Compiler version

3.4.1

Minimized code

This test should be changed and pass.

  // file dotty/tools/pc/tests/completion/CompletionSuite.scala
  @Test def pat1 =
    check(
      s"""|object Main {
          |  Option(1) match {
          |    case List(Som@@)
          |}
          |""".stripMargin,
      """|Some(value) scala
         |Some scala
         |""".stripMargin
    )

Output

      """|Some scala
         |Some[A](value: A): Some[A]
         |""".stripMargin

Expectation

Extra unapply completion should be added to the completion list, where it is allowed and completion with expected type parameters should be filtered as it is illegal at this position.
The test should pass.

Tips

My guess is that the root of the issue is in CaseDefCompletions, which is responsible for providing us with extra results. The logic probably matches against specific patterns, but what we should do instead is to recursively try to find whether one of the owners is case definition and all other owners in between are unapply methods.