Fix overriding check

Author: noti0na1

compiler/src/dotty/tools/dotc/cc/Setup.scala

@@ -117,7 +117,6 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
    *  The info of these symbols is made fluid.
    */
   def isPreCC(sym: Symbol)(using Context): Boolean =
-    // TODO: check type members as well
     sym.isTerm && sym.maybeOwner.isClass
     && !sym.is(Module)
     && !sym.owner.is(CaptureChecked)

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

@@ -21,6 +21,7 @@ import config.MigrationVersion
 import config.Printers.refcheck
 import reporting.*
 import Constants.Constant
+import cc.stripCapturing
 
 object RefChecks {
   import tpd.*
@@ -83,8 +84,10 @@ object RefChecks {
    *  This one used to succeed only if forwarding parameters is on.
    *  (Forwarding tends to hide problems by binding parameter names).
    */
+
   private def upwardsThisType(cls: Symbol)(using Context) = cls.info match {
-    case ClassInfo(_, _, _, _, tp: Type) if (tp ne cls.typeRef) && !cls.isOneOf(FinalOrModuleClass) =>
+    case ClassInfo(_, _, _, _, tp: Type) if (tp.stripCapturing ne cls.typeRef) && !cls.isOneOf(FinalOrModuleClass) =>
+      // println(i"upwardsThisType($cls) = ${cls.typeRef}, ne $tp")
       SkolemType(cls.appliedRef).withName(nme.this_)
     case _ =>
       cls.thisType
@@ -439,7 +442,7 @@ object RefChecks {
         val (mtp, otp) = if compareTypes then (memberTp(self), otherTp(self)) else (NoType, NoType)
         OverrideError(core, self, member, other, mtp, otp)
 
-      def compatTypes(memberTp: Type, otherTp: Type): Boolean =
+      def compatTypes(memberTp: Type, otherTp: Type): Boolean = // race.force(i"compatTypes $memberTp <:< $otherTp"):
         try
           isOverridingPair(member, memberTp, other, otherTp,
             fallBack = warnOnMigration(

tests/neg-custom-args/captures/i21868b.scala

@@ -29,15 +29,8 @@ class Concrete4(io: IO^) extends Abstract2(io):
   type C = CapSet
   def f(file: File) = ()
 
-// TODO: Should be an error
 class Concrete5(io1: IO^, io2: IO^) extends Abstract2(io1):
-  // Similar to Concrete8, this type member should have overriding error.
-  // Parent class is Abstract2 { val io = Concrete5.this.io1 }
-  // Abstract2.this.C >: CapSet <: CapSet^{Concrete5.this.io1}
-  // Concrete5.this.C = CapSet^{Concrete5.this.io2}
-  // CapSet^{Concrete5.this.io2} !<:< CapSet^{Concrete5.this.io1}
-  // Hence, Concrete5.this.C !<:< Abstract2.this.C
-  type C = CapSet^{io2}
+  type C = CapSet^{io2} // error
   def f(file: File^{io2}) = ()
 
 trait Abstract3[X^]:
@@ -53,5 +46,4 @@ class Concrete7(io1: IO^, io2: IO^) extends Abstract3[CapSet^{io1}]:
   def f(file: File^{io2}) = ()
 
 class Concrete8(io1: IO^, io2: IO^) extends Abstract3[CapSet^{io1}]:
-  type C = CapSet^{io1}
   def f(file: File^{io2}) = () // error