Extraction Engine: Generate function/property accessor with expression body (whenever applicable)

#KT-6405 Fixed

compiler/frontend/src/org/jetbrains/kotlin/psi/JetPsiFactory.kt

@@ -630,6 +630,15 @@ public class JetPsiFactory(private val project: Project) {
             return this
         }
 
+        public fun expressionBody(body: String): CallableBuilder {
+            assert(state == State.BODY || state == State.TYPE_CONSTRAINTS)
+
+            sb.append(bodyPrefix()).append(" = ").append(body)
+            state = State.DONE
+
+            return this
+        }
+
         public fun initializer(body: String): CallableBuilder {
             assert(target == Target.READ_ONLY_PROPERTY && (state == State.BODY || state == State.TYPE_CONSTRAINTS))
 

idea/src/org/jetbrains/kotlin/idea/debugger/evaluate/extractFunctionForDebuggerUtil.kt

@@ -101,11 +101,11 @@ fun getFunctionForExtractedFragment(
             throw EvaluateExceptionUtil.createEvaluateException("Following declarations are unavailable in debug scope: ${validationResult.conflicts.keySet().map { it.getText() }.joinToString(",")}")
         }
 
-        val config = ExtractionGeneratorConfiguration(
-                validationResult.descriptor,
-                ExtractionGeneratorOptions(inTempFile = true, flexibleTypesAllowed = true, allowDummyName = true)
-        )
-        return config.generateDeclaration()
+        val generatorOptions = ExtractionGeneratorOptions(inTempFile = true,
+                                                          flexibleTypesAllowed = true,
+                                                          allowDummyName = true,
+                                                          allowExpressionBody = false)
+        return ExtractionGeneratorConfiguration(validationResult.descriptor, generatorOptions).generateDeclaration()
     }
 
     return runReadAction { generateFunction() }

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertToExpressionBodyAction.kt

@@ -32,13 +32,17 @@ import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 public class ConvertToExpressionBodyAction : PsiElementBaseIntentionAction() {
     override fun getFamilyName(): String = JetBundle.message("convert.to.expression.body.action.family.name")
 
-    override fun isAvailable(project: Project, editor: Editor, element: PsiElement): Boolean {
-        setText(JetBundle.message("convert.to.expression.body.action.name"))
+    public fun isAvailable(element: PsiElement): Boolean {
         val data = calcData(element)
         return data != null && !containsReturn(data.value)
     }
 
-    override fun invoke(project: Project, editor: Editor, element: PsiElement) {
+    override fun isAvailable(project: Project, editor: Editor, element: PsiElement): Boolean {
+        setText(JetBundle.message("convert.to.expression.body.action.name"))
+        return isAvailable(element)
+    }
+
+    public fun invoke(element: PsiElement, editor: Editor? = null) {
         val (declaration, value) = calcData(element)!!
 
         if (!declaration.hasDeclaredReturnType() && declaration is JetNamedFunction) {
@@ -55,12 +59,21 @@ public class ConvertToExpressionBodyAction : PsiElementBaseIntentionAction() {
         if (declaration.hasDeclaredReturnType() && declaration is JetCallableDeclaration && canOmitType(declaration)) {
             val typeRef = declaration.getTypeReference()!!
             val colon = declaration.getColon()!!
-            val range = TextRange(colon.getTextRange().getStartOffset(), typeRef.getTextRange().getEndOffset())
-            editor.getSelectionModel().setSelection(range.getStartOffset(), range.getEndOffset())
-            editor.getCaretModel().moveToOffset(range.getEndOffset())
+            if (editor != null) {
+                val range = TextRange(colon.getTextRange().getStartOffset(), typeRef.getTextRange().getEndOffset())
+                editor.getSelectionModel().setSelection(range.getStartOffset(), range.getEndOffset())
+                editor.getCaretModel().moveToOffset(range.getEndOffset())
+            }
+            else {
+                (declaration : PsiElement).deleteChildRange(colon, typeRef)
+            }
         }
     }
 
+    override fun invoke(project: Project, editor: Editor, element: PsiElement) {
+        invoke(element, editor)
+    }
+
     private fun canOmitType(declaration: JetCallableDeclaration): Boolean {
         if (declaration.getModifierList()?.hasModifier(JetTokens.OVERRIDE_KEYWORD) ?: false) return true
         val descriptor = declaration.resolveToDescriptor()

idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractionEngine/ExtractableCodeDescriptor.kt

@@ -364,7 +364,8 @@ data class ExtractionGeneratorOptions(
         val inTempFile: Boolean = false,
         val target: ExtractionTarget = ExtractionTarget.FUNCTION,
         val flexibleTypesAllowed: Boolean = false,
-        val allowDummyName: Boolean = false
+        val allowDummyName: Boolean = false,
+        val allowExpressionBody: Boolean = true
 ) {
     default object {
         val DEFAULT = ExtractionGeneratorOptions()

idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractionEngine/extractableAnalysisUtil.kt

