Wrong staging level when accessing type from class

[biboudis]

When:

class F[T: Type] { '(null.asInstanceOf[T]) }

access to T from the class F is reported as a wrong level:

4 |  '(null.asInstanceOf[T])
  |                      ^
  |                      access to F.this from wrong staging level:
  |                       - the definition is at level 0,
  |                       - but the access is at level 1.

SImilarly:

class F {
  type T
  '(null.asInstanceOf[T])
}

[Blaisorblade]

Isn't that correct in the absence of lifting for types? Introducing it makes sense, but last time this came up (while talking to @nicolasstucki during a meeting) there weren't rules for it.

[nicolasstucki]

The problem is that it is the prefix of the type that gets the error. If we add the implicit Type[T] we still get this error. The code snippet should probably have the implicit type evidence.

[nicolasstucki]

With prefix I referred to Foo.this in Foo.this.T which is the type of T.

[biboudis]

Yes, I updated it to avoid any misconceptions.

[Blaisorblade]

Oh dear. That's because references to type params are still TypeRefs rather than TypeParamRefs? I am fine with that encoding, but that suggests that (for the theory) that classes need to exist in multiple phases?
EDIT:
Just confirmed, this happens in ReifyQuotes.check, which checks type T encoded as
TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class F)),type T), which then recurses on ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <empty>)),class F)).

[biboudis]

Yeap. 😏