Ignore capturing from parents when computing base type

Author: noti0na1

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -23,7 +23,7 @@ import scala.util.control.NonFatal
 import config.Config
 import reporting.*
 import collection.mutable
-import cc.{CapturingType, derivedCapturingType}
+import cc.{CapturingType, derivedCapturingType, stripCapturing}
 
 import scala.annotation.internal.sharable
 import scala.compiletime.uninitialized
@@ -2232,7 +2232,7 @@ object SymDenotations {
         tp match {
           case tp @ TypeRef(prefix, _) =>
             def foldGlb(bt: Type, ps: List[Type]): Type = ps match {
-              case p :: ps1 => foldGlb(bt & recur(p), ps1)
+              case p :: ps1 => foldGlb(bt & recur(p.stripCapturing), ps1)
               case _ => bt
             }
 

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -895,20 +895,13 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
       canWidenAbstract && acc(true, tp)
 
     def tryBaseType(cls2: Symbol) =
-      var base = nonExprBaseType(tp1, cls2)
+      val base = nonExprBaseType(tp1, cls2)
       if base.exists && (base ne tp1)
           && (!caseLambda.exists
               || widenAbstractOKFor(tp2)
               || tp1.widen.underlyingClassRef(refinementOK = true).exists)
       then
         def checkBase =
-          // Strip existing capturing set from base type
-          base = base.stripCapturing
-          // Pass capture set of tp1 to base type
-          tp1 match
-            case tp1 @ CapturingType(_, refs1) =>
-              base = CapturingType(base, refs1, tp1.isBoxed)
-            case _ =>
           isSubType(base, tp2, if tp1.isRef(cls2) then approx else approx.addLow)
           && recordGadtUsageIf { MatchType.thatReducesUsingGadt(tp1) }
         if tp1.widenDealias.isInstanceOf[AndType] || base.isInstanceOf[OrType] then