<^sub>r ?host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_node; h \<turnstile> get_disconnected_document ?disc_node \<rightarrow>\<^sub>r ?disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
ancestor \<noteq> child
ancestor \<in> set ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
proof (cases "cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child")
[PROOF STATE]
proof (state)
goal (2 subgoals):
 1. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
case None
[PROOF STATE]
proof (state)
this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None

goal (2 subgoals):
 1. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None
[PROOF STEP]
obtain shadow_root where shadow_root: "child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root"
[PROOF STATE]
proof (prove)
using this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None

goal (1 subgoal):
 1. (\<And>shadow_root. child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<Longrightarrow> thesis) \<Longrightarrow> thesis
[PROOF STEP]
using 1(4) 1(5) 1(6)
[PROOF STATE]
proof (prove)
using this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
ancestor \<noteq> child
ancestor \<in> set ancestors

goal (1 subgoal):
 1. (\<And>shadow_root. child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<Longrightarrow> thesis) \<Longrightarrow> thesis
[PROOF STEP]
by(auto simp add: get_ancestors_si_def[of child] elim!: bind_returns_result_E2
          split: option.splits)
[PROOF STATE]
proof (state)
this:
child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root

goal (2 subgoals):
 1. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root
[PROOF STEP]
obtain host where host: "h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host"
[PROOF STATE]
proof (prove)
using this:
child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root

goal (1 subgoal):
 1. (\<And>host. h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host \<Longrightarrow> thesis) \<Longrightarrow> thesis
[PROOF STEP]
by (metis "1.prems"(1) assms(1) assms(2) assms(3) document_ptr_kinds_commutes
          get_ancestors_si_ptrs_in_heap is_OK_returns_result_E local.get_ancestors_si_ptr local.get_host_ok
          shadow_root_ptr_kinds_commutes)
[PROOF STATE]
proof (state)
this:
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host

goal (2 subgoals):
 1. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host
[PROOF STEP]
obtain host_ancestors where host_ancestors: "h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors"
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host

goal (1 subgoal):
 1. (\<And>host_ancestors. h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors \<Longrightarrow> thesis) \<Longrightarrow> thesis
[PROOF STEP]
by (metis "1.prems"(1) assms(1) assms(2) assms(3) get_ancestors_si_also_host get_ancestors_si_ok
          get_ancestors_si_ptrs_in_heap is_OK_returns_result_E local.get_ancestors_si_ptr shadow_root)
[PROOF STATE]
proof (state)
this:
h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors

goal (2 subgoals):
 1. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors
[PROOF STEP]
have "ancestors = cast shadow_root # host_ancestors"
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors

goal (1 subgoal):
 1. ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors
[PROOF STEP]
using 1(4) 1(5) 1(3) None shadow_root host
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
ancestor \<noteq> child
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_node; h \<turnstile> get_disconnected_document ?disc_node \<rightarrow>\<^sub>r ?disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None
child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host

goal (1 subgoal):
 1. ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors
[PROOF STEP]
by(auto simp add: get_ancestors_si_def[of child, simplified shadow_root]
          elim!: bind_returns_result_E2 dest!: returns_result_eq[OF host] split: option.splits)
[PROOF STATE]
proof (state)
this:
ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors

goal (2 subgoals):
 1. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = None\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors
[PROOF STEP]
show ?thesis
[PROOF STATE]
proof (prove)
using this:
ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
proof (cases "ancestor = cast host")
[PROOF STATE]
proof (state)
goal (2 subgoals):
 1. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
case True
[PROOF STATE]
proof (state)
this:
ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host

goal (2 subgoals):
 1. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host
[PROOF STEP]
show ?thesis
[PROOF STATE]
proof (prove)
using this:
ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
using "1.prems"(1) host local.get_ancestors_si_ptr local.shadow_root_host_dual shadow_root
[PROOF STATE]
proof (prove)
using this:
ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host
?h \<turnstile> get_ancestors_si ?ptr \<rightarrow>\<^sub>r ?ancestors \<Longrightarrow> ?ptr \<in> set ?ancestors
?h \<turnstile> get_host ?shadow_root_ptr \<rightarrow>\<^sub>r ?host \<Longrightarrow> ?h \<turnstile> get_shadow_root ?host \<rightarrow>\<^sub>r Some ?shadow_root_ptr
child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
by blast
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
next
[PROOF STATE]
proof (state)
goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
case False
[PROOF STATE]
proof (state)
this:
ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
have "ancestor \<in> set ancestors"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. ancestor \<in> set ancestors
[PROOF STEP]
using host host_ancestors 1(3) get_ancestors_si_also_host assms(1) assms(2) assms(3)
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host
h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_node; h \<turnstile> get_disconnected_document ?disc_node \<rightarrow>\<^sub>r ?disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>heap_is_wellformed ?h; ?h \<turnstile> get_ancestors_si ?some_ptr \<rightarrow>\<^sub>r ?ancestors; cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?shadow_root \<in> set ?ancestors; ?h \<turnstile> get_host ?shadow_root \<rightarrow>\<^sub>r ?host; type_wf ?h; known_ptrs ?h\<rbrakk> \<Longrightarrow> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host \<in> set ?ancestors
heap_is_wellformed h
known_ptrs h
type_wf h

