Paths to abstract CapSet members within capture sets are rejected

[bracevac]

Compiler version

Latest NIGHTLY

Minimized code

import language.experimental.captureChecking
import caps._

trait Foo extends Capability

trait CaptureSet:
  type C <: CapSet^

def test =
  val x: Foo^ = ???

  object X extends CaptureSet:
    type C = CapSet^{x}

  val y: Foo^{X.C^} = x // error

Output

-- Error: local/ccpaths.scala:70:15 --------------------------------------------
70 |  val u: Foo^{X.C^} = x
   |              ^^^^
   |X.C is not a legal prefix for `^` here,
   |is must be a type parameter or abstract type with a caps.CapSet upper bound.

Expectation

It should be accepted (+ the error message has a typo).

[bracevac]

@noti0na1

[noti0na1]

def isLegalCapsOfArg =
  arg.symbol.isAbstractOrParamType && arg.symbol.info.derivesFrom(defn.Caps_CapSet)

Changing isAbstractOrParamType to isType will work. Not sure why we had the requirement for abstract type at beginning.