KT-6019 Join lines should remove code block in when entry body

#KT-6019 Fixed

idea/src/org/jetbrains/jet/plugin/joinLines/JoinBlockIntoSingleStatementHandler.kt

@@ -23,6 +23,7 @@ import org.jetbrains.jet.lang.psi.JetFile
 import org.jetbrains.jet.lexer.JetTokens
 import org.jetbrains.jet.lang.psi.JetBlockExpression
 import org.jetbrains.jet.lang.psi.JetContainerNode
+import org.jetbrains.jet.lang.psi.JetWhenEntry
 
 public class JoinBlockIntoSingleStatementHandler : JoinRawLinesHandlerDelegate {
     override fun tryJoinRawLines(document: Document, file: PsiFile, start: Int, end: Int): Int {
@@ -34,7 +35,8 @@ public class JoinBlockIntoSingleStatementHandler : JoinRawLinesHandlerDelegate {
 
         val block = brace.getParent() as? JetBlockExpression ?: return -1
         val statement = block.getStatements().singleOrNull() ?: return -1
-        if (block.getParent() !is JetContainerNode) return -1
+        val parent = block.getParent()
+        if (parent !is JetContainerNode && parent !is JetWhenEntry) return -1
         if (block.getNode().getChildren(JetTokens.COMMENTS).isNotEmpty()) return -1 // otherwise we will loose comments
 
         val newStatement = block.replace(statement)

idea/testData/joinLines/removeBraces/WhenEntry.kt

@@ -0,0 +1,7 @@
+fun foo(p: Int) {
+    when (p) {
+        1 -> {<caret>
+            println()
+        }
+    }
+}

idea/testData/joinLines/removeBraces/WhenEntry.kt.after

@@ -0,0 +1,5 @@
+fun foo(p: Int) {
+    when (p) {
+        1 -> println()
+    }
+}

idea/tests/org/jetbrains/jet/plugin/intentions/declarations/JoinLinesTestGenerated.java

@@ -234,6 +234,12 @@ public class JoinLinesTestGenerated extends AbstractJoinLinesTest {
             doTest(fileName);
         }
 
+        @TestMetadata("WhenEntry.kt")
+        public void testWhenEntry() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/joinLines/removeBraces/WhenEntry.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("While.kt")
         public void testWhile() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/joinLines/removeBraces/While.kt");