Allow some kindness in provablyDisjoint

Author: dwijnand

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

@@ -2841,8 +2841,9 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
       case (tp1: TypeRef, tp2: TypeRef) if tp1.symbol.isClass && tp2.symbol.isClass =>
         val cls1 = tp1.classSymbol
         val cls2 = tp2.classSymbol
+        val sameKind = tp1.hasSameKindAs(tp2)
         def isDecomposable(sym: Symbol, tp: Type): Boolean =
-          tp.hasSimpleKind && sym.is(Sealed) && !sym.hasAnonymousChild
+          sameKind && sym.is(Sealed) && !sym.hasAnonymousChild
         def decompose(sym: Symbol, tp: Type): List[Type] =
           sym.children.map(x => refineUsingParent(tp, x)).filter(_.exists)
         if (cls1.derivesFrom(cls2) || cls2.derivesFrom(cls1))