Definitions within Enum should report errors

Compiler version

Latest dotty on Scastie (3.2.0-RC1)

Minimized code

enum MyEnum {
  case class Foo(n: Int)

  case Constructor(field: Foo)
}

Output

enum MyEnum {
  case class Foo(n: Int)

  case Constructor(field: Foo)
  // Not found: type Foo  ^^^
}

Expectation

If definitions within enums cannot be referred to, they should be forbidden. The error message in this case should be something along the lines of:

enum MyEnum {
  case class Foo(n: Int)
 // case class definitions in enum not allowed. 

  case Constructor(field: Foo) 
}

[som-snytt]

The example at the doc link includes putting the member in the companion and how to reference it.

I agree it’s unfortunately confusing.

[odersky]

I think the docs already do a fairly decent job here but if someone has an idea how to improve them a suggestion or PR would be welcome.

About the error message: this will be tricky. The case class generated from case Foo is put in the companion object before Typer. So we see what we see in the companion object during typer. We could improve this only by turning the compiler more into a BBoM (big ball of mud) by merging desugaring and typing for enums.