syntax_data: {"ast_node_type":"variable","tokens":[{"end":53,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let match_scope = self.local_scope();
context_before:                 let arm_scope = (arm.scope, arm_source_info);
context_after:                 self.in_scope(arm_scope, arm.lint_level, |this| {