@@ -72,6 +72,7 @@ import org.jetbrains.kotlin.resolve.calls.callUtil.*
 import org.jetbrains.kotlin.diagnostics.*
 import java.util.logging.*
 import com.intellij.openapi.diagnostic.Logger
+import org.jetbrains.kotlin.idea.caches.resolve.analyzeFully
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfTypeAndBranch
 
 private val DEFAULT_RETURN_TYPE = KotlinBuiltIns.getInstance().getUnitType()
@@ -881,11 +882,14 @@ fun ExtractableCodeDescriptor.validate(): ExtractableCodeDescriptorWithConflicts
 
     val conflicts = MultiMap<PsiElement, String>()
 
-    val result = ExtractionGeneratorConfiguration(this, ExtractionGeneratorOptions(inTempFile = true)).generateDeclaration()
+    val result = ExtractionGeneratorConfiguration(
+            this,
+            ExtractionGeneratorOptions(inTempFile = true, allowExpressionBody = false)
+    ).generateDeclaration()
 
     val valueParameterList = (result.declaration as? JetNamedFunction)?.getValueParameterList()
     val body = result.declaration.getGeneratedBody()
-    val bindingContext = body.analyze()
+    val bindingContext = body.analyzeFully()
 
     fun validateBody() {
         for ((originalOffset, resolveResult) in extractionData.refOffsetToDeclaration) {

idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractionEngine/extractorUtil.kt

@@ -17,32 +17,17 @@
 package org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine
 
 import com.intellij.psi.PsiElement
-import org.jetbrains.kotlin.psi.JetDeclaration
-import org.jetbrains.kotlin.psi.JetProperty
-import org.jetbrains.kotlin.psi.JetPsiFactory.CallableBuilder
-import org.jetbrains.kotlin.psi.JetNamedDeclaration
-import org.jetbrains.kotlin.psi.JetPsiFactory
-import java.util.LinkedHashMap
-import java.util.Collections
-import org.jetbrains.kotlin.psi.psiUtil.isFunctionLiteralOutsideParentheses
-import org.jetbrains.kotlin.psi.JetFunctionLiteralArgument
-import org.jetbrains.kotlin.idea.util.psiModificationUtil.moveInsideParenthesesAndReplaceWith
-import org.jetbrains.kotlin.psi.psiUtil.appendElement
-import org.jetbrains.kotlin.psi.psiUtil.replaced
-import org.jetbrains.kotlin.psi.JetBlockExpression
-import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.ParameterUpdate
-import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.Jump
-import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.Initializer
-import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.ExpressionValue
-import org.jetbrains.kotlin.psi.JetReturnExpression
-import org.jetbrains.kotlin.idea.refactoring.JetNameValidatorImpl
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.idea.intentions.ConvertToExpressionBodyAction
 import org.jetbrains.kotlin.idea.refactoring.JetNameSuggester
 import org.jetbrains.kotlin.idea.refactoring.JetNameValidatorImpl
-import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.*
-import org.jetbrains.kotlin.idea.util.IdeDescriptorRenderers
-import org.jetbrains.kotlin.idea.refactoring.isMultiLine
+import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.ExpressionValue
+import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.Initializer
+import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.Jump
+import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValue.ParameterUpdate
 import org.jetbrains.kotlin.idea.refactoring.introduce.extractionEngine.OutputValueBoxer.AsTuple
+import org.jetbrains.kotlin.idea.refactoring.isMultiLine
+import org.jetbrains.kotlin.idea.util.IdeDescriptorRenderers
 import org.jetbrains.kotlin.idea.util.ShortenReferences
 import org.jetbrains.kotlin.idea.util.psi.patternMatching.JetPsiRange
 import org.jetbrains.kotlin.idea.util.psi.patternMatching.JetPsiRange.Match
@@ -53,7 +38,6 @@ import org.jetbrains.kotlin.idea.util.psi.patternMatching.UnifierParameter
 import org.jetbrains.kotlin.idea.util.psiModificationUtil.moveInsideParenthesesAndReplaceWith
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.JetPsiFactory.CallableBuilder
-import org.jetbrains.kotlin.psi.JetPsiFactory.CallableBuilder.Target
 import org.jetbrains.kotlin.psi.codeFragmentUtil.DEBUG_TYPE_REFERENCE_STRING
 import org.jetbrains.kotlin.psi.codeFragmentUtil.debugTypeInfo
 import org.jetbrains.kotlin.psi.codeFragmentUtil.suppressDiagnosticsInDebugMode
@@ -526,6 +510,14 @@ fun ExtractionGeneratorConfiguration.generateDeclaration(
             !defaultValue.callSiteReturn ->
                 replaceWithReturn(lastExpression!!, returnExpression, expressionToUnifyWith)
         }
+
+        if (generatorOptions.allowExpressionBody) {
+            val convertToExpressionBody = ConvertToExpressionBodyAction()
+            val bodyExpression = body.getStatements().singleOrNull()
+            if (bodyExpression != null && !bodyExpression.isMultiLine() && convertToExpressionBody.isAvailable(body)) {
+                convertToExpressionBody.invoke(body)
+            }
+        }
     }
 
