Do not suggest "Make overridden member open" for already open ones

So #KT-18148 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/MakeOverriddenMemberOpenFix.kt

@@ -57,7 +57,8 @@ class MakeOverriddenMemberOpenFix(declaration: KtDeclaration) : KotlinQuickFixAc
         for (overriddenDescriptor in getAllDeclaredNonOverridableOverriddenDescriptors(descriptor)) {
             assert(overriddenDescriptor.kind == DECLARATION) { "Can only be applied to declarations." }
             val overriddenMember = DescriptorToSourceUtils.descriptorToDeclaration(overriddenDescriptor)
-            if (overriddenMember == null || !overriddenMember.canRefactor() || overriddenMember !is KtCallableDeclaration) {
+            if (overriddenMember == null || !overriddenMember.canRefactor() || overriddenMember !is KtCallableDeclaration ||
+                overriddenMember.modifierList?.hasModifier(OPEN_KEYWORD) == true) {
                 return false
             }
             val containingDeclarationName = overriddenDescriptor.containingDeclaration.name.asString()

idea/testData/quickfix/override/overridingOpenMethodInFinalClass.kt

@@ -0,0 +1,11 @@
+// "Make A.foo open" "false"
+// ACTION: Convert to expression body
+// ERROR: 'foo' in 'A' is final and cannot be overridden
+// ERROR: This type is final, so it cannot be inherited from
+class A() {
+    open fun foo() {}
+}
+
+class B : A() {
+    override<caret> fun foo() { }
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -7505,6 +7505,12 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
             doTest(fileName);
         }
 
+        @TestMetadata("overridingOpenMethodInFinalClass.kt")
+        public void testOverridingOpenMethodInFinalClass() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/override/overridingOpenMethodInFinalClass.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("parameterNameChangedAmbiguousRename.kt")
         public void testParameterNameChangedAmbiguousRename() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/override/parameterNameChangedAmbiguousRename.kt");