Build break from #862

[heaths]

Describe the bug
Seems #862 broke the build by now always returning a result from <ModifierKeyCode as Display>::fmt. Also seems the #[cfg] attribute on the match itself isn't correct, as the individual match arms have conditions. Still, even without it still doesn't compile without some tweaks.

To Reproduce
Steps to reproduce the behavior:

1. Try to build.

Expected behavior
Build fails with:

    |
922 |     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    |        ---                                       ^^^^^^^^^^^ expected `Result<(), Error>`, found `()`
    |        |
    |        implicitly returns `()` as its body has no tail or `return` expression
    |
    = note:   expected enum `Result<(), std::fmt::Error>`
            found unit type `()`

OS

• Any

Terminal/Console

• Any