syntax_data: {"ast_node_type":"variable","tokens":[{"end":56,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let (lhs_success_block, failure_block) =
context_before:                 let local_scope = this.local_scope();
context_after:                     this.in_if_then_scope(local_scope, expr_span, |this| {