error[E0741]: `C` must implement `ConstParamTy` to be used as the type of a const generic parameter
  --> $DIR/forbid-non-structural_match-types.rs:13:19
   |
LL | struct D<const X: C>;
   |                   ^
   |
help: add `#[derive(ConstParamTy, PartialEq, Eq)]` to the struct
   |
LL + #[derive(ConstParamTy, PartialEq, Eq)]
LL | struct C;
   |

error: aborting due to 1 previous error

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