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:                 debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
context_after:                 if source.is_syntactic_place_expr() {