error[E0308]: cannot coerce functions which must be inlined to function pointers
  --> $DIR/cast.rs:10:33
   |
LL |     let _: fn(isize) -> usize = callee;
   |            ------------------   ^^^^^^ cannot coerce functions which must be inlined to function pointers
   |            |
   |            expected due to this
   |
   = note: expected fn pointer `fn(_) -> _`
                 found fn item `fn(_) -> _ {callee}`
   = note: fn items are distinct from fn pointers
help: consider casting to a fn pointer
   |
LL |     let _: fn(isize) -> usize = callee as fn(isize) -> usize;
   |                                        +++++++++++++++++++++

error[E0605]: non-primitive cast: `fn(isize) -> usize {callee}` as `fn(isize) -> usize`
  --> $DIR/cast.rs:15:13
   |
LL |     let _ = callee as fn(isize) -> usize;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ invalid cast

error[E0308]: cannot coerce functions which must be inlined to function pointers
  --> $DIR/cast.rs:21:9
   |
LL |         callee,
   |         ^^^^^^ cannot coerce functions which must be inlined to function pointers
   |
   = note: expected fn pointer `fn(_) -> _`
                 found fn item `fn(_) -> _ {callee}`
   = note: fn items are distinct from fn pointers
help: consider casting to a fn pointer
   |
LL |         callee as fn(isize) -> usize,
   |                +++++++++++++++++++++

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0308, E0605.
For more information about an error, try `rustc --explain E0308`.