Unification of type alias inconsistent between class and def

[scabug]

scala> class Foo[S] { type X = List[S]; val x: X = List() }
defined class Foo

scala> new Foo[Int].x : List[Int]
res0: List[Int] = List()

scala> def foo[S] = { type X = List[S]; List():X }
foo: [S]=> X

scala> foo[Int] : List[Int]
<console>:9: error: type mismatch;
 found   : X
    (which expands to)  List[S]
 required: List[Int]
              foo[Int] : List[Int]
                 ^

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-7038?orig=1
Reporter: Runar (runar)
Affected Versions: 2.9.1, 2.10.0

[scabug]

@retronym said:
@adriaan: here's a patch for discussion: retronym/scala#3

[SethTisue]

Scala 3.3.1 accepts it.