open is not treated as a normal identifier inside match

[andrelfpinto]

Compiler version

3.1.3

Minimized code

class Foo(open: String) {
  def bar(n: Int) = n match {
    case 0 => open
    case _ => throw new IndexOutOfBoundsException()
  }
  def baz() = open
}

Output

-- [E088] Syntax Error: Open.scala:4:4 ----------------------------------------------------
4 |    case _ => throw new IndexOutOfBoundsException()
  |    ^^^^
  |    Expected start of definition

Explanation
===========
You have to provide either class, trait, object, or enum definitions after qualifiers

1 error found

Expectation

bar should compile as baz does.

According to this:

open is a soft modifier. It is treated as a normal identifier unless it is in modifier position.

It seems like open is not being treated as a normal identifier inside match.

[som-snytt]

It needs to work a bit harder to disambiguate case.

class Foo(open: String):
  def bar(n: Int) = n match
    case 0 => open case class C(); ???
    case 1 => case class K(); ???
    case _ => throw new IndexOutOfBoundsException()
  def baz() = { open class D; () }

It says

Modifier open is redundant for this definition

but not illegal.