MirroredMonoType for curried type lambda has wrong kind

[bishabosha]

Compiler version

3.1.0

Minimized code

summon[deriving.Mirror.Product { type MirroredType = [X] =>> [Y] =>> (X, Y) }]

Output

1 |summon[deriving.Mirror.Product { type MirroredType = [X] =>> [Y] =>> (X, Y) }]
  |                                                                              ^
  |error overriding type MirroredMonoType in trait Mirror with bounds;
  |  type MirroredMonoType, which equals [Y] =>> (?, Y) has incompatible type

Expectation

MirroredMonoType should be collapsed to (?, ?), rather than [Y] =>> (?, Y)

[odersky]

Not clear why this should change. Maybe simply not support it?