     fun insertDeclaration(declaration: JetNamedDeclaration, anchor: PsiElement): JetNamedDeclaration {

idea/testData/refactoring/extractFunction/basic/localExtraction.kt.after

@@ -1,8 +1,6 @@
 fun foo(a: Int): Int {
     // SIBLING:
-    fun i(): Int {
-        return a + 10
-    }
+    fun i() = a + 10
 
     return i()
 }

idea/testData/refactoring/extractFunction/basic/noConflictWithInnerFunction.kt.after

@@ -1,9 +1,7 @@
 fun foo() {
     val a = 1
     // SIBLING:
-    fun b1(): Boolean {
-        return a > 0
-    }
+    fun b1() = a > 0
 
     if (b1()) {
         fun b(): Int { return 0 }

idea/testData/refactoring/extractFunction/basic/traitFunction.kt.after

@@ -3,7 +3,5 @@ trait T{
         return i()
     }
 
-    fun i(): Int {
-        return 1
-    }
+    fun i() = 1
 }

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalExprInIfCondition.kt.after

@@ -8,6 +8,4 @@ fun foo(a: Int): Int {
     return if (b(a, b)) 1 else if (a - b < 0) 2 else b
 }
 
-private fun b(a: Int, b: Int): Boolean {
-    return a + b > 0
-}
+private fun b(a: Int, b: Int) = a + b > 0

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalExprInIfElse.kt.after

@@ -8,6 +8,4 @@ fun foo(a: Int): Int {
     return if (a + b > 0) 1 else i(a, b)
 }
 
-private fun i(a: Int, b: Int): Int {
-    return if (a - b < 0) 2 else b
-}
+private fun i(a: Int, b: Int) = if (a - b < 0) 2 else b

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalExprInIfThen.kt.after

@@ -4,6 +4,4 @@ fun foo(a: Int): Int {
     return if (a + b > 0) i() else if (a - b < 0) 2 else b
 }
 
-private fun i(): Int {
-    return 1
-}
+private fun i() = 1

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalExprInWhenBranch.kt.after

@@ -10,6 +10,4 @@ fun foo(a: Int): Int {
     }
 }
 
-private fun i(b: Int): Int {
-    return b
-}
+private fun i(b: Int) = b

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalExprInWhenCondition.kt.after

@@ -8,6 +8,4 @@ fun foo(a: Int): Int {
     }
 }
 
-private fun i(): Int {
-    return 0
-}
+private fun i() = 0

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalExprInWhenSubject.kt.after

@@ -12,6 +12,4 @@ fun foo(a: Int): Int {
     }
 }
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalExpressionBodyFunction.kt.after

@@ -5,6 +5,4 @@
 // SIBLING:
 fun foo(a: Int, b: Int): Int = i(a, b)
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/evalIfExpr.kt.after

@@ -8,6 +8,4 @@ fun foo(a: Int): Int {
     return i(a, b) 
 }
 
-private fun i(a: Int, b: Int): Int {
-    return if (a + b > 0) 1 else if (a - b < 0) 2 else b
-}
+private fun i(a: Int, b: Int) = if (a + b > 0) 1 else if (a - b < 0) 2 else b

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/simpleEvalExpr.kt.after

@@ -8,6 +8,4 @@ fun foo(a: Int): Int {
     return i(a, b)
 }
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/trailingLambdaEmptyArgList.kt.after

@@ -5,6 +5,4 @@ fun foo(t: Array<Int>) {
     t.check(function())
 }
 
-private fun function(): (Int) -> Boolean {
-    return { it + 1 > 1 }
-}
+private fun function() = { it + 1 > 1 }

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/trailingLambdaNoArgList.kt.after

@@ -5,6 +5,4 @@ fun foo(t: Array<Int>) {
     t.check(function())
 }
 
-private fun function(): (Int) -> Boolean {
-    return { it + 1 > 1 }
-}
+private fun function() = { it + 1 > 1 }

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/trailingLambdaNonEmptyArgList.kt.after

@@ -5,6 +5,4 @@ fun foo(t: Array<Int>) {
     t.check(1, 2, function())
 }
 
-private fun function(): (Int) -> Boolean {
-    return { it + 1 > 1 }
-}
+private fun function() = { it + 1 > 1 }

idea/testData/refactoring/extractFunction/controlFlow/evaluateExpression/trailingLambdaNonEmptyArgListWithNamedArgs.kt.after

