syntax_data: {"ast_node_type":"variable","tokens":[{"end":56,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let mirrored = self.mirror_expr(source);
context_before:                 // FIXME(unsafe_binders): Take into account the ascribed type, too.
context_after:                 if source.is_syntactic_place_expr() {