Extract function: Do not report conflicts for fake overrides/delegates of the same callable declaration

idea/src/org/jetbrains/kotlin/idea/refactoring/jetRefactoringUtil.kt

@@ -68,13 +68,14 @@ import com.intellij.psi.PsiMethod
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.CallableDescriptor
-import org.jetbrains.kotlin.resolve.OverridingUtil
-import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 import com.intellij.psi.PsiPackage
 import org.jetbrains.kotlin.idea.util.ProjectRootsUtil
 import org.jetbrains.kotlin.psi.psiUtil.parents
 import com.intellij.refactoring.util.RefactoringUIUtil
+import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
+import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor.Kind
+import org.jetbrains.kotlin.resolve.OverridingUtil
 
 fun <T: Any> PsiElement.getAndRemoveCopyableUserData(key: Key<T>): T? {
     val data = getCopyableUserData(key)
@@ -389,6 +390,17 @@ public fun comparePossiblyOverridingDescriptors(currentDescriptor: DeclarationDe
     if (compareDescriptors(currentDescriptor, originalDescriptor)) return true
     if (originalDescriptor is CallableDescriptor) {
         if (!OverridingUtil.traverseOverridenDescriptors(originalDescriptor) { !compareDescriptors(currentDescriptor, it) }) return true
+        if (originalDescriptor !is CallableMemberDescriptor || currentDescriptor !is CallableMemberDescriptor) return false
+        val kind = originalDescriptor.getKind()
+        if (kind != Kind.FAKE_OVERRIDE && kind != Kind.DELEGATION) return false
+        if (currentDescriptor.getKind() != kind) return false
+
+        val originalOverriddenDescriptors = originalDescriptor.getOverriddenDescriptors()
+        val currentOverriddenDescriptors = currentDescriptor.getOverriddenDescriptors()
+        if (originalOverriddenDescriptors.size() != currentOverriddenDescriptors.size()) return false
+        return (currentOverriddenDescriptors zip originalOverriddenDescriptors ).all {
+            comparePossiblyOverridingDescriptors(it.first, it.second)
+        }
     }
 
     return false

idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt

@@ -0,0 +1,10 @@
+// PARAM_DESCRIPTOR: val t: <no name provided> defined in foo
+// PARAM_TYPES: T
+trait T {
+    fun test() {}
+}
+
+fun foo() {
+    val t = object: T {}
+    <selection>(object: T by t {}).test()</selection>
+}

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

@@ -0,0 +1,14 @@
+// PARAM_DESCRIPTOR: val t: <no name provided> defined in foo
+// PARAM_TYPES: T
+trait T {
+    fun test() {}
+}
+
+fun foo() {
+    val t = object: T {}
+    __dummyTestFun__(t)
+}
+
+private fun __dummyTestFun__(t: T) {
+    (object : T by t {}).test()
+}

idea/testData/refactoring/extractFunction/basic/fakeOverride.kt

@@ -0,0 +1,7 @@
+trait T {
+    fun test() {}
+}
+
+fun foo() {
+    <selection>(object: T {}).test()</selection>
+}

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

@@ -0,0 +1,11 @@
+trait T {
+    fun test() {}
+}
+
+fun foo() {
+    __dummyTestFun__()
+}
+
+private fun __dummyTestFun__() {
+    (object : T {}).test()
+}

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

@@ -366,12 +366,24 @@ public class JetExtractionTestGenerated extends AbstractJetExtractionTest {
                 JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/refactoring/extractFunction/basic"), Pattern.compile("^(.+)\\.kt$"), true);
             }
 
+            @TestMetadata("delegatingFunction.kt")
+            public void testDelegatingFunction() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt");
+                doExtractFunctionTest(fileName);
+            }
+
             @TestMetadata("extensionFunForArray.kt")
             public void testExtensionFunForArray() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/basic/extensionFunForArray.kt");
                 doExtractFunctionTest(fileName);
             }
 
+            @TestMetadata("fakeOverride.kt")
+            public void testFakeOverride() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/basic/fakeOverride.kt");
+                doExtractFunctionTest(fileName);
+            }
+
             @TestMetadata("fragmentWithComment.kt")
             public void testFragmentWithComment() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("idea/testData/refactoring/extractFunction/basic/fragmentWithComment.kt");