KT-6349 J2K: Static members of enums should be converted to class object members

#KT-6349 Fixed

j2k/src/org/jetbrains/kotlin/j2k/ClassBodyConverter.kt

@@ -16,27 +16,15 @@
 
 package org.jetbrains.kotlin.j2k
 
-import com.intellij.psi.PsiClass
-import java.util.HashSet
-import com.intellij.psi.PsiMember
-import java.util.LinkedHashMap
-import com.intellij.psi.PsiAnnotationMethod
-import java.util.ArrayList
-import com.intellij.psi.PsiModifier
-import com.intellij.psi.PsiMethod
+import com.intellij.openapi.util.text.StringUtil
+import com.intellij.psi.*
 import org.jetbrains.kotlin.j2k.ast.*
 import org.jetbrains.kotlin.j2k.ast.Class
-import com.intellij.psi.PsiField
-import com.intellij.psi.PsiReturnStatement
-import com.intellij.psi.PsiReferenceExpression
-import com.intellij.openapi.util.text.StringUtil
-import java.util.HashMap
-import com.intellij.psi.PsiClassInitializer
-import com.intellij.psi.PsiExpressionStatement
-import com.intellij.psi.PsiAssignmentExpression
-import com.intellij.psi.PsiExpression
-import com.intellij.psi.JavaTokenType
 import org.jetbrains.kotlin.j2k.usageProcessing.AccessorToPropertyProcessing
+import java.util.ArrayList
+import java.util.HashMap
+import java.util.HashSet
+import java.util.LinkedHashMap
 
 class FieldCorrectionInfo(val name: String, val access: Modifier?, val setterAccess: Modifier?) {
     val identifier = Identifier(name).assignNoPrototype()
@@ -97,7 +85,7 @@ class ClassBodyConverter(private val psiClass: PsiClass,
                 primaryConstructorSignature = member.createSignature(converter)
                 members.add(member.initializer())
             }
-            else if (useCompanionObject && member !is Class && psiMember.hasModifierProperty(PsiModifier.STATIC)) {
+            else if (useCompanionObject && member !is Class && psiMember !is PsiEnumConstant && psiMember.hasModifierProperty(PsiModifier.STATIC)) {
                 companionObjectMembers.add(member)
             }
             else {
@@ -131,10 +119,8 @@ class ClassBodyConverter(private val psiClass: PsiClass,
 
     // do not convert private static methods into companion object if possible
     private fun shouldGenerateCompanionObject(convertedMembers: Map<PsiMember, Member>): Boolean {
-        if (psiClass.isEnum()) return false
-
         val members = convertedMembers.keySet().filter { !it.isConstructor() }
-        val companionObjectMembers = members.filter { it !is PsiClass && it.hasModifierProperty(PsiModifier.STATIC) }
+        val companionObjectMembers = members.filter { it !is PsiClass && it !is PsiEnumConstant && it.hasModifierProperty(PsiModifier.STATIC) }
         val nestedClasses = members.filterIsInstance<PsiClass>().filter { it.hasModifierProperty(PsiModifier.STATIC) }
         if (companionObjectMembers.all { it is PsiMethod && it.hasModifierProperty(PsiModifier.PRIVATE) }) {
             return nestedClasses.any { nestedClass -> companionObjectMembers.any { converter.referenceSearcher.findMethodCalls(it as PsiMethod, nestedClass).isNotEmpty() } }

j2k/testData/fileOrElement/enum/companionObject.java

@@ -0,0 +1,12 @@
+public enum TestEnum {
+    A,
+    B;
+
+    public static TestEnum parse() { return A; }
+}
+
+class Go {
+    void fn() {
+        TestEnum x = TestEnum.parse();
+    }
+}

j2k/testData/fileOrElement/enum/companionObject.kt

@@ -0,0 +1,17 @@
+public enum class TestEnum {
+    A
+    B
+
+    companion object {
+
+        public fun parse(): TestEnum {
+            return A
+        }
+    }
+}
+
+class Go {
+    fun fn() {
+        val x = TestEnum.parse()
+    }
+}

j2k/tests/org/jetbrains/kotlin/j2k/JavaToKotlinConverterForWebDemoTestGenerated.java

@@ -1645,6 +1645,12 @@ public class JavaToKotlinConverterForWebDemoTestGenerated extends AbstractJavaTo
             doTest(fileName);
         }
 
+        @TestMetadata("companionObject.java")
+        public void testCompanionObject() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/enum/companionObject.java");
+            doTest(fileName);
+        }
+
         @TestMetadata("emptyEnum.java")
         public void testEmptyEnum() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/enum/emptyEnum.java");

j2k/tests/org/jetbrains/kotlin/j2k/JavaToKotlinConverterSingleFileTestGenerated.java

@@ -1645,6 +1645,12 @@ public class JavaToKotlinConverterSingleFileTestGenerated extends AbstractJavaTo
             doTest(fileName);
         }
 
+        @TestMetadata("companionObject.java")
+        public void testCompanionObject() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/enum/companionObject.java");
+            doTest(fileName);
+        }
+
         @TestMetadata("emptyEnum.java")
         public void testEmptyEnum() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/enum/emptyEnum.java");