error[E0277]: the size for values of type `(dyn std::ops::FnOnce() + 'static)` cannot be known at compilation time --> $DIR/feature-gate-unsized_locals.rs:11:6 | LL | fn f(f: FnOnce()) {} | ^ doesn't have a size known at compile-time | = help: the trait `std::marker::Sized` is not implemented for `(dyn std::ops::FnOnce() + 'static)` = note: to learn more, visit = note: all local variables must have a statically known size = help: unsized locals are gated as an unstable feature error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.