syntax_data: {"ast_node_type":"variable","tokens":[{"end":64,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                     let expanded_ty = self.fold_ty(concrete_ty);
context_before:                     let concrete_ty = generic_ty.instantiate(self.tcx, args);
context_after:                     self.expanded_cache.insert((def_id, args), expanded_ty);