@@ -5,6 +5,4 @@ fun foo(t: Array<Int>) {
     t.check(a = 1, b = 2, f = function())
 }
 
-private fun function(): (Int) -> Boolean {
-    return { it + 1 > 1 }
-}
+private fun function() = { it + 1 > 1 }

idea/testData/refactoring/extractFunction/controlFlow/throws/evalExpressionWithThrow.kt.after

@@ -11,6 +11,4 @@ fun foo(a: Int): Int {
     return t
 }
 
-private fun i(a: Int, b: Int): Int {
-    return if (a > 0) throw Exception("") else a + b
-}
+private fun i(a: Int, b: Int) = if (a > 0) throw Exception("") else a + b

idea/testData/refactoring/extractFunction/defaultContainer/anonymousObject.kt.after

@@ -5,9 +5,7 @@ class A {
                 return i()
             }
 
-            private fun i(): Int {
-                return a + b - 1
-            }
+            private fun i() = a + b - 1
         }
     }
 }

idea/testData/refactoring/extractFunction/defaultContainer/classFunction.kt.after

@@ -8,8 +8,6 @@ class A {
             return i(a, b)
         }
 
-        private fun i(a: Int, b: Int): Int {
-            return a + b - 1
-        }
+        private fun i(a: Int, b: Int) = a + b - 1
     }
 }

idea/testData/refactoring/extractFunction/defaultContainer/lambda.kt.after

@@ -9,7 +9,5 @@ class A {
         }.invoke()
     }
 
-    private fun i(a: Int, b: Int): Int {
-        return a + b - 1
-    }
+    private fun i(a: Int, b: Int) = a + b - 1
 }

idea/testData/refactoring/extractFunction/defaultContainer/localClass.kt.after

@@ -5,9 +5,7 @@ class A {
                 return i()
             }
 
-            private fun i(): Int {
-                return a + b - 1
-            }
+            private fun i() = a + b - 1
         }
 
         return L().invoke()

idea/testData/refactoring/extractFunction/defaultContainer/localFunction.kt.after

@@ -1,7 +1,5 @@
 fun foo(a: Int, b: Int): Int {
-    fun i(): Int {
-        return a + b - 1
-    }
+    fun i() = a + b - 1
 
     fun bar() {
         return i()

idea/testData/refactoring/extractFunction/defaultContainer/nestedLambda.kt.after

@@ -9,7 +9,5 @@ class A {
         }.invoke()
     }
 
-    private fun i(a: Int, b: Int): Int {
-        return a + b - 1
-    }
+    private fun i(a: Int, b: Int) = a + b - 1
 }

idea/testData/refactoring/extractFunction/defaultContainer/topLevelFunction.kt.after

@@ -6,6 +6,4 @@ fun foo(a: Int, b: Int): Int {
     return i(a, b)
 }
 
-private fun i(a: Int, b: Int): Int {
-    return a + b - 1
-}
+private fun i(a: Int, b: Int) = a + b - 1

idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt.after

@@ -8,6 +8,4 @@ class A(a: Int, b: Int): T
 
 class B(a: Int, b: Int): T by A(i(a, b), a - b)
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt.after

@@ -6,6 +6,4 @@ class A(a: Int, b: Int): T
 
 class B(t: T): T by t(t)
 
-private fun t(t: T): T {
-    return t
-}
+private fun t(t: T) = t

idea/testData/refactoring/extractFunction/delegation/delegationBySuperCall.kt.after

@@ -6,6 +6,4 @@ open class A(a: Int, b: Int)
 
 class B(a: Int, b: Int): A(i(a, b), a - b)
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/duplicates/insertAfterDuplicates.kt.after

@@ -3,7 +3,5 @@ class A {
     val x = i()
     val y = i()
 
-    private fun i(): Int {
-        return 1 + 1
-    }
+    private fun i() = 1 + 1
 }

idea/testData/refactoring/extractFunction/duplicates/insertBeforeDuplicates.kt.after

@@ -4,6 +4,4 @@ fun foo() {
     val y = i()
 }
 
-private fun i(): Int {
-    return 1 + 1
-}
+private fun i() = 1 + 1

idea/testData/refactoring/extractFunction/duplicates/nestedStrongMatch.kt.after

@@ -5,6 +5,4 @@ fun main(args: Array<String>) {
     val y = i()
 }
 
-private fun i(): Int {
-    return 1 + 1
-}
+private fun i() = 1 + 1

idea/testData/refactoring/extractFunction/duplicates/notNullAssertion.kt.after

@@ -11,6 +11,4 @@ fun foo(): Int {
     }
 }
 
-private fun i(s: String?): Int {
-    return s!!.length
-}
+private fun i(s: String?) = s!!.length

idea/testData/refactoring/extractFunction/duplicates/singleExpression.kt.after

@@ -24,6 +24,4 @@ fun bar() {
     i(f(), f())
 }
 
-private fun i(a: Int, b: Int): Int {
-    return a + b * a
-}
+private fun i(a: Int, b: Int) = a + b * a

idea/testData/refactoring/extractFunction/initializers/accessors/memberProperty.kt.after

