Kapt: Don't convert field initializers for enum fields inside companion objects (KT-37732)

For classes with companion objects, Kotlin compiler generates a 'Companion' static accessor field.
Java prioritizes fields over inner types (apparently, Scala does this as well, KT-29864), so the generated initializer doesn't compile.
As a workaround, initializer generatation is disabled for enum fields inside companion objects. Certainly, it's not a proper fix, however it does fix the regression.

plugins/kapt3/kapt3-compiler/src/org/jetbrains/kotlin/kapt3/stubs/ClassFileToSourceStubConverter.kt

@@ -60,10 +60,12 @@ import org.jetbrains.kotlin.resolve.constants.evaluate.ConstantExpressionEvaluat
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameOrNull
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.getSuperClassOrAny
+import org.jetbrains.kotlin.resolve.descriptorUtil.isCompanionObject
 import org.jetbrains.kotlin.resolve.source.PsiSourceElement
 import org.jetbrains.kotlin.types.ErrorUtils
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.isError
+import org.jetbrains.kotlin.types.typeUtil.isEnum
 import org.jetbrains.org.objectweb.asm.Opcodes
 import org.jetbrains.org.objectweb.asm.Type
 import org.jetbrains.org.objectweb.asm.tree.*
@@ -668,6 +670,18 @@ class ClassFileToSourceStubConverter(val kaptContext: KaptContextForStubGenerati
         }
 
         val propertyType = (origin?.descriptor as? PropertyDescriptor)?.returnType
+
+        /*
+            Work-around for enum classes in companions.
+            In expressions "Foo.Companion.EnumClass", Java prefers static field over a type name, making the reference invalid.
+        */
+        if (propertyType != null && propertyType.isEnum()) {
+            val enumClass = propertyType.constructor.declarationDescriptor
+            if (enumClass is ClassDescriptor && enumClass.isInsideCompanionObject()) {
+                return null
+            }
+        }
+
         if (propertyInitializer != null && propertyType != null) {
             val constValue = getConstantValue(propertyInitializer, propertyType)
             if (constValue != null) {
@@ -686,6 +700,15 @@ class ClassFileToSourceStubConverter(val kaptContext: KaptContextForStubGenerati
         return null
     }
 
+    private fun DeclarationDescriptor.isInsideCompanionObject(): Boolean {
+        val parent = containingDeclaration ?: return false
+        if (parent.isCompanionObject()) {
+            return true
+        }
+
+        return parent.isInsideCompanionObject()
+    }
+
     private object UnknownConstantValue
 
     private fun getConstantValue(expression: KtExpression, expectedType: KotlinType): ConstantValue<*>? {

plugins/kapt3/kapt3-compiler/test/org/jetbrains/kotlin/kapt3/test/ClassFileToSourceStubConverterTestGenerated.java

@@ -108,6 +108,11 @@ public class ClassFileToSourceStubConverterTestGenerated extends AbstractClassFi
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/enumImports.kt");
     }
 
+    @TestMetadata("enumInCompanion.kt")
+    public void testEnumInCompanion() throws Exception {
+        runTest("plugins/kapt3/kapt3-compiler/testData/converter/enumInCompanion.kt");
+    }
+
     @TestMetadata("enums.kt")
     public void testEnums() throws Exception {
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/enums.kt");

plugins/kapt3/kapt3-compiler/test/org/jetbrains/kotlin/kapt3/test/IrClassFileToSourceStubConverterTestGenerated.java

@@ -109,6 +109,11 @@ public class IrClassFileToSourceStubConverterTestGenerated extends AbstractIrCla
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/enumImports.kt");
     }
 
+    @TestMetadata("enumInCompanion.kt")
+    public void testEnumInCompanion() throws Exception {
+        runTest("plugins/kapt3/kapt3-compiler/testData/converter/enumInCompanion.kt");
+    }
+
     @TestMetadata("enums.kt")
     public void testEnums() throws Exception {
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/enums.kt");

