Prohibit non-inner classes in enum entries since 1.3

compiler/frontend/src/org/jetbrains/kotlin/resolve/ModifiersChecker.java

@@ -20,6 +20,7 @@ import com.google.common.collect.Maps;
 import com.intellij.psi.PsiElement;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.kotlin.config.LanguageFeature;
 import org.jetbrains.kotlin.config.LanguageVersionSettings;
 import org.jetbrains.kotlin.descriptors.*;
 import org.jetbrains.kotlin.diagnostics.DiagnosticFactory1;
@@ -202,6 +203,17 @@ public class ModifiersChecker {
                 return;
             }
 
+            // Since 1.3, enum entries can contain inner classes only.
+            // Companion objects are reported in ModifierCheckerCore.
+            if (DescriptorUtils.isEnumEntry(containingClass) && !classDescriptor.isInner() && kind != DetailedClassKind.COMPANION_OBJECT) {
+                DiagnosticFactory1<KtClassOrObject, String> diagnostic =
+                        languageVersionSettings.supportsFeature(LanguageFeature.NestedClassesInEnumEntryShouldBeInner)
+                        ? NESTED_CLASS_NOT_ALLOWED
+                        : NESTED_CLASS_NOT_ALLOWED_SINCE_1_3;
+                trace.report(diagnostic.on(ktClassOrObject, kind.withCapitalFirstLetter));
+                return;
+            }
+
             if (!classDescriptor.isInner() && (containingClass.isInner() || DescriptorUtils.isLocal(containingClass))) {
                 trace.report(NESTED_CLASS_NOT_ALLOWED.on(ktClassOrObject, kind.withCapitalFirstLetter));
             }

compiler/testData/diagnostics/tests/classObjects/InnerClassAccessThroughEnum.kt

@@ -3,13 +3,13 @@ package a
 
 enum class C {
     E1, E2, E3 {
-        object O_O
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>object O_O<!>
 
         fun b() {
             O_O
         }
 
-        class G
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>class G<!>
     },
 
     E4 {

compiler/testData/diagnostics/tests/enum/dontCreatePackageTypeForEnumEntry.kt

@@ -1,7 +1,7 @@
 enum class E {
     FIRST,
     SECOND {
-        class A
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>class A<!>
     };
 }
 

compiler/testData/diagnostics/tests/enum/inner/insideEnumEntry.kt

@@ -1,6 +1,6 @@
 enum class E {
     ABC {
-        enum class F {
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>enum class F<!> {
             DEF
         }
     }

compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv11.kt

@@ -1,16 +1,16 @@
-// !LANGUAGE: -InnerClassInEnumEntryClass
+// !LANGUAGE: -InnerClassInEnumEntryClass -NestedClassesInEnumEntryShouldBeInner
 
 enum class Enum {
     ENTRY_WITH_CLASS {
         <!WRONG_MODIFIER_CONTAINING_DECLARATION!>inner<!> class TestInner
 
-        class TestNested
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>class TestNested<!>
 
-        interface TestInterface
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>interface TestInterface<!>
 
-        object TestObject
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>object TestObject<!>
 
-        enum class TestEnumClass {
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>enum class TestEnumClass<!> {
             OTHER_ENTRY
         }
 

compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv12.kt

@@ -1,16 +1,16 @@
-// !LANGUAGE: +InnerClassInEnumEntryClass
+// !LANGUAGE: +InnerClassInEnumEntryClass -NestedClassesInEnumEntryShouldBeInner
 
 enum class Enum {
     ENTRY_WITH_CLASS {
         inner class TestInner
 
-        class TestNested
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>class TestNested<!>
 
-        interface TestInterface
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>interface TestInterface<!>
 
-        object TestObject
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>object TestObject<!>
 
-        enum class TestEnumClass {
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>enum class TestEnumClass<!> {
             OTHER_ENTRY
         }
 

compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv13.kt

@@ -0,0 +1,19 @@
+// !LANGUAGE: +InnerClassInEnumEntryClass +NestedClassesInEnumEntryShouldBeInner
+
+enum class Enum {
+    ENTRY_WITH_CLASS {
+        inner class TestInner
+
+        <!NESTED_CLASS_NOT_ALLOWED!>class TestNested<!>
+
+        <!NESTED_CLASS_NOT_ALLOWED!>interface TestInterface<!>
+
+        <!NESTED_CLASS_NOT_ALLOWED!>object TestObject<!>
+
+        <!NESTED_CLASS_NOT_ALLOWED!>enum class TestEnumClass<!> {
+            OTHER_ENTRY
+        }
+
+        <!WRONG_MODIFIER_CONTAINING_DECLARATION!>companion<!> object {}
+    }
+}

compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv13.txt

@@ -0,0 +1,20 @@
+package
+
+public final enum class Enum : kotlin.Enum<Enum> {
+    enum entry ENTRY_WITH_CLASS
+
+    private constructor Enum()
+    public final override /*1*/ /*fake_override*/ val name: kotlin.String
+    public final override /*1*/ /*fake_override*/ val ordinal: kotlin.Int
+    protected final override /*1*/ /*fake_override*/ fun clone(): kotlin.Any
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: Enum): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    protected/*protected and package*/ final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun finalize(): kotlin.Unit
+    public final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun getDeclaringClass(): java.lang.Class<Enum!>!
+    public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    // Static members
+    public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): Enum
+    public final /*synthesized*/ fun values(): kotlin.Array<Enum>
+}

compiler/testData/diagnostics/tests/inner/nestedClassNotAllowed.kt

@@ -20,6 +20,6 @@ fun foo() {
 enum class E {
     E1 {
         // Not allowed in Java, but no reason to disallow in Kotlin
-        class D
+        <!NESTED_CLASS_NOT_ALLOWED_SINCE_1_3!>class D<!>
     }
 }

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -11872,6 +11872,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("innerClassInEnumEntryClass_lv13.kt")
+            public void testInnerClassInEnumEntryClass_lv13() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv13.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("InnerClassNameClash.kt")
             public void testInnerClassNameClash() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inner/InnerClassNameClash.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -11872,6 +11872,12 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 doTest(fileName);
             }
 
+            @TestMetadata("innerClassInEnumEntryClass_lv13.kt")
+            public void testInnerClassInEnumEntryClass_lv13() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv13.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("InnerClassNameClash.kt")
             public void testInnerClassNameClash() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inner/InnerClassNameClash.kt");

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -63,6 +63,7 @@ enum class LanguageFeature(
     CallableReferencesToClassMembersWithEmptyLHS(KOTLIN_1_2),
 
     RestrictionOfValReassignmentViaBackingField(KOTLIN_1_3),
+    NestedClassesInEnumEntryShouldBeInner(KOTLIN_1_3),
 
     // Experimental features