There's nothing wrong with this, so I approved, but this demonstrates once again why I dislike the GenericType more and more: to be practically useful, it needs to spread throughout the codebase, even though the primary usecase (generating signatures) is something very few users actually care about. They would get that for free if they used GenericType, but constructing it is actually fairly hard, so I predict very few people will actually care, since it's totally optional. Oh well.

Actually one thing: we should probably validate that the erasure of the given generic type is equal to the ClassDesc of the field descriptor / method return type / etc.