| error[E0658]: parenthetical notation is only stable when used with `Fn`-family traits | |
| --> $DIR/unboxed-closure-feature-gate.rs:13:20 | |
| | | |
| LL | let x: Box<dyn Foo(isize)>; | |
| | ^^^^^^^^^^ | |
| | | |
| = note: for more information, see https://github.com/rust-lang/rust/issues/29625 | |
| = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0658`. |