Forbid "introduce backing property" for expect classes #KT-28382 Fixed

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

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.descriptors.impl.SyntheticFieldDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.getResolutionFacade
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToCall
 import org.jetbrains.kotlin.idea.util.hasJvmFieldAnnotation
+import org.jetbrains.kotlin.idea.util.isExpectDeclaration
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
@@ -48,7 +49,8 @@ class IntroduceBackingPropertyIntention : SelfTargetingIntention<KtProperty>(KtP
             if (bindingContext.get(BindingContext.BACKING_FIELD_REQUIRED, descriptor) == false) return false
 
             val containingClass = property.getStrictParentOfType<KtClassOrObject>() ?: return false
-            return containingClass.declarations.none { it is KtProperty && it.name == "_" + name }
+            if (containingClass.isExpectDeclaration()) return false
+            return containingClass.declarations.none { it is KtProperty && it.name == "_$name" }
         }
 
         fun introduceBackingProperty(property: KtProperty) {

idea/testData/intentions/introduceBackingProperty/expectClass.kt

@@ -0,0 +1,8 @@
+// IS_APPLICABLE: false
+// ERROR: The feature "multi platform projects" is experimental and should be enabled explicitly
+
+expect class Outer {
+    class Nested {
+        val <caret>x: Int
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -9299,6 +9299,11 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/introduceBackingProperty/const.kt");
         }
 
+        @TestMetadata("expectClass.kt")
+        public void testExpectClass() throws Exception {
+            runTest("idea/testData/intentions/introduceBackingProperty/expectClass.kt");
+        }
+
         @TestMetadata("inapplicableAbstractProperty.kt")
         public void testInapplicableAbstractProperty() throws Exception {
             runTest("idea/testData/intentions/introduceBackingProperty/inapplicableAbstractProperty.kt");