Don't remove else block if it participate in other expression (KT-18309)

#KT-18309 Fixed

idea/src/org/jetbrains/kotlin/idea/joinLines/JoinBlockIntoSingleStatementHandler.kt

@@ -42,17 +42,28 @@ class JoinBlockIntoSingleStatementHandler : JoinRawLinesHandlerDelegate {
 
         // handle nested if's
         val pparent = parent.parent
-        if (pparent is KtIfExpression && block == pparent.then && statement is KtIfExpression && statement.`else` == null) {
-            // if outer if has else-branch and inner does not have it, do not remove braces otherwise else-branch will belong to different if!
-            if (pparent.`else` != null) return -1
+        if (pparent is KtIfExpression) {
+            if (block == pparent.then && statement is KtIfExpression && statement.`else` == null) {
+                // if outer if has else-branch and inner does not have it, do not remove braces otherwise else-branch will belong to different if!
+                if (pparent.`else` != null) return -1
 
-            return MergeIfsIntention.applyTo(pparent)
+                return MergeIfsIntention.applyTo(pparent)
+            }
+
+            if (block == pparent.`else`) {
+                val ifParent = pparent.parent
+                if (!(
+                        ifParent is KtBlockExpression ||
+                        ifParent is KtDeclaration ||
+                        KtPsiUtil.isAssignment(ifParent))) {
+                    return -1
+                }
+            }
         }
 
         val newStatement = block.replace(statement)
         return newStatement.textRange!!.startOffset
     }
 
-    override fun tryJoinLines(document: Document, file: PsiFile, start: Int, end: Int)
-            = - 1
+    override fun tryJoinLines(document: Document, file: PsiFile, start: Int, end: Int) = -1
 }

idea/testData/joinLines/removeBraces/IfWithElseBlockInAssignment.kt

@@ -0,0 +1,8 @@
+fun test() {
+    val t = 1
+    val f = 2
+    val a: Int
+    a = if (true) t else {<caret>
+        f
+    }
+}

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

@@ -0,0 +1,6 @@
+fun test() {
+    val t = 1
+    val f = 2
+    val a: Int
+    a = if (true) t else <caret>f
+}

idea/testData/joinLines/removeBraces/IfWithPostfixAfterElseBlock.kt

@@ -0,0 +1,8 @@
+fun test() {
+    val t = 1
+    val f = 2
+    val a: Int
+    a = if (true) t else {<caret>
+                           f
+    }!!
+}

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

@@ -0,0 +1,7 @@
+fun test() {
+    val t = 1
+    val f = 2
+    val a: Int
+    a = if (true) t else {<caret> f
+    }!!
+}

idea/testData/joinLines/removeBraces/IfWithQualifiedAfterElseBlock.kt

@@ -0,0 +1,6 @@
+fun test() {
+    if (smth) list1 else {<caret>
+        list2
+    }.add(newItem)
+}
+

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

@@ -0,0 +1,5 @@
+fun test() {
+    if (smth) list1 else {<caret> list2
+    }.add(newItem)
+}
+

idea/tests/org/jetbrains/kotlin/idea/intentions/declarations/AbstractJoinLinesTest.java

@@ -19,15 +19,25 @@ package org.jetbrains.kotlin.idea.intentions.declarations;
 import com.intellij.codeInsight.editorActions.JoinLinesHandler;
 import com.intellij.openapi.projectRoots.JavaSdk;
 import com.intellij.openapi.projectRoots.Sdk;
+import com.intellij.rt.execution.junit.FileComparisonFailure;
 import com.intellij.testFramework.LightCodeInsightTestCase;
 import org.apache.commons.lang.SystemUtils;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.kotlin.test.KotlinTestUtils;
+
+import java.io.File;
 
 public abstract class AbstractJoinLinesTest extends LightCodeInsightTestCase {
     public void doTest(@NotNull String path) throws Exception {
         configureByFile(path);
         new JoinLinesHandler(null).execute(getEditor(), getCurrentEditorDataContext());
-        checkResultByFile(path + ".after");
+        String afterFilePath = path + ".after";
+        try {
+            checkResultByFile(afterFilePath);
+        }
+        catch (FileComparisonFailure e) {
+            KotlinTestUtils.assertEqualsToFile(new File(afterFilePath), getEditor());
+        }
     }
 
     @NotNull

idea/tests/org/jetbrains/kotlin/idea/intentions/declarations/JoinLinesTestGenerated.java

@@ -260,6 +260,24 @@ public class JoinLinesTestGenerated extends AbstractJoinLinesTest {
             doTest(fileName);
         }
 
+        @TestMetadata("IfWithElseBlockInAssignment.kt")
+        public void testIfWithElseBlockInAssignment() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/joinLines/removeBraces/IfWithElseBlockInAssignment.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("IfWithPostfixAfterElseBlock.kt")
+        public void testIfWithPostfixAfterElseBlock() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/joinLines/removeBraces/IfWithPostfixAfterElseBlock.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("IfWithQualifiedAfterElseBlock.kt")
+        public void testIfWithQualifiedAfterElseBlock() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/joinLines/removeBraces/IfWithQualifiedAfterElseBlock.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("LambdaBody.kt")
         public void testLambdaBody() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/joinLines/removeBraces/LambdaBody.kt");