{"ast_node_type":"other","tokens":[{"end":61,"kind":"keyword","start":0,"text":"self.at(&self.misc(arg_span),"}]}
                self.at(&self.misc(arg_span), self.param_env)
            let subtyping_error = self.probe(|_| {
                    .sup(DefineOpaqueTypes::Yes, formal_input_ty, coerced_ty)