syntax_data: {"ast_node_type":"variable","tokens":[{"end":53,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let (temp_lifetime, backwards_incompatible) =
context_before:         let expr_ty = self.typeck_results.expr_ty(expr);
context_after:             self.rvalue_scopes.temporary_scope(self.region_scope_tree, expr.hir_id.local_id);