IntelliJ IDEA CEでGroovy->Javaが出来ないと思ったときにやるべき事

**結論に飛ぶには[ここ](#%E7%B5%90%E8%AB%96)から**

# はじめに
ある日、`Convert Groovy to Java`でGroovyをJavaに変換しようとしたところ、全く動かず。
コード自体に問題はなく、原因不明なのでログを見たところこんなエラーが...

```
java.lang.UnsupportedOperationException
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.TypeWriter.visitDisjunctionType(TypeWriter.java:155)
	at com.intellij.psi.PsiDisjunctionType.accept(PsiDisjunctionType.java:114)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.TypeWriter.writeType(TypeWriter.java:72)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.TypeWriter.writeType(TypeWriter.java:49)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.CodeBlockGenerator.writeVariableWithoutSemicolonAndInitializer(CodeBlockGenerator.java:481)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.CodeBlockGenerator.visitCatchClause(CodeBlockGenerator.java:534)
	at org.jetbrains.plugins.groovy.lang.psi.impl.statements.GrCatchClauseImpl.accept(GrCatchClauseImpl.java:45)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.CodeBlockGenerator.visitTryStatement(CodeBlockGenerator.java:523)
	at org.jetbrains.plugins.groovy.lang.psi.impl.statements.GrTryCatchStatementImpl.accept(GrTryCatchStatementImpl.java:43)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.CodeBlockGenerator.visitStatementOwner(CodeBlockGenerator.java:160)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.CodeBlockGenerator.generateCodeBlock(CodeBlockGenerator.java:152)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.CodeBlockGenerator.generateMethodBody(CodeBlockGenerator.java:119)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.ClassItemGeneratorImpl.writeMethod(ClassItemGeneratorImpl.java:159)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.ClassGenerator.writeAllMethods(ClassGenerator.java:149)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.ClassGenerator.writeMembers(ClassGenerator.java:124)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.ClassGenerator.writeTypeDefinition(ClassGenerator.java:106)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.ConvertToJavaProcessor.performRefactoring(ConvertToJavaProcessor.java:93)
	at com.intellij.refactoring.BaseRefactoringProcessor.lambda$doRefactoring$11(BaseRefactoringProcessor.java:475)
	at com.intellij.refactoring.BaseRefactoringProcessor.lambda$doRefactoring$12(BaseRefactoringProcessor.java:486)
	at com.intellij.openapi.application.impl.ApplicationImpl.lambda$runWriteActionWithProgressInDispatchThread$15(ApplicationImpl.java:980)
	at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$runProcess$1(CoreProgressManager.java:170)
	at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:548)
	at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:493)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:94)
	at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:157)
	at com.intellij.openapi.progress.util.PotemkinProgress.runInSwingThread(PotemkinProgress.java:167)
	at com.intellij.openapi.application.impl.ApplicationImpl.runWriteActionWithProgressInDispatchThread(ApplicationImpl.java:980)
	at com.intellij.refactoring.BaseRefactoringProcessor.doRefactoring(BaseRefactoringProcessor.java:486)
	at com.intellij.refactoring.BaseRefactoringProcessor.lambda$execute$4(BaseRefactoringProcessor.java:314)
	at com.intellij.openapi.command.impl.CoreCommandProcessor.executeCommand(CoreCommandProcessor.java:149)
	at com.intellij.openapi.command.impl.CoreCommandProcessor.executeCommand(CoreCommandProcessor.java:109)
	at com.intellij.openapi.command.impl.CoreCommandProcessor.executeCommand(CoreCommandProcessor.java:99)
	at com.intellij.refactoring.BaseRefactoringProcessor.execute(BaseRefactoringProcessor.java:312)
	at com.intellij.refactoring.BaseRefactoringProcessor.doRun(BaseRefactoringProcessor.java:243)
	at com.intellij.openapi.fileEditor.impl.NonProjectFileWritingAccessProvider.disableChecksDuring(NonProjectFileWritingAccessProvider.java:181)