@@ -1,7 +1,5 @@
 class A(val a: Int, val b: Int) {
     val foo: Int get() = i() - 1
 
-    private fun i(): Int {
-        return a + b
-    }
+    private fun i() = a + b
 }

idea/testData/refactoring/extractFunction/initializers/accessors/memberPropertyWithLambda.kt.after

@@ -1,7 +1,5 @@
 class A(val a: Int, val b: Int) {
     val foo: Int get() = { i() - 1 }.invoke()
 
-    private fun i(): Int {
-        return a + b
-    }
+    private fun i() = a + b
 }

idea/testData/refactoring/extractFunction/initializers/accessors/topLevelProperty.kt.after

@@ -2,6 +2,4 @@ val a = 1
 val b = 1
 val foo: Int get() = i() - 1
 
-private fun i(): Int {
-    return a + b
-}
+private fun i() = a + b

idea/testData/refactoring/extractFunction/initializers/accessors/topLevelPropertyWithLambda.kt.after

@@ -2,6 +2,4 @@ val a = 1
 val b = 1
 val foo: Int get() = { i() - 1 }.invoke()
 
-private fun i(): Int {
-    return a + b
-}
+private fun i() = a + b

idea/testData/refactoring/extractFunction/initializers/classes/classInitializer.kt.after

@@ -5,7 +5,5 @@ class A(val a: Int, b: Int) {
         println(i(b) - 1)
     }
 
-    private fun i(b: Int): Int {
-        return a + b
-    }
+    private fun i(b: Int) = a + b
 }

idea/testData/refactoring/extractFunction/initializers/classes/classInitializerWithLambda.kt.after

@@ -5,7 +5,5 @@ class A(val a: Int, b: Int) {
         println({ i(b) - 1 }.invoke())
     }
 
-    private fun i(b: Int): Int {
-        return a + b
-    }
+    private fun i(b: Int) = a + b
 }

idea/testData/refactoring/extractFunction/initializers/classes/classParameters.kt.after

@@ -3,6 +3,4 @@
 val n = 1
 class A(val a: Int, val b: Int = i(a))
 
-private fun i(a: Int): Int {
-    return a + n
-}
+private fun i(a: Int) = a + n

idea/testData/refactoring/extractFunction/initializers/classes/classParametersWithLambda.kt.after

@@ -3,6 +3,4 @@
 val n = 1
 class A(val a: Int, val b: Int = { i(a) }.invoke())
 
-private fun i(a: Int): Int {
-    return a + n
-}
+private fun i(a: Int) = a + n

idea/testData/refactoring/extractFunction/initializers/functions/localFunction.kt.after

@@ -3,9 +3,7 @@
 // PARAM_DESCRIPTOR: value-parameter val a: kotlin.Int defined in bar.foo
 // PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in bar.foo
 fun bar(n: Int) {
-    fun i(a: Int, b: Int): Int {
-        return a + b - n
-    }
+    fun i(a: Int, b: Int) = a + b - n
 
     fun foo(a: Int, b: Int) = i(a, b) - 1
 }

idea/testData/refactoring/extractFunction/initializers/functions/localFunctionWithLambda.kt.after

@@ -3,9 +3,7 @@
 // PARAM_DESCRIPTOR: value-parameter val a: kotlin.Int defined in bar.foo
 // PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in bar.foo
 fun bar(n: Int) {
-    fun i(a: Int, b: Int): Int {
-        return a + b - n
-    }
+    fun i(a: Int, b: Int) = a + b - n
 
     fun foo(a: Int, b: Int) = { i(a, b) - 1 }.invoke()
 }

idea/testData/refactoring/extractFunction/initializers/functions/memberFunction.kt.after

@@ -5,7 +5,5 @@
 class A(val n: Int) {
     fun foo(a: Int, b: Int) = i(a, b) - 1
 
-    private fun i(a: Int, b: Int): Int {
-        return a + b - n
-    }
+    private fun i(a: Int, b: Int) = a + b - n
 }

idea/testData/refactoring/extractFunction/initializers/functions/memberFunctionParameters.kt.after

@@ -3,7 +3,5 @@
 class A(val n: Int) {
     fun foo(a: Int, b: Int = i(a)) = a + b - n - 1
 
-    private fun i(a: Int): Int {
-        return a + n
-    }
+    private fun i(a: Int) = a + n
 }

idea/testData/refactoring/extractFunction/initializers/functions/memberFunctionParametersWithLambda.kt.after

@@ -3,7 +3,5 @@
 class A(val n: Int) {
     fun foo(a: Int, b: Int = { i(a) }.invoke()) = a + b - n - 1
 
