Drop result value if it's not needed

idea/src/org/jetbrains/kotlin/idea/codeInliner/CodeInliner.kt

@@ -70,6 +70,15 @@ class CodeInliner<TCallElement : KtElement>(
 
         val commentSaver = CommentSaver(elementToBeReplaced, saveLineBreaks = true)
 
+        // if the value to be inlined is not used and has no side effects we may drop it
+        if (codeToInline.mainExpression != null
+            && elementToBeReplaced is KtExpression
+            && !elementToBeReplaced.isUsedAsExpression(bindingContext)
+            && !codeToInline.mainExpression.shouldKeepValue(usageCount = 0)
+        ) {
+            codeToInline.mainExpression = null
+        }
+
         var receiver = nameExpression.getReceiverExpression()?.marked(USER_CODE_KEY)
         var receiverType = if (receiver != null) bindingContext.getType(receiver) else null
 
@@ -111,7 +120,7 @@ class CodeInliner<TCallElement : KtElement>(
         if (elementToBeReplaced is KtExpression) {
             if (receiver != null) {
                 val thisReplaced = codeToInline.collectDescendantsOfType<KtExpression> { it[RECEIVER_VALUE_KEY] }
-                if (receiver.shouldKeepValue(thisReplaced.size)) {
+                if (receiver.shouldKeepValue(usageCount = thisReplaced.size)) {
                     codeToInline.introduceValue(receiver, receiverType, thisReplaced, elementToBeReplaced)
                 }
             }
@@ -182,7 +191,7 @@ class CodeInliner<TCallElement : KtElement>(
 
             //TODO: sometimes we need to add explicit type arguments here because we don't have expected type in the new context
 
-            if (argument.expression.shouldKeepValue(usages.size)) {
+            if (argument.expression.shouldKeepValue(usageCount = usages.size)) {
                 introduceValuesForParameters.add(IntroduceValueForParameter(parameter, argument.expression, argument.expressionType))
             }
         }

idea/testData/quickfix/deprecatedSymbolUsage/propertyToSyntheticExtension.kt

@@ -6,6 +6,6 @@ val File.prop: String
     get() = absolutePath
 
 fun foo(file: File) {
-    file.prop<caret>
+    val v = file.prop<caret>
 }
 

idea/testData/quickfix/deprecatedSymbolUsage/propertyToSyntheticExtension.kt.after

@@ -6,6 +6,6 @@ val File.prop: String
     get() = absolutePath
 
 fun foo(file: File) {
-    file.absolutePath
+    val v = file.absolutePath
 }
 

idea/testData/quickfix/deprecatedSymbolUsage/replaceCallWithArgument.kt

@@ -3,5 +3,5 @@
 fun oldFun(p: Int): Int = p
 
 fun foo() {
-    <caret>oldFun(0)
+    val v = <caret>oldFun(0)
 }

idea/testData/quickfix/deprecatedSymbolUsage/replaceCallWithArgument.kt.after

@@ -3,5 +3,5 @@
 fun oldFun(p: Int): Int = p
 
 fun foo() {
-    <caret>0
+    val v = 0
 }

idea/testData/refactoring/inline/function/expressionBody/ComplexArgumentUsedTwice.kt

@@ -3,6 +3,6 @@ fun <caret>f(p: Int) = p + p
 fun complexFun(): Int {
 }
 
-fun main(args: Array<String>) {
-    f(complexFun())
+fun g(): Int {
+    return f(complexFun())
 }

idea/testData/refactoring/inline/function/expressionBody/ComplexArgumentUsedTwice.kt.after

@@ -1,7 +1,7 @@
 fun complexFun(): Int {
 }
 
-fun main(args: Array<String>) {
+fun g(): Int {
     val p = complexFun()
-    p + p
+    return p + p
 }

idea/testData/refactoring/inline/function/returnAtEnd/AddBlockToControlStatement.kt.after

@@ -2,18 +2,15 @@ fun main(args: Array<String>) {
     if (args.size > 0) {
         println(1)
         println(2)
-        1 + 2
     }
     else {
         println(3)
         println(4)
-        3 + 4
     }
 
     for (i in 1..10) {
         println(0)
         println(1)
-        0 + 1
     }
 
     when (args.size) {

idea/testData/refactoring/inline/function/returnAtEnd/MultipleStatements.kt.after

@@ -1,5 +1,4 @@
 fun main(args: Array<String>) {
     println(3)
     println(5)
-    3 + 5
 }

idea/testData/refactoring/inline/function/returnAtEnd/UnusedComplicatedReturnValue.kt

@@ -0,0 +1,10 @@
+fun <caret>f(p: Int): Boolean {
+    println(p)
+    return g(p)
+}
+
+fun g(p: Int): Boolean = TODO()
+
+fun main(args: Array<String>) {
+    f(1)
+}

idea/testData/refactoring/inline/function/returnAtEnd/UnusedComplicatedReturnValue.kt.after

@@ -0,0 +1,6 @@
+fun g(p: Int): Boolean = TODO()
+
+fun main(args: Array<String>) {
+    println(1)
+    g(1)
+}

idea/testData/refactoring/inline/function/returnAtEnd/UnusedReturnValue.kt

@@ -0,0 +1,11 @@
+fun <caret>f(p: Int): Boolean {
+    println(p)
+    return p > 0
+}
+
+fun g(): Int = TODO()
+
+fun main(args: Array<String>) {
+    f(1)
+    f(g())
+}

idea/testData/refactoring/inline/function/returnAtEnd/UnusedReturnValue.kt.after

@@ -0,0 +1,6 @@
+fun g(): Int = TODO()
+
+fun main(args: Array<String>) {
+    println(1)
+    println(g())
+}

idea/tests/org/jetbrains/kotlin/idea/refactoring/inline/InlineTestGenerated.java

@@ -466,6 +466,18 @@ public class InlineTestGenerated extends AbstractInlineTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("UnusedComplicatedReturnValue.kt")
+            public void testUnusedComplicatedReturnValue() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/inline/function/returnAtEnd/UnusedComplicatedReturnValue.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("UnusedReturnValue.kt")
+            public void testUnusedReturnValue() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/inline/function/returnAtEnd/UnusedReturnValue.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("ValIntializer.kt")
             public void testValIntializer() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/inline/function/returnAtEnd/ValIntializer.kt");