No Mirror.SumOf available for case with secondary parameter list

[bishabosha]

Minimized code

enum Foo:
  case Branch()(i: Int)

def m = summon[deriving.Mirror.SumOf[Foo]] 

Output

1 |def m = summon[deriving.Mirror.SumOf[Foo]]
  |                                          ^
  |no implicit argument of type deriving.Mirror.SumOf[Foo] was found for parameter x of method summon in object DottyPredef

Expectation

It seems limiting that Mirror is only defined for classes with state purely represented by their extractors. This also means there is no generic API for enum companions as summon[Mirror.SumOf[MyEnum]].ordinal(foo) is not always defined

[odersky]

We discussed this and decided to leave things as they are