error[E0277]: the trait bound `fn() -> bool {example}: Foo` is not satisfied
  --> $DIR/fn-trait-cast-diagnostic.rs:21:15
   |
LL |     do_on_foo(example);
   |     --------- ^^^^^^^ the trait `Foo` is not implemented for fn item `fn() -> bool {example}`
   |     |
   |     required by a bound introduced by this call
   |
note: required by a bound in `do_on_foo`
  --> $DIR/fn-trait-cast-diagnostic.rs:17:22
   |
LL | fn do_on_foo(v: impl Foo) {}
   |                      ^^^ required by this bound in `do_on_foo`
help: use parentheses to call this function
   |
LL |     do_on_foo(example());
   |                      ++
help: the trait `Foo` is implemented for fn pointer `fn() -> bool`, try casting using `as`
   |
LL |     do_on_foo(example as fn() -> bool);
   |                       +++++++++++++++

error[E0277]: the trait bound `fn() -> bool {example}: NoOtherFoo` is not satisfied
  --> $DIR/fn-trait-cast-diagnostic.rs:24:22
   |
LL |     do_on_single_foo(example);
   |     ---------------- ^^^^^^^ the trait `NoOtherFoo` is not implemented for fn item `fn() -> bool {example}`
   |     |
   |     required by a bound introduced by this call
   |
note: required by a bound in `do_on_single_foo`
  --> $DIR/fn-trait-cast-diagnostic.rs:18:29
   |
LL | fn do_on_single_foo(v: impl NoOtherFoo) {}
   |                             ^^^^^^^^^^ required by this bound in `do_on_single_foo`
help: the trait `NoOtherFoo` is implemented for fn pointer `fn() -> bool`, try casting using `as`
   |
LL |     do_on_single_foo(example as fn() -> bool);
   |                              +++++++++++++++

error: aborting due to 2 previous errors

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