It seems that in recent version TSTypeParameter.name has been extended to be string | K.IdentifierKind.
This results in a weird type cycle, where a name can be any identifier including TSTypeParameter again. Causing client code to deal with it somehow. It seems that babel-parser tests do not have any examples of generating anything apart from plain Identifier (or string) for TStypeParameter.name.
Should this be constrained a bit more?