Type member in subclass should shadow type member in owner

[japgolly]

Compiler version

3.0.0-RC1

Minimized code

trait X { type M = Int }

object Y {
  type M = String

  class C extends X {
    def m: M = 123
  }
}

Output

7 |    def m: M = 123
  |           ^
  |           Reference to M is ambiguous,
  |           it is both defined in object Y
  |           and inherited subsequently in class C

Expectation

It should compile. (It does in Scala 2.x)

[smarter]

This is an intentional change in what constitutes shadowing: #8622 (the backstory is scala/bug#11921)

[japgolly]

Ah ok cool thanks