Incorrect "Wrong number of argument patterns" error for Option extractor using Tuple.Map

[eejbyfeldt]

Compiler version

3.6.4

Minimized code

object Test {
  object E1 {
    def unapply(x: Int): Some[Tuple.Map[(Int, Int), Option]] = ???
  }

  val s: Int = ???
  s match {
    case E1(x, y) => x
  }
}

Output

$ scalac unapply_matchtype.scala 
-- [E107] Syntax Error: unapply_matchtype.scala:10:11 ----------------------------------------
10 |    case E1(x, y) => x
   |         ^^^^^^^^
   | Wrong number of argument patterns for Test.E1; expected: ((Option[Int], Option[Int]))
   |
   | longer explanation available when compiling with `-explain`
1 error found

Expectation

Code should compile without warnings or errors.

Dropping the Option in the return type makes the code work. So the following code compiles

object Test {
  object E1 {
    def unapply(x: Int): Tuple.Map[(Int, Int), Option] = ???
  }

  val s: Int = ???
  s match {
    case E1(x, y) => x
  }
}

But can not be used a general fix at that will run into #22355 in generic code.