Fix exception in ultra-light classes in case of complex mpp hierarchy

Without the introduced override, default implementation of isEquivalentTo
runs delegate computation of `another` that is illegal
for KtUltraLightClass

^KT-28912 Fixed

idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/lightClasses/KtFakeLightClass.kt

@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.idea.caches.lightClasses
 import com.intellij.ide.highlighter.JavaFileType
 import com.intellij.openapi.project.Project
 import com.intellij.psi.*
+import com.intellij.psi.impl.PsiClassImplUtil
 import com.intellij.psi.impl.light.AbstractLightClass
 import com.intellij.psi.impl.light.LightMethod
 import com.intellij.util.IncorrectOperationException
@@ -68,6 +69,8 @@ class KtFakeLightClass(override val kotlinOrigin: KtClassOrObject) :
         else
             DescriptorUtils.isDirectSubclass(thisDescriptor, baseDescriptor)
     }
+
+    override fun isEquivalentTo(another: PsiElement?): Boolean = PsiClassImplUtil.isClassEquivalentTo(this, another)
 }
 
 class KtFakeLightMethod private constructor(
@@ -122,4 +125,4 @@ private object DummyJavaPsiFactory {
     }
 
     private val DUMMY_FILE_NAME = "_Dummy_." + JavaFileType.INSTANCE.defaultExtension
-}
+}

idea/testData/navigation/implementations/multiModule/actualTypeAliasWithAnonymousSubclass/common/common.kt

@@ -0,0 +1,14 @@
+// ULTRA_LIGHT_CLASSES
+package test
+
+expect interface Closable {
+    fun <caret>close()
+}
+
+expect class MyStream : Closable {}
+
+open class MyImpl : Closable {
+    override fun close() {}
+}
+
+// REF: [testModule_Common] (in test.MyImpl).close()

idea/testData/navigation/implementations/multiModule/actualTypeAliasWithAnonymousSubclass/jvm/jvm.kt

@@ -0,0 +1,9 @@
+package test
+
+actual interface Closable {
+    fun close()
+}
+
+actual typealias MyStream = MyImpl
+
+fun foo(): Any? = object : MyStream() {}

idea/tests/org/jetbrains/kotlin/idea/navigation/AbstractKotlinNavigationMultiModuleTest.kt

@@ -13,10 +13,12 @@ import com.intellij.psi.PsiDocumentManager
 import com.intellij.psi.PsiFile
 import org.jetbrains.kotlin.idea.codeInsight.GotoSuperActionHandler
 import org.jetbrains.kotlin.idea.multiplatform.setupMppProjectFromDirStructure
+import org.jetbrains.kotlin.idea.perf.forceUsingUltraLightClassesForTest
 import org.jetbrains.kotlin.idea.stubs.AbstractMultiModuleTest
 import org.jetbrains.kotlin.idea.test.PluginTestCaseBase
 import org.jetbrains.kotlin.idea.test.extractMarkerOffset
 import org.jetbrains.kotlin.idea.test.findFileWithCaret
+import org.jetbrains.kotlin.test.InTextDirectivesUtils
 import java.io.File
 
 abstract class AbstractKotlinNavigationMultiModuleTest : AbstractMultiModuleTest() {
@@ -25,6 +27,10 @@ abstract class AbstractKotlinNavigationMultiModuleTest : AbstractMultiModuleTest
     protected fun doTest(testDataDir: String) {
         setupMppProjectFromDirStructure(File(testDataDir))
         val file = project.findFileWithCaret()
+        if (InTextDirectivesUtils.isDirectiveDefined(file.text, "ULTRA_LIGHT_CLASSES")) {
+            forceUsingUltraLightClassesForTest()
+        }
+
         val doc = PsiDocumentManager.getInstance(myProject).getDocument(file)!!
         val offset = doc.extractMarkerOffset(project, "<caret>")
         val editor = EditorFactory.getInstance().createEditor(doc, myProject)
@@ -65,4 +71,4 @@ abstract class AbstractKotlinGotoRelatedSymbolMultiModuleTest : AbstractKotlinNa
         val relatedItems = NavigationUtil.collectRelatedItems(source, null)
         return GotoTargetHandler.GotoData(source, relatedItems.map { it.element }.toTypedArray(), emptyList())
     }
-}
+}

idea/tests/org/jetbrains/kotlin/idea/navigation/KotlinGotoImplementationMultiModuleTestGenerated.java

@@ -25,6 +25,11 @@ public class KotlinGotoImplementationMultiModuleTestGenerated extends AbstractKo
         KotlinTestUtils.runTest(this::doTest, TargetBackend.ANY, testDataFilePath);
     }
 
+    @TestMetadata("actualTypeAliasWithAnonymousSubclass")
+    public void testActualTypeAliasWithAnonymousSubclass() throws Exception {
+        runTest("idea/testData/navigation/implementations/multiModule/actualTypeAliasWithAnonymousSubclass/");
+    }
+
     public void testAllFilesPresentInMultiModule() throws Exception {
         KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/navigation/implementations/multiModule"), Pattern.compile("^([^\\.]+)$"), TargetBackend.ANY, false);
     }