goal (1 subgoal):
 1. ancestor \<in> set ancestors
[PROOF STEP]
using "1.prems"(3)
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host
h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_node; h \<turnstile> get_disconnected_document ?disc_node \<rightarrow>\<^sub>r ?disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
\<lbrakk>heap_is_wellformed ?h; ?h \<turnstile> get_ancestors_si ?some_ptr \<rightarrow>\<^sub>r ?ancestors; cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?shadow_root \<in> set ?ancestors; ?h \<turnstile> get_host ?shadow_root \<rightarrow>\<^sub>r ?host; type_wf ?h; known_ptrs ?h\<rbrakk> \<Longrightarrow> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host \<in> set ?ancestors
heap_is_wellformed h
known_ptrs h
type_wf h
ancestor \<in> set ancestors

goal (1 subgoal):
 1. ancestor \<in> set ancestors
[PROOF STEP]
by blast
[PROOF STATE]
proof (state)
this:
ancestor \<in> set ancestors

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
ancestor \<in> set ancestors
[PROOF STEP]
have "((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow>
ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow>
thesis) \<or>
          ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow>
h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow>
cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)"
[PROOF STATE]
proof (prove)
using this:
ancestor \<in> set ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
using "1.hyps"(2) "1.prems"(2) False \<open>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors\<close>
          host host_ancestors shadow_root
[PROOF STATE]
proof (prove)
using this:
ancestor \<in> set ancestors
\<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?shadow_root; h \<turnstile> get_host ?shadow_root \<rightarrow>\<^sub>r ?host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?host; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
ancestor \<noteq> child
ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host
ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors
h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host
h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r host_ancestors
child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
by auto
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
show ?thesis
[PROOF STATE]
proof (prove)
using this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
using \<open>ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors\<close>
[PROOF STATE]
proof (prove)
using this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set host_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
ancestors = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root # host_ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
by auto
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal:
No subgoals!
[PROOF STEP]
qed
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal (1 subgoal):
 1. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
next
[PROOF STATE]
proof (state)
goal (1 subgoal):
 1. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
case (Some child_node)
[PROOF STATE]
proof (state)
this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some child_node

goal (1 subgoal):
 1. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some child_node
[PROOF STEP]
obtain parent where parent: "h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent"
[PROOF STATE]
proof (prove)
using this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some child_node

goal (1 subgoal):
 1. (\<And>parent. h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent \<Longrightarrow> thesis) \<Longrightarrow> thesis
[PROOF STEP]
using 1(4) 1(5) 1(6)
[PROOF STATE]
proof (prove)
using this:
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some child_node
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
ancestor \<noteq> child
ancestor \<in> set ancestors

goal (1 subgoal):
 1. (\<And>parent. h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent \<Longrightarrow> thesis) \<Longrightarrow> thesis
[PROOF STEP]
by(auto simp add: get_ancestors_si_def[of child] elim!: bind_returns_result_E2
          split: option.splits)
[PROOF STATE]
proof (state)
this:
h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent

goal (1 subgoal):
 1. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent
[PROOF STEP]
obtain parent_ancestors where parent_ancestors: "h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r parent_ancestors"
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent

goal (1 subgoal):
 1. (\<And>parent_ancestors. h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r parent_ancestors \<Longrightarrow> thesis) \<Longrightarrow> thesis
[PROOF STEP]
by (meson assms(1) assms(2) assms(3) get_ancestors_si_ok is_OK_returns_result_E
          local.get_parent_parent_in_heap)
[PROOF STATE]
proof (state)
this:
h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r parent_ancestors

goal (1 subgoal):
 1. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r parent_ancestors
[PROOF STEP]
have "ancestors = cast child_node # parent_ancestors"
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r parent_ancestors

goal (1 subgoal):
 1. ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors
[PROOF STEP]
using 1(4) 1(5) 1(3) Some
[PROOF STATE]
proof (prove)
using this:
h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r parent_ancestors
h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors
ancestor \<noteq> child
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_node; h \<turnstile> get_disconnected_document ?disc_node \<rightarrow>\<^sub>r ?disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc) \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?disc_doc; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some child_node

goal (1 subgoal):
 1. ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors
[PROOF STEP]
by(auto simp add: get_ancestors_si_def[of child, simplified Some]
          elim!: bind_returns_result_E2 dest!: returns_result_eq[OF parent] split: option.splits)
[PROOF STATE]
proof (state)
this:
ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors

