Pre-RFC: Generic parameters in derive

[cuviper]

FWIW, this is pretty close to the syntax I suggested here:

Idea: explicit type parameters for derivation

Motivation Idea We could add explicit type parameters in the derive attribute, indicating which ones ought to be used as constraints in the expanded derivation. These would be equivalent: // The derivations require `T: Copy` and `T: Clone` respectively #[derive(Copy, Clone)] struct Y<T>(&'static fn(T)); // explicitly constrain `T` the same way #[derive<T>(Copy, Clone)] struct Z<T>(&'static fn(T)); But with an explicit list, you could choose partial constraints, or even no constraints at all…

Although apart from syntax, you've also chosen a bit different meaning in how to apply those generics. I'm not sure if that would be more or less palatable to the language team.