-    private fun i(a: Int): Int {
-        return a + n
-    }
+    private fun i(a: Int) = a + n
 }

idea/testData/refactoring/extractFunction/initializers/functions/memberFunctionWithLambda.kt.after

@@ -5,7 +5,5 @@
 class A(val n: Int) {
     fun foo(a: Int, b: Int) = { i(a, b) - 1 }.invoke()
 
-    private fun i(a: Int, b: Int): Int {
-        return a + b - n
-    }
+    private fun i(a: Int, b: Int) = a + b - n
 }

idea/testData/refactoring/extractFunction/initializers/functions/topLevelFunction.kt.after

@@ -4,6 +4,4 @@
 // PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in foo
 fun foo(a: Int, b: Int) = i(a, b) - 1
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/initializers/functions/topLevelFunctionParameters.kt.after

@@ -3,6 +3,4 @@
 val n = 1
 fun foo(a: Int, b: Int = i(a)) = a + b - 1
 
-private fun i(a: Int): Int {
-    return a + n
-}
+private fun i(a: Int) = a + n

idea/testData/refactoring/extractFunction/initializers/functions/topLevelFunctionParametersWithLambda.kt.after

@@ -3,6 +3,4 @@
 val n = 1
 fun foo(a: Int, b: Int = { i(a) }) = a + b - 1
 
-private fun i(a: Int): Int {
-    return a + n
-}
+private fun i(a: Int) = a + n

idea/testData/refactoring/extractFunction/initializers/functions/topLevelFunctionWithLambda.kt.after

@@ -4,6 +4,4 @@
 // PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in foo
 fun foo(a: Int, b: Int) = { i(a, b) - 1 }.invoke()
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/initializers/properties/localProperty.kt.after

@@ -6,6 +6,4 @@ fun bar(a: Int, b: Int) {
     val foo = i(a, b) - 1
 }
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/initializers/properties/localPropertyWithLambda.kt.after

@@ -6,6 +6,4 @@ fun bar(a: Int, b: Int) {
     val foo = { i(a, b) - 1 }.invoke()
 }
 
-private fun i(a: Int, b: Int): Int {
-    return a + b
-}
+private fun i(a: Int, b: Int) = a + b

idea/testData/refactoring/extractFunction/initializers/properties/memberProperty.kt.after

@@ -3,7 +3,5 @@
 class A(val a: Int, b: Int) {
     val foo = i(b) - 1
 
-    private fun i(b: Int): Int {
-        return a + b
-    }
+    private fun i(b: Int) = a + b
 }

idea/testData/refactoring/extractFunction/initializers/properties/memberPropertyWithLambda.kt.after

@@ -3,7 +3,5 @@
 class A(val a: Int, b: Int) {
     val foo = { i(b) - 1 }.invoke()
 
-    private fun i(b: Int): Int {
-        return a + b
-    }
+    private fun i(b: Int) = a + b
 }

idea/testData/refactoring/extractFunction/initializers/properties/multiDeclaration.kt.after

@@ -4,6 +4,4 @@ fun foo() {
     val (a, b) = pair()
 }
 
-private fun pair(): Pair<Int, Int> {
-    return 1 to 2
-}
+private fun pair() = 1 to 2

idea/testData/refactoring/extractFunction/initializers/properties/topLevelProperty.kt.after

@@ -2,6 +2,4 @@ val a = 1
 val b = 1
 val foo = i() - 1
 
-private fun i(): Int {
-    return a + b
-}
+private fun i() = a + b

idea/testData/refactoring/extractFunction/initializers/properties/topLevelPropertyWithLambda.kt.after

@@ -2,6 +2,4 @@ val a = 1
 val b = 1
 val foo = { i() - 1 }.invoke()
 
-private fun i(): Int {
-    return a + b
-}
+private fun i() = a + b

idea/testData/refactoring/extractFunction/parameters/candidateTypes/flexibleTypesWithNull.kt.after

@@ -7,6 +7,4 @@ fun test() {
     val n = i(property)
 }
 
-private fun i(property: String?): Int? {
-    return property?.length()
-}
+private fun i(property: String?) = property?.length()

idea/testData/refactoring/extractFunction/parameters/candidateTypes/flexibleTypesWithoutNull.kt.after

@@ -7,6 +7,4 @@ fun test() {
     val n = i(property)
 }
 
-private fun i(property: String): Int {
-    return property.length()
-}
+private fun i(property: String) = property.length()

idea/testData/refactoring/extractFunction/parameters/extractThis/explicitLabeledThisInMember.kt.after

@@ -19,6 +19,4 @@ public class A(): Z() {
     }
 }
 
-private fun i(a1: A, b1: A.B): Int {
-    return a1.a + b1.b + a1.z + b1.z
-}
+private fun i(a1: A, b1: A.B) = a1.a + b1.b + a1.z + b1.z

idea/testData/refactoring/extractFunction/parameters/extractThis/explicitThisInExtension.kt.after