plugins/kapt3/kapt3-compiler/testData/converter/enumInCompanion.kt

@@ -0,0 +1,45 @@
+class Test {
+    private val foo = Example.FOO
+
+    companion object {
+        enum class Example { FOO }
+    }
+}
+
+class Test2 {
+    private val foo = Example.FOO
+
+    companion object Amigo {
+        enum class Example { FOO }
+    }
+}
+
+class Test3 {
+    private val foo = Amigo.Example.FOO
+
+    object Amigo {
+        enum class Example { FOO }
+    }
+}
+
+class Test4 {
+    private val foo = Foo.constProperty
+
+    companion object {
+        object Foo {
+            const val constProperty = 1
+        }
+    }
+}
+
+class Test5 {
+    private val foo = Amigos.Companion.Goo.Example.FOO
+
+    class Amigos {
+        companion object {
+            class Goo {
+                enum class Example { FOO }
+            }
+        }
+    }
+}

plugins/kapt3/kapt3-compiler/testData/converter/enumInCompanion.txt

@@ -0,0 +1,175 @@
+import java.lang.System;
+
+@kotlin.Metadata()
+public final class Test {
+    private final Test.Companion.Example foo;
+    @org.jetbrains.annotations.NotNull()
+    public static final Test.Companion Companion = null;
+
+    public Test() {
+        super();
+    }
+
+    @kotlin.Metadata()
+    public static final class Companion {
+
+        private Companion() {
+            super();
+        }
+
+        @kotlin.Metadata()
+        public static enum Example {
+            /*public static final*/ FOO /* = new Example() */;
+
+            Example() {
+            }
+        }
+    }
+}
+
+////////////////////
+
+
+import java.lang.System;
+
+@kotlin.Metadata()
+public final class Test2 {
+    private final Test2.Amigo.Example foo;
+    @org.jetbrains.annotations.NotNull()
+    public static final Test2.Amigo Amigo = null;
+
+    public Test2() {
+        super();
+    }
+
+    @kotlin.Metadata()
+    public static final class Amigo {
+
+        private Amigo() {
+            super();
+        }
+
+        @kotlin.Metadata()
+        public static enum Example {
+            /*public static final*/ FOO /* = new Example() */;
+
+            Example() {
+            }
+        }
+    }
+}
+
+////////////////////
+
+
+import java.lang.System;
+
+@kotlin.Metadata()
+public final class Test3 {
+    private final Test3.Amigo.Example foo = Test3.Amigo.Example.FOO;
+
+    public Test3() {
+        super();
+    }
+
+    @kotlin.Metadata()
+    public static final class Amigo {
+        @org.jetbrains.annotations.NotNull()
+        public static final Test3.Amigo INSTANCE = null;
+
+        private Amigo() {
+            super();
+        }
+
+        @kotlin.Metadata()
+        public static enum Example {
+            /*public static final*/ FOO /* = new Example() */;
+
+            Example() {
+            }
+        }
+    }
+}
+
+////////////////////
+
+
+import java.lang.System;
+
+@kotlin.Metadata()
+public final class Test4 {
+    private final int foo = 1;
+    @org.jetbrains.annotations.NotNull()
+    public static final Test4.Companion Companion = null;
+
+    public Test4() {
+        super();
+    }
+
+    @kotlin.Metadata()
+    public static final class Companion {
+
+        private Companion() {
+            super();
+        }
+
+        @kotlin.Metadata()
+        public static final class Foo {
+            public static final int constProperty = 1;
+            @org.jetbrains.annotations.NotNull()
+            public static final Test4.Companion.Foo INSTANCE = null;
+
+            private Foo() {
+                super();
+            }
+        }
+    }
+}
+
+////////////////////
+
+
+import java.lang.System;
+
+@kotlin.Metadata()
+public final class Test5 {
+    private final Test5.Amigos.Companion.Goo.Example foo;
+
+    public Test5() {
+        super();
+    }
+
+    @kotlin.Metadata()
+    public static final class Amigos {
+        @org.jetbrains.annotations.NotNull()
+        public static final Test5.Amigos.Companion Companion = null;
+
+        public Amigos() {
+            super();
+        }
+
+        @kotlin.Metadata()
+        public static final class Companion {
+
+            private Companion() {
+                super();
+            }
+
+            @kotlin.Metadata()
+            public static final class Goo {
+
+                public Goo() {
+                    super();
+                }
+
+                @kotlin.Metadata()
+                public static enum Example {
+                    /*public static final*/ FOO /* = new Example() */;
+
+                    Example() {
+                    }
+                }
+            }
+        }
+    }
+}