Introduce Variable: Do not insert unused variable references

#KT-7227 Fixed

idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/AbstractKotlinInplaceIntroducer.kt

@@ -72,9 +72,9 @@ public abstract class AbstractKotlinInplaceIntroducer<D: JetNamedDeclaration>(
             containingFile: PsiFile,
             declaration: D,
             marker: RangeMarker,
-            exprText: String
+            exprText: String?
     ): JetExpression? {
-        if (!declaration.isValid()) return null
+        if (exprText == null || !declaration.isValid()) return null
 
         return containingFile
                 .findElementAt(marker.getStartOffset())

idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/introduceVariable/KotlinIntroduceVariableHandler.java

@@ -180,8 +180,7 @@ public class KotlinIntroduceVariableHandler extends KotlinIntroduceHandlerBase {
         Pass<OccurrencesChooser.ReplaceChoice> callback = new Pass<OccurrencesChooser.ReplaceChoice>() {
             @Override
             public void pass(OccurrencesChooser.ReplaceChoice replaceChoice) {
-                boolean replaceOccurrence =
-                        container != expression.getParent() || BindingContextUtilPackage.isUsedAsExpression(expression, bindingContext);
+                boolean replaceOccurrence = shouldReplaceOccurrence(expression, bindingContext, container);
                 List<JetExpression> allReplaces;
                 if (OccurrencesChooser.ReplaceChoice.ALL == replaceChoice) {
                     if (allOccurrences.size() > 1) replaceOccurrence = true;
@@ -415,17 +414,21 @@ public class KotlinIntroduceVariableHandler extends KotlinIntroduceHandlerBase {
                         }
                     }
                 }
-                for (JetExpression replace : allReplaces) {
-                    if (replaceOccurrence && !needBraces) {
-                        replaceExpression(replace);
-                    }
-                    else if (!needBraces) {
-                        PsiElement sibling = PsiTreeUtil.skipSiblingsBackward(replace, PsiWhiteSpace.class);
-                        if (sibling == property) {
-                            replace.getParent().deleteChildRange(property.getNextSibling(), replace);
+                if (!needBraces) {
+                    for (int i = 0; i < allReplaces.size(); i++) {
+                        JetExpression replace = allReplaces.get(i);
+
+                        if (i != 0 ? replaceOccurrence : shouldReplaceOccurrence(replace, bindingContext, commonContainer)) {
+                            replaceExpression(replace);
                         }
                         else {
-                            replace.delete();
+                            PsiElement sibling = PsiTreeUtil.skipSiblingsBackward(replace, PsiWhiteSpace.class);
+                            if (sibling == property) {
+                                replace.getParent().deleteChildRange(property.getNextSibling(), replace);
+                            }
+                            else {
+                                replace.delete();
+                            }
                         }
                     }
                 }
@@ -515,6 +518,14 @@ public class KotlinIntroduceVariableHandler extends KotlinIntroduceHandlerBase {
         );
     }
 
+    private static boolean shouldReplaceOccurrence(
+            @NotNull JetExpression expression,
+            @NotNull BindingContext bindingContext,
+            @Nullable PsiElement container
+    ) {
+        return BindingContextUtilPackage.isUsedAsExpression(expression, bindingContext) || container != expression.getParent();
+    }
+
     @Nullable
     private static PsiElement getContainer(PsiElement place) {
         if (place instanceof JetBlockExpression || place instanceof JetClassBody ||

idea/testData/refactoring/introduceVariable/FewOccurrences.kt.after

@@ -1,6 +1,5 @@
 fun a() {
     val i = 1
     i
-    i
     if (true) i
 }

idea/testData/refactoring/introduceVariable/UsedAndUnusedExpressions1.kt

@@ -0,0 +1,10 @@
+class A {
+    fun test() = 1
+}
+
+fun main(args: Array<String>) {
+    val a = A()
+    <selection>a.test()</selection>
+
+    val b = a.test()
+}

idea/testData/refactoring/introduceVariable/UsedAndUnusedExpressions1.kt.after

@@ -0,0 +1,10 @@
+class A {
+    fun test() = 1
+}
+
+fun main(args: Array<String>) {
+    val a = A()
+    val i = a.test()
+
+    val b = i
+}

idea/testData/refactoring/introduceVariable/UsedAndUnusedExpressions2.kt

@@ -0,0 +1,10 @@
+class A {
+    fun test() = 1
+}
+
+fun main(args: Array<String>) {
+    val a = A()
+    a.test()
+
+    val b = <selection>a.test()</selection>
+}

idea/testData/refactoring/introduceVariable/UsedAndUnusedExpressions2.kt.after

@@ -0,0 +1,10 @@
+class A {
+    fun test() = 1
+}
+
+fun main(args: Array<String>) {
+    val a = A()
+    val i = a.test()
+
+    val b = i
+}

idea/tests/org/jetbrains/kotlin/idea/refactoring/introduce/JetExtractionTestGenerated.java

@@ -271,6 +271,18 @@ public class JetExtractionTestGenerated extends AbstractJetExtractionTest {
             doIntroduceVariableTest(fileName);
         }
 
+        @TestMetadata("UsedAndUnusedExpressions1.kt")
+        public void testUsedAndUnusedExpressions1() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/introduceVariable/UsedAndUnusedExpressions1.kt");
+            doIntroduceVariableTest(fileName);
+        }
+
+        @TestMetadata("UsedAndUnusedExpressions2.kt")
+        public void testUsedAndUnusedExpressions2() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/introduceVariable/UsedAndUnusedExpressions2.kt");
+            doIntroduceVariableTest(fileName);
+        }
+
         @TestMetadata("WhenAddBlock.kt")
         public void testWhenAddBlock() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/introduceVariable/WhenAddBlock.kt");