goal (1 subgoal):
 1. \<And>a. \<lbrakk>\<And>child_node parent ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node; h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent; h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> parent; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>shadow_root host ancestors. \<lbrakk>child = cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root; h \<turnstile> get_host shadow_root \<rightarrow>\<^sub>r host; h \<turnstile> get_ancestors_si (cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r host; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); \<And>disc_node disc_doc ancestors. \<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_node; h \<turnstile> get_disconnected_document disc_node \<rightarrow>\<^sub>r disc_doc; h \<turnstile> get_ancestors_si (cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc) \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> cast\<^sub>d\<^sub>o\<^sub>c\<^sub>u\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r disc_doc; ancestor \<in> set ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis); h \<turnstile> get_ancestors_si child \<rightarrow>\<^sub>r ancestors; ancestor \<noteq> child; ancestor \<in> set ancestors; cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some a\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors
[PROOF STEP]
show ?thesis
[PROOF STATE]
proof (prove)
using this:
ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
proof (cases "ancestor = parent")
[PROOF STATE]
proof (state)
goal (2 subgoals):
 1. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor = parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor \<noteq> parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
case True
[PROOF STATE]
proof (state)
this:
ancestor = parent

goal (2 subgoals):
 1. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor = parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
 2. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor \<noteq> parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
ancestor = parent
[PROOF STEP]
show ?thesis
[PROOF STATE]
proof (prove)
using this:
ancestor = parent

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
by (metis (no_types, lifting) "1.prems"(1) Some local.get_ancestors_si_ptr
            local.get_parent_child_dual node_ptr_casts_commute parent)
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor \<noteq> parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
next
[PROOF STATE]
proof (state)
goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor \<noteq> parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
case False
[PROOF STATE]
proof (state)
this:
ancestor \<noteq> parent

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor \<noteq> parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
have "ancestor \<in> set ancestors"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. ancestor \<in> set ancestors
[PROOF STEP]
by (simp add: "1.prems"(3))
[PROOF STATE]
proof (state)
this:
ancestor \<in> set ancestors

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor \<noteq> parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
ancestor \<in> set ancestors
[PROOF STEP]
have "((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow>
ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow>
thesis) \<or>
         ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow>
h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow>
cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)"
[PROOF STATE]
proof (prove)
using this:
ancestor \<in> set ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
using "1.hyps"(1) "1.prems"(2) False Some \<open>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors\<close>
          parent parent_ancestors
[PROOF STATE]
proof (prove)
using this:
ancestor \<in> set ancestors
\<lbrakk>child = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ?child_node; h \<turnstile> get_parent ?child_node \<rightarrow>\<^sub>r Some ?parent; h \<turnstile> get_ancestors_si ?parent \<rightarrow>\<^sub>r ?ancestors; ancestor \<noteq> ?parent; ancestor \<in> set ?ancestors\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ?ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
ancestor \<noteq> child
ancestor \<noteq> parent
cast\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r child = Some child_node
ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors
h \<turnstile> get_parent child_node \<rightarrow>\<^sub>r Some parent
h \<turnstile> get_ancestors_si parent \<rightarrow>\<^sub>r parent_ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
by auto
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal (1 subgoal):
 1. \<lbrakk>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors; ancestor \<noteq> parent\<rbrakk> \<Longrightarrow> ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
then
[PROOF STATE]
proof (chain)
picking this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
show ?thesis
[PROOF STATE]
proof (prove)
using this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
using \<open>ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors\<close>
[PROOF STATE]
proof (prove)
using this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set parent_ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
ancestors = cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r child_node # parent_ancestors

goal (1 subgoal):
 1. ((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)
[PROOF STEP]
by auto
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal:
No subgoals!
[PROOF STEP]
qed
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal:
No subgoals!
[PROOF STEP]
qed
[PROOF STATE]
proof (state)
this:
((\<forall>children ancestor_child. h \<turnstile> get_child_nodes ancestor \<rightarrow>\<^sub>r children \<longrightarrow> ancestor_child \<in> set children \<longrightarrow> cast\<^sub>n\<^sub>o\<^sub>d\<^sub>e\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_child \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis) \<or> ((\<forall>ancestor_element shadow_root. ancestor = cast\<^sub>e\<^sub>l\<^sub>e\<^sub>m\<^sub>e\<^sub>n\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r ancestor_element \<longrightarrow> h \<turnstile> get_shadow_root ancestor_element \<rightarrow>\<^sub>r Some shadow_root \<longrightarrow> cast\<^sub>s\<^sub>h\<^sub>a\<^sub>d\<^sub>o\<^sub>w\<^sub>_\<^sub>r\<^sub>o\<^sub>o\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r\<^sub>2\<^sub>o\<^sub>b\<^sub>j\<^sub>e\<^sub>c\<^sub>t\<^sub>_\<^sub>p\<^sub>t\<^sub>r shadow_root \<in> set ancestors \<longrightarrow> thesis) \<longrightarrow> thesis)

goal:
No subgoals!
[PROOF STEP]
qed