error[E0741]: `(fn(),)` can't be used as a const parameter type
  --> $DIR/issue-99641.rs:5:35
   |
LL |     pub struct Color<const WHITE: (fn(),)>;
   |                                   ^^^^^^^
   |
   = note: `fn()` must implement `ConstParamTy_`, but it does not

error[E0741]: `(fn(),)` can't be used as a const parameter type
  --> $DIR/issue-99641.rs:8:23
   |
LL |     impl<const WHITE: (fn(),)> Color<WHITE> {
   |                       ^^^^^^^
   |
   = note: `fn()` must implement `ConstParamTy_`, but it does not

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0741`.