	at com.intellij.refactoring.BaseRefactoringProcessor.run(BaseRefactoringProcessor.java:553)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.ConvertToJavaHandler.invokeInner(ConvertToJavaHandler.java:73)
	at org.jetbrains.plugins.groovy.refactoring.convertToJava.ConvertToJavaHandler.invoke(ConvertToJavaHandler.java:42)
	at com.intellij.refactoring.actions.BaseRefactoringAction.actionPerformed(BaseRefactoringAction.java:131)
	at com.intellij.openapi.actionSystem.ex.ActionUtil$1.run(ActionUtil.java:216)
	at com.intellij.openapi.application.TransactionGuardImpl.runSyncTransaction(TransactionGuardImpl.java:86)
	at com.intellij.openapi.application.TransactionGuardImpl.submitTransactionAndWait(TransactionGuardImpl.java:151)
	at com.intellij.openapi.actionSystem.ex.ActionUtil.performActionDumbAware(ActionUtil.java:231)
	at com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.lambda$actionPerformed$0(ActionMenuItem.java:310)
	at com.intellij.openapi.wm.impl.FocusManagerImpl.runOnOwnContext(FocusManagerImpl.java:911)
	at com.intellij.openapi.wm.impl.IdeFocusManagerImpl.runOnOwnContext(IdeFocusManagerImpl.java:136)
	at com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.actionPerformed(ActionMenuItem.java:300)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
	at com.intellij.openapi.actionSystem.impl.ActionMenuItem.lambda$fireActionPerformed$0(ActionMenuItem.java:117)
	at com.intellij.openapi.application.TransactionGuardImpl.runSyncTransaction(TransactionGuardImpl.java:86)
	at com.intellij.openapi.application.TransactionGuardImpl.lambda$submitTransaction$1(TransactionGuardImpl.java:109)
	at com.intellij.openapi.application.TransactionGuardImpl.submitTransaction(TransactionGuardImpl.java:118)
	at com.intellij.openapi.application.TransactionGuard.submitTransaction(TransactionGuard.java:122)
	at com.intellij.openapi.actionSystem.impl.ActionMenuItem.fireActionPerformed(ActionMenuItem.java:117)
	at com.intellij.ui.plaf.beg.BegMenuItemUI.doClick(BegMenuItemUI.java:513)
	at com.intellij.ui.plaf.beg.BegMenuItemUI.access$300(BegMenuItemUI.java:45)
	at com.intellij.ui.plaf.beg.BegMenuItemUI$MyMouseInputHandler.mouseReleased(BegMenuItemUI.java:533)
	at java.awt.Component.processMouseEvent(Component.java:6533)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
	at java.awt.Component.processEvent(Component.java:6298)
	at java.awt.Container.processEvent(Container.java:2236)
	at java.awt.Component.dispatchEventImpl(Component.java:4889)
	at java.awt.Container.dispatchEventImpl(Container.java:2294)
	at java.awt.Component.dispatchEvent(Component.java:4711)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
	at java.awt.Container.dispatchEventImpl(Container.java:2280)
	at java.awt.Window.dispatchEventImpl(Window.java:2746)
	at java.awt.Component.dispatchEvent(Component.java:4711)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
	at java.awt.EventQueue$4.run(EventQueue.java:731)
	at java.awt.EventQueue$4.run(EventQueue.java:729)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:821)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:645)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:365)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
```

WTF!? なんじゃこりゃ
このスタックトレースの上から2行目の

```
at org.jetbrains.plugins.groovy.refactoring.convertToJava.TypeWriter.visitDisjunctionType(TypeWriter.java:155)
```
を調査することに

# 調査
## `visitDisjunctionType`
`visitDisjunctionType`って何? と検索すると、こんな[モノ](https://github.com/JetBrains/intellij-community/blob/303edac/java/java-psi-api/src/com/intellij/psi/PsiTypeVisitor.java#L62)が。

```java
  @Override
  public Object visitDisjunctionType(@NotNull PsiDisjunctionType disjunctionType) {
    //it is not available in groovy source code
    throw new UnsupportedOperationException();
  }
```

そらエラーになるわ。
どうやら引数の`PsiDisjunctionType`は`A | B`のような指定を表すらしい。

## 他にダメなのは?
`PsiType`が出てくるモノらしいがよく分からん。

# 結論
適当に変えたら動いた。
なんか変換できないなーと思ったら`A | B`を探そう。
`catch`句の型の指定部分にあるかも。(というか他にあるのかな...?)