[ra-ap-hir] hir::VariantDef can be impl HasSource

[snprajwal]

Similar to how all variants of hir::Adt are HasSource, allowing the enum itself to be impl HasSource, the same can be done for hir::VariantDef. This would require introducing a new ast::VariantDef enum in ra-ap-syntax to be able to map the source between the two.

[ChayimFriedman2]

Do you actually need this for your project, or do you just want it to be included for completeness?

[snprajwal]

Purely for completeness. It's quite trivial to work around this with a match block - it just adds consistency to the API since every other sum type I'm aware of implements traits that all variants implement. If acceptable, I'd be happy to put a PR up!