Type argument error shows _

[Adam-Vandervorst]

Compiler version

3.1.2-RC1-bin-20211025-968dd1b-NIGHTLY

Minimized code

type ToInt[X] = Int

@main def example =
  val xs = (???, ???)

  xs.map[ToInt]([C] => (x1: C) => x1 match {
    case x2: ([V] => () => Int) =>
      x2[Int]()
    case _ => 42
  })

Output

     x2[Int]()
         ^
        Type argument Int does not conform to upper bound _

Expectation

When trying to find a workaround to #13918, I stumbled across this weird error.
It seems like the _ should not be there, and if it should, I don't find the documentation on it.

[ckipp01]

Note that the error here is different now as of 3.3.1-RC1-bin-20230514-b0ccf40-NIGHTLY.

[warn] ./example.scala:12:16
[warn] the type test for [V] => () => Int cannot be checked at runtime because it's a refinement type
[warn]           case x2: ([V] => () => Int) =>
[warn]                ^
Compiled project (Scala 3.3.1-RC1-bin-20230514-b0ccf40-NIGHTLY, JVM)