syntax_data: {"ast_node_type":"other","tokens":[{"end":51,"kind":"keyword","start":0,"text":"this.source_info(arm.span),"}]}
source_snippet:                         this.source_info(arm.span),
context_before:                         None, // Use `self.local_scope()` as the temp scope
context_after:                         DeclareLetBindings::No, // For guards, `let` bindings are declared separately