syntax_data: {"ast_node_type":"other","tokens":[{"end":68,"kind":"keyword","start":0,"text":"this.with_let_source(LetSource::IfLetGuard,"}]}
source_snippet:                 this.with_let_source(LetSource::IfLetGuard, |this| {
context_before:             if let Some(expr) = arm.guard {
context_after:                     this.visit_expr(&this.thir[expr])