{"ast_node_type":"other","tokens":[{"end":64,"kind":"keyword","start":0,"text":".unwrap_or_else(||"}]}
                .unwrap_or_else(|| self.next_ty_var(expr.span));
                .and_then(|uty| self.try_structurally_resolve_type(expr.span, uty).builtin_index())
            let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);