Spurious deprecation when using type/value alias pair

[lrytz]

On 2.13.14:

scala> @deprecated case class C(x: Int)
class C

scala> object A { type X = C; val X = C }
                           ^
       warning: class C is deprecated
object A

scala> new A.X(10) // no deprecation
val res0: C = C(10)

scala> A.X.toString // no deprecation
val res1: String = C

scala> A.X.apply(10) // spurious deprecation
           ^
       warning: class C is deprecated
val res2: C = C(10)

The warning is actually issued while performing transformCaseApply, which happens during refchecks. 2.12 doesn't warn because the compiler doesn't see through the alias and doesn't trigger the transformCaseApply optimization.

[lrytz]

For the record, Scala 3 already warns one line earlier...

scala> @deprecated case class C(x: Int)
// defined case class C

scala> object A { type X = C; val X = C }
1 warning found
-- Deprecation Warning: --------------------------------------------------------
1 |object A { type X = C; val X = C }
  |                    ^
  |                    class C is deprecated
// defined object A

scala> new A.X(10) // no deprecation
val res2: C = C(10)

scala> A.X.toString // spurious deprecation
1 warning found
-- Deprecation Warning: --------------------------------------------------------
1 |A.X.toString // spurious deprecation
  |^^^^^^^^^^^^
  |class C is deprecated
val res3: String = C

scala> A.X.apply(10) // spurious deprecation
1 warning found
-- Deprecation Warning: --------------------------------------------------------
1 |A.X.apply(10) // spurious deprecation
  |^^^^^^^^^
  |class C is deprecated
val res4: C = C(10)

That must be yet another feature interaction. It's not that Scala 3 generally looks through aliases to find deprecations. type Alias = DeprecatedClass; new Alias doesn't warn.