syntax_data: {"ast_node_type":"variable","tokens":[{"end":45,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let old_let_source = self.let_source;
context_before:     fn with_let_source(&mut self, let_source: LetSource, f: impl FnOnce(&mut Self)) {
context_after:         self.let_source = let_source;