Erroneous Type Mismatch Error?

[sir-wabbit]

type Fst[t[_[_, _]]] = t[[a, b] => a]
type Snd[t[_[_, _]]] = t[[a, b] => b]
final case class Witness[t[_[_, _]], A <: Fst[t]](value: Snd[t])

The compiler prints out:

-- [E007] Type Mismatch Error: tests/alex/test.scala ---------------------------
70 |  final case class Witness[t[_[_, _]], A <: Fst[t]](value: Snd[t])
   |                                                                 ^
   |              found:    Snd[t](Witness.this.value)
   |              required: Snd[(? <: [_$7 <: [_$8, _$9] => Any] => Any)]

[OlivierBlanvillain]

Reproduced, thanks for reporting!

[OlivierBlanvillain]

This is a regression introduced by #2204

[smarter]

Minimized to not require case class:

object Test {
  type Snd[t[_[_, _]]] = t[[a, b] => b]

  class Witness[t[_[_, _]]](value: Snd[t]) {
    def foo[t[_[_, _]]](value: Snd[t] = value) = {}
  }
}

-- [E007] Type Mismatch Error: try/i2219.scala ---------------------------------
4 |    def foo[t[_[_, _]]](value: Snd[t] = value) = {}
  |                                        ^^^^^
  |              found:    Test.Snd[t](Witness.this.value)
  |              required: Test.Snd[(? <: [_$7 <: [_$8, _$9] => Any] => Any)]