error[E0277]: the trait bound `for<'r> fn(&'r i32): Foo` is not satisfied
  --> $DIR/issue-46989.rs:40:5
   |
LL | fn assert_foo<T: Foo>() {}
   | ----------------------- required by `assert_foo`
...
LL |     assert_foo::<fn(&i32)>();
   |     ^^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `for<'r> fn(&'r i32)`
   |
   = help: the following implementations were found:
             <fn(A) as Foo>

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.