Forbid case classes without parameter lists?

[LPTK]

Scalac rejects case classes such as:

@ case class A[T]
(console):1: case classes must have a parameter list; try 'case class A()' or 'case object A'
case class A[T]
               ^

Dotty currently accepts them. This can be confusing in pattern matching: it looks like pattern case A => is matching on instances of class A, but it's actually matching on the companion object.

[smarter]

Yes, we should emit the same error as scalac here.

[ashwinbhaskar]

@smarter can I give this a shot? If so, can you please assign it to me as well.

[LPTK]

BTW, you should make sure that enum A { case B[C] } has the same treatment.

[ashwinbhaskar]

@LPTK should this be allowed?

enum A { case B }

[LPTK]

@ashwinbhaskar yes, that's just a case value. You refer to it and match it as B, so there is no confusion here.

[ashwinbhaskar]

@OlivierBlanvillain can the fix be merged now?