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

#KT-6405 Fixed

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 }