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 <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = 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`.