error[E0369]: binary operation `==` cannot be applied to type `fn() {main::f}`
  --> $DIR/fn-compare-mismatch.rs:14:13
   |
LL |     let x = f == g;
   |             ^^^^^^
   |
   = note: an implementation of `std::cmp::PartialEq` might be missing for `fn() {main::f}`

error[E0308]: mismatched types
  --> $DIR/fn-compare-mismatch.rs:14:18
   |
LL |     let x = f == g;
   |                  ^ expected fn item, found a different fn item
   |
   = note: expected type `fn() {main::f}`
              found type `fn() {main::g}`

error: aborting due to 2 previous errors

Some errors occurred: E0308, E0369.
For more information about an error, try `rustc --explain E0308`.