syntax_data: {"ast_node_type":"variable","tokens":[{"end":100,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let layout: Tree<Def, !, !> = Tree::def(Def::NoSafetyInvariants).then(Tree::byte(0x00));
context_before:         fn seq_1() {
context_after:             assert_eq!(layout.prune(&|d| matches!(d, Def::HasSafetyInvariants)), Tree::byte(0x00));