Missing inheritance check for Capability classes

[noti0na1]

Compiler version

3.nightly (3.7.2-RC1-bin-20250520-baac46c-NIGHTLY)

Minimized code

import language.experimental.captureChecking
import caps.*

class A:
  def a: A = this

class B extends A, Capability

def leak(b: B): A = b.a

Output

Run: scala compile --server=false -S 3.nightly Stest.scala

Compile success.

Expectation

Reject, as we treat B as impure, and it should fail on inheritance check (maybe by checkSelfAgainstParents)