@@ -7,6 +7,4 @@ fun Z.foo(): Int {
     return i() + 1
 }
 
-private fun Z.i(): Int {
-    return this.a
-}
+private fun Z.i() = this.a

idea/testData/refactoring/extractFunction/parameters/extractThis/explicitThisInMember.kt.after

@@ -19,6 +19,4 @@ public class A(): Z() {
     }
 }
 
-private fun i(a1: A, b1: A.B): Int {
-    return a1.a + b1.b + b1.z
-}
+private fun i(a1: A, b1: A.B) = a1.a + b1.b + b1.z

idea/testData/refactoring/extractFunction/parameters/extractThis/implicitAndExplicitLabeledThisInMember.kt.after

@@ -19,6 +19,4 @@ public class A(): Z() {
     }
 }
 
-private fun i(a1: A, b1: A.B): Int {
-    return a1.a + b1.b + a1.z + b1.z
-}
+private fun i(a1: A, b1: A.B) = a1.a + b1.b + a1.z + b1.z

idea/testData/refactoring/extractFunction/parameters/extractThis/implicitAndExplicitThisInExtension.kt.after

@@ -7,6 +7,4 @@ fun Z.foo(): Int {
     return i() + 1
 }
 
-private fun Z.i(): Int {
-    return this.a + a
-}
+private fun Z.i() = this.a + a

idea/testData/refactoring/extractFunction/parameters/extractThis/implicitThisInExtension.kt.after

@@ -7,6 +7,4 @@ fun Z.foo(): Int {
     return i() + 1
 }
 
-private fun Z.i(): Int {
-    return a
-}
+private fun Z.i() = a

idea/testData/refactoring/extractFunction/parameters/extractThis/implicitThisInMember.kt.after

@@ -19,6 +19,4 @@ public class A(): Z() {
     }
 }
 
-private fun i(a1: A, b1: A.B): Int {
-    return a1.a + b1.b + b1.z
-}
+private fun i(a1: A, b1: A.B) = a1.a + b1.b + b1.z

idea/testData/refactoring/extractFunction/parameters/extractThis/qualifiedThisAsArgument.kt.after

@@ -9,9 +9,7 @@ class A {
     fun B.foo() = i(this@A, this)
 }
 
-private fun i(a1: A, b: B): Int {
-    return a1.a + b.b
-}
+private fun i(a1: A, b: B) = a1.a + b.b
 
 class B {
     val b = 1

idea/testData/refactoring/extractFunction/parameters/it/innerIt.kt.after

@@ -9,6 +9,4 @@ fun foo(t: Array<Array<Int>>) {
     }
 }
 
-private fun i(it: Int): Int {
-    return it + 1
-}
+private fun i(it: Int) = it + 1

idea/testData/refactoring/extractFunction/parameters/it/lambdaWithIt.kt.after

@@ -9,6 +9,4 @@ fun foo(t: Array<Int>) {
     }
 }
 
-private fun b(t: Array<Int>): Boolean {
-    return t.check { it + 1 > 1 }
-}
+private fun b(t: Array<Int>) = t.check { it + 1 > 1 }

idea/testData/refactoring/extractFunction/parameters/it/outerIt.kt.after

@@ -9,6 +9,4 @@ fun foo(t: Array<Array<Int>>) {
     }
 }
 
-private fun b(it: Array<Int>): Boolean {
-    return it.check { it + 1 > 1 }
-}
+private fun b(it: Array<Int>) = it.check { it + 1 > 1 }

idea/testData/refactoring/extractFunction/parameters/it/simpleIt.kt.after

@@ -9,6 +9,4 @@ fun foo(t: Array<Int>) {
     }
 }
 
-private fun i(it: Int): Int {
-    return it + 1
-}
+private fun i(it: Int) = it + 1

idea/testData/refactoring/extractFunction/parameters/misc/multipleOccurrences.kt.after

@@ -9,6 +9,4 @@ fun foo(a: Int, b: Int, c: Int): Int {
     return i(a, b, c)
 }
 
-private fun i(a: Int, b: Int, c: Int): Int {
-    return (a + b * a - c) + b * c
-}
+private fun i(a: Int, b: Int, c: Int) = (a + b * a - c) + b * c

idea/testData/refactoring/extractFunction/parameters/misc/usagesInCallArgs.kt.after

