Only private constructors for sealed / enum classes #KT-12377 Fixed

Also #KT-8497 Fixed

idea/idea-core/src/org/jetbrains/kotlin/idea/core/psiModificationUtils.kt

@@ -198,18 +198,21 @@ fun KtModifierListOwner.setVisibility(visibilityModifier: KtModifierKeywordToken
     addModifier(visibilityModifier)
 }
 
-fun KtDeclaration.implicitVisibility(): KtModifierKeywordToken? {
-    val defaultVisibilityKeyword = if (hasModifier(KtTokens.OVERRIDE_KEYWORD)) {
-        (resolveToDescriptor() as? CallableMemberDescriptor)
-                ?.overriddenDescriptors
-                ?.let { OverridingUtil.findMaxVisibility(it) }
-                ?.toKeywordToken()
-    }
-    else {
-        KtTokens.DEFAULT_VISIBILITY_KEYWORD
-    }
-    return defaultVisibilityKeyword
-}
+fun KtDeclaration.implicitVisibility(): KtModifierKeywordToken? =
+        if (this is KtConstructor<*>) {
+            val klass = getContainingClassOrObject()
+            if (klass is KtClass && (klass.isEnum() || klass.isSealed())) KtTokens.PRIVATE_KEYWORD
+            else KtTokens.DEFAULT_VISIBILITY_KEYWORD
+        }
+        else if (hasModifier(KtTokens.OVERRIDE_KEYWORD)) {
+            (resolveToDescriptor() as? CallableMemberDescriptor)
+                    ?.overriddenDescriptors
+                    ?.let { OverridingUtil.findMaxVisibility(it) }
+                    ?.toKeywordToken()
+        }
+        else {
+            KtTokens.DEFAULT_VISIBILITY_KEYWORD
+        }
 
 fun KtModifierListOwner.canBePrivate(): Boolean {
     if (modifierList?.hasModifier(KtTokens.ABSTRACT_KEYWORD) ?: false) return false