Override/Implement: Add 'actual' modifier to overrides of 'expect'

#KT-23106 Fixed

idea/idea-core/src/org/jetbrains/kotlin/idea/core/overrideImplement/OverrideMemberChooserObject.kt

@@ -24,6 +24,7 @@ import com.intellij.psi.PsiDocCommentOwner
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
 import org.jetbrains.kotlin.idea.codeInsight.DescriptorToSourceUtilsIde
 import org.jetbrains.kotlin.idea.core.TemplateKind
 import org.jetbrains.kotlin.idea.core.getFunctionBodyTextFromTemplate
@@ -32,6 +33,7 @@ import org.jetbrains.kotlin.idea.j2k.IdeaDocCommentConverter
 import org.jetbrains.kotlin.idea.kdoc.KDocElementFactory
 import org.jetbrains.kotlin.idea.util.IdeDescriptorRenderers
 import org.jetbrains.kotlin.idea.util.approximateFlexibleTypes
+import org.jetbrains.kotlin.idea.util.expectedDescriptors
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.findDocComment.findDocComment
@@ -40,6 +42,7 @@ import org.jetbrains.kotlin.psi.psiUtil.hasExpectModifier
 import org.jetbrains.kotlin.renderer.*
 import org.jetbrains.kotlin.resolve.checkers.ExperimentalUsageChecker
 import org.jetbrains.kotlin.resolve.descriptorUtil.setSingleOverridden
+import org.jetbrains.kotlin.util.findCallableMemberBySignature
 
 interface OverrideMemberChooserObject : ClassMember {
     sealed class BodyType {
@@ -118,7 +121,12 @@ fun OverrideMemberChooserObject.generateMember(targetClass: KtClassOrObject, cop
         else -> error("Unknown member to override: $descriptor")
     }
 
-    if (!targetClass.hasActualModifier()) {
+    if (targetClass.hasActualModifier()) {
+        val expectClassDescriptors = targetClass.resolveToDescriptorIfAny()?.expectedDescriptors() ?: emptyList()
+        if (expectClassDescriptors.any { (it as? ClassDescriptor)?.findCallableMemberBySignature(immediateSuper)?.isExpect == true }) {
+            newMember.addModifier(KtTokens.ACTUAL_KEYWORD)
+        }
+    } else {
         newMember.removeModifier(KtTokens.IMPL_KEYWORD)
         newMember.removeModifier(KtTokens.ACTUAL_KEYWORD)
     }

idea/testData/multiModuleQuickFix/implementAbstractExpectMemberInheritedFromInterface/header/header.kt

@@ -0,0 +1,7 @@
+interface I {
+    fun f()
+}
+
+expect class C : I {
+    override fun f()
+}

idea/testData/multiModuleQuickFix/implementAbstractExpectMemberInheritedFromInterface/header/header.kt.after

@@ -0,0 +1,7 @@
+interface I {
+    fun f()
+}
+
+expect class C : I {
+    override fun f()
+}

idea/testData/multiModuleQuickFix/implementAbstractExpectMemberInheritedFromInterface/jvm/jvm.kt

@@ -0,0 +1,4 @@
+// "Implement members" "true"
+// DISABLE-ERRORS
+
+actual class <caret>C : I

idea/testData/multiModuleQuickFix/implementAbstractExpectMemberInheritedFromInterface/jvm/jvm.kt.after

@@ -0,0 +1,8 @@
+// "Implement members" "true"
+// DISABLE-ERRORS
+
+actual class C : I {
+    actual override fun f() {
+        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixMultiModuleTestGenerated.java

@@ -184,6 +184,11 @@ public class QuickFixMultiModuleTestGenerated extends AbstractQuickFixMultiModul
         runTest("idea/testData/multiModuleQuickFix/functionTypeReceiverToParameterByImpl/");
     }
 
+    @TestMetadata("implementAbstractExpectMemberInheritedFromInterface")
+    public void testImplementAbstractExpectMemberInheritedFromInterface() throws Exception {
+        runTest("idea/testData/multiModuleQuickFix/implementAbstractExpectMemberInheritedFromInterface/");
+    }
+
     @TestMetadata("implementMembersInImplClassNonImplInheritor")
     public void testImplementMembersInImplClassNonImplInheritor() throws Exception {
         runTest("idea/testData/multiModuleQuickFix/implementMembersInImplClassNonImplInheritor/");