@@ -13,9 +13,7 @@ public class A() {
     }
 }
 
-private fun i(a: A, t: Int, u: Int, x: Int): Int {
-    return a.bar(t - x, u + x)
-}
+private fun i(a: A, t: Int, u: Int, x: Int) = a.bar(t - x, u + x)
 
 fun foo(a: A, x: Int): Int {
     val t = 10

idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameter.kt.after

@@ -9,6 +9,4 @@ fun foo<V: Data>(v: V): Pair<Int, V> {
     return pair(v)
 }
 
-private fun <V : Data> pair(v: V): Pair<Int, V> {
-    return Pair(v.x + 10, v)
-}
+private fun <V : Data> pair(v: V) = Pair(v.x + 10, v)

idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt.after

@@ -10,6 +10,4 @@ fun foo<V: Data>(v: V): Pair<Int, V> where V: DataEx {
     return pair(v)
 }
 
-private fun <V : Data> pair(v: V): Pair<Int, V> where V : DataEx {
-    return Pair(v.x + 10, v)
-}
+private fun <V : Data> pair(v: V) where V : DataEx = Pair(v.x + 10, v)

idea/testData/refactoring/extractFunction/typeParameters/typeParamInArgument.kt.after

@@ -9,6 +9,4 @@ class A<T> {
     }
 }
 
-private fun <T> i(d: Data<T>): Int {
-    return d.t + 1
-}
+private fun <T> i(d: Data<T>) = d.t + 1

idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt.after

@@ -17,6 +17,4 @@ class A<T: Data>(val t: T) where T: DataEx {
     }
 }
 
-private fun <T : Data, U : Data, V : Data> i(a: A<T>, b: A.B<U>, v: V): Int where T : DataEx, U : DataExEx, V : DataEx {
-    return a.t.x + b.u.x + v.x
-}
+private fun <T : Data, U : Data, V : Data> i(a: A<T>, b: A.B<U>, v: V) where T : DataEx, U : DataExEx, V : DataEx = a.t.x + b.u.x + v.x

idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt.after

@@ -14,7 +14,5 @@ class A<T: Data>(val t: T) where T: DataEx {
         }
     }
 
-    private fun <U : Data, V : Data> B<U>.i(v: V): Int where U : DataExEx, V : DataEx {
-        return t.x + u.x + v.x
-    }
+    private fun <U : Data, V : Data> B<U>.i(v: V) where U : DataExEx, V : DataEx = t.x + u.x + v.x
 }

idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt.after

@@ -11,8 +11,6 @@ class A<T: Data>(val t: T) where T: DataEx {
             return i(v)
         }
 
-        private fun <V : Data> i(v: V): Int where V : DataEx {
-            return t.x + u.x + v.x
-        }
+        private fun <V : Data> i(v: V) where V : DataEx = t.x + u.x + v.x
     }
 }

idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombined1.kt.after

@@ -15,6 +15,4 @@ class A<T: Data>(val t: T) {
     }
 }
 
-private fun <T : Data, U : Data, V : Data> i(a: A<T>, b: A.B<U>, v: V): Int {
-    return a.t.x + b.u.x + v.x
-}
+private fun <T : Data, U : Data, V : Data> i(a: A<T>, b: A.B<U>, v: V) = a.t.x + b.u.x + v.x

idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombined2.kt.after

@@ -12,7 +12,5 @@ class A<T: Data>(val t: T) {
         }
     }
 
-    private fun <U : Data, V : Data> B<U>.i(v: V): Int {
-        return t.x + u.x + v.x
-    }
+    private fun <U : Data, V : Data> B<U>.i(v: V) = t.x + u.x + v.x
 }

idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombined3.kt.after

@@ -9,8 +9,6 @@ class A<T: Data>(val t: T) {
             return i(v)
         }
 
-        private fun <V : Data> i(v: V): Int {
-            return t.x + u.x + v.x
-        }
+        private fun <V : Data> i(v: V) = t.x + u.x + v.x
     }
 }

idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt.after

@@ -12,6 +12,4 @@ class A<T: Data>(val t: T) where T: DataEx {
     }
 }
 
-private fun <T : Data, V : Data> A<T>.i(v: V): Int where T : DataEx {
-    return t.x + v.x
-}
+private fun <T : Data, V : Data> A<T>.i(v: V) where T : DataEx = t.x + v.x

idea/testData/refactoring/introduceProperty/extractWithGetterToClass.kt.after

@@ -3,9 +3,7 @@ class A(val n: Int = 1) {
     val m: Int = 2
 
     private val i: Int
-        get() {
-            return m + n + 1
-        }
+        get() = m + n + 1
 
     fun foo(): Int {
         return i

idea/testData/refactoring/introduceProperty/extractWithGetterToFile.kt.after

@@ -2,9 +2,7 @@
 val n: Int = 1
 
 private val i: Int
-    get() {
-        return n + 1
-    }
+    get() = n + 1
 
 fun foo(): Int {
     return i

idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt.after

@@ -1,9 +1,7 @@
 // EXTRACTION_TARGET: property with getter
 trait T {
     val i: Int
-        get() {
-            return 1
-        }
+        get() = 1
 
     fun foo(): Int {
         return i