error[E0658]: the precise format of `Fn`-family traits' type parameters is subject to change. Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead (see issue #29625) --> $DIR/unboxed-closure-sugar-not-used-on-fn.rs:14:13 | LL | fn bar1(x: &Fn<(), Output=()>) { | ^^^^^^^^^^^^^^^^^ | = help: add #![feature(unboxed_closures)] to the crate attributes to enable error[E0658]: the precise format of `Fn`-family traits' type parameters is subject to change. Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead (see issue #29625) --> $DIR/unboxed-closure-sugar-not-used-on-fn.rs:18:28 | LL | fn bar2(x: &T) where T: Fn<()> { | ^^^^^^ | = help: add #![feature(unboxed_closures)] to the crate attributes to enable error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0658`.