error[E0646]: `main` function is not allowed to have a `where` clause
  --> $DIR/issue-50714.rs:3:11
   |
LL | fn main() where fn(&()): Eq {}
   |           ^^^^^^^^^^^^^^^^^ `main` cannot have a `where` clause

error: aborting due to previous error

For more information about this error, try `rustc --explain E0646`.