error[E0631]: type mismatch in closure arguments
  --> $DIR/issue-41366.rs:10:5
   |
LL |     (&|_| ()) as &dyn for<'x> Fn(<u32 as T<'x>>::V);
   |     ^^------^
   |     | |
   |     | found signature of `fn(u16) -> _`
   |     expected signature of `fn(<u32 as T<'x>>::V) -> _`
   |
   = note: required for the cast to the object type `dyn for<'x> Fn(<u32 as T<'x>>::V)`

error[E0277]: the size for values of type `<u32 as T<'_>>::V` cannot be known at compilation time
  --> $DIR/issue-41366.rs:10:8
   |
LL |     (&|_| ()) as &dyn for<'x> Fn(<u32 as T<'x>>::V);
   |        ^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `<u32 as T<'_>>::V`
   = help: unsized fn params are gated as an unstable feature
help: consider further restricting the associated type
   |
LL | fn main() where <u32 as T<'_>>::V: Sized {
   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: function arguments must have a statically known size, borrowed types always have a known size
   |
LL |     (&|&_| ()) as &dyn for<'x> Fn(<u32 as T<'x>>::V);
   |        ^

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0277, E0631.
For more information about an error, try `rustc --explain E0277`.