Address review

Author: OlivierBlanvillain

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

@@ -744,7 +744,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
     }
 
     def tryBaseType(cls2: Symbol) = {
-      val allowBaseType = caseLambda.eq(NoType) || (tp1 match {
+      val allowBaseType = !caseLambda.exists || (tp1 match {
         case tp: TypeRef if tp.symbol.isClass => true
         case AppliedType(tycon: TypeRef, _) if tycon.symbol.isClass => true
         case _ => false
@@ -769,7 +769,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
                 || narrowGADTBounds(tp1, tp2, approx, isUpper = true))
               && (tp2.isAny || GADTusage(tp1.symbol))
 
-            caseLambda.eq(NoType) && isSubType(hi1, tp2, approx.addLow) || compareGADT || tryLiftedToThis1
+            !caseLambda.exists && isSubType(hi1, tp2, approx.addLow) || compareGADT || tryLiftedToThis1
           case _ =>
             // `Mode.RelaxedOverriding` is only enabled when checking Java overriding
             // in explicit nulls, and `Null` becomes a bottom type, which allows
@@ -2540,7 +2540,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
     def fullyInstantiated(tp: Type): Boolean = new TypeAccumulator[Boolean] {
       override def apply(x: Boolean, t: Type) =
         x && {
-          t match {
+          t.dealias match {
             case tp: TypeRef if !tp.symbol.isClass => false
             case _: SkolemType | _: TypeVar | _: TypeParamRef => false
             case _ => foldOver(x, t)