Section 4.4.5. Group conversion of the spec is described as follows.
@ConvertGroup and @ConvertGroup.List can be used everywhere @Valid can be used (associations, method/constructor parameters and return value). If these annotations are used without @Valid, a ConstraintDeclarationException is raised.
But @ConvertGroup and @ConvertGroup.List target TYPE which @Valid does not.
So, remove TYPE from targets of @ConvertGroup.
That's a good find. I'll need to clarify though whether we can remove the wrong element type in terms of backwards compatibility (no one should ever have put @ConvertGroup to the type-level, but technically it would have been possible, so it may pose a (albeit quite theoretical) compatibility issue).
Thanks. I see why we cannot remove it.
Should I withdraw the current pull request?
May I leave this issue still open for adding a docmenttation comment?
As it turns out, TYPE_USE (which we've added to support group conversions on container element cascades) also allows the usage of the annotation on type definitions (see class-comment on ElementType), so the point about backwards compatibility is moot.