[FE] Check if type variable is fixed into an empty intersection type and report resolution warnings/errors if needed (completion stage)

^KT-51221 Fixed

core/descriptors/src/org/jetbrains/kotlin/types/checker/ClassicTypeSystemContext.kt

@@ -460,6 +460,10 @@ interface ClassicTypeSystemContext : TypeSystemInferenceExtensionContext, TypeSy
         return makeSimpleTypeDefinitelyNotNullOrNotNullInternal(this)
     }
 
+    override fun KotlinTypeMarker.isFinal(): Boolean {
+        require(this is KotlinType, this::errorMessage)
+        return !TypeUtils.canHaveSubtypes(KotlinTypeChecker.DEFAULT, this)
+    }
 
     override fun KotlinTypeMarker.removeAnnotations(): KotlinTypeMarker {
         require(this is UnwrappedType, this::errorMessage)