Do not consider 'expect' class type constructors final

Because even a final expected class can be actualized with an open
actual class and thus have subtypes in the platform code

compiler/frontend/src/org/jetbrains/kotlin/psi/synthetics/SyntheticClassOrObjectDescriptor.kt

@@ -114,7 +114,6 @@ class SyntheticClassOrObjectDescriptor(
 
     private inner class SyntheticTypeConstructor(storageManager: StorageManager) : AbstractClassTypeConstructor(storageManager) {
         override fun getParameters(): List<TypeParameterDescriptor> = emptyