`GADT constraints with pattern alternatives` compile error since Scala 3.7.1

[xuwei-k]

Compiler version

3.7.1
(not 3.7.0, 3.3.6)

Minimized code

//> using scala 3.7.1

package example

sealed trait A[X, Y]
case class B[X](x: X) extends A[X, Int]
case class C[X](x: X) extends A[X, Int]
case class D[X, Y](x: X, y: Y) extends A[X, Y]

def f[X, Y](a: A[X, Y]): Y = a match {
  case B(_) | C(_) => 2
  case D(_, y) => y
}

Output

[error] ./A.scala:11:23
[error] Found:    (2 : Int)
[error] Required: Y
[error]   case B(_) | C(_) => 2
[error]                       ^

Expectation

success

Note

• maybe Fix: Prevent GADT reasoning in pattern alternatives #22853 Unsound GADT constraints with pattern alternatives #22805 ? 🤔

[xuwei-k]

success 3.7.2-RC1-bin-20250603-0be2091-NIGHTLY

• Improve GADT reasoning for pattern alternatives #23205 🤔