tests/ui/feature-gates/feature-gate-unsized_locals.stderr

   1 error[E0277]: the size for values of type `(dyn FnOnce() + 'static)` cannot be known at compilation time
   2   --> $DIR/feature-gate-unsized_locals.rs:1:6
   3    |
   4 LL | fn f(f: dyn FnOnce()) {}
   5    |      ^ doesn't have a size known at compile-time
   6    |
   7    = help: the trait `Sized` is not implemented for `(dyn FnOnce() + 'static)`
   8    = help: unsized fn params are gated as an unstable feature
   9 help: you can use `impl Trait` as the argument type
  10    |
  11 LL | fn f(f: impl FnOnce()) {}
  12    |         ~~~~
  13 help: function arguments must have a statically known size, borrowed types always have a known size
  14    |
  15 LL | fn f(f: &dyn FnOnce()) {}
  16    |         +
  17
  18 error: aborting due to previous error
  19
  20 For more information about this error, try `rustc --explain E0277`.