Do not suggest `#[derive(Copy)]` when we wanted a `!Copy` type.
Do not say "`Copy` is not implemented for `T` but `Copy` is".
Do not talk about `Trait` having no implementations when `!Trait` was desired.
When a trait is not implemented for a type, but there *is* an `impl`
for another type or different trait params, we format the output to
use highlighting in the same way that E0308 does for types.
The logic accounts for 3 cases:
- When both the type and trait in the expected predicate and the candidate are different
- When only the types are different
- When only the trait generic params are different
For each case, we use slightly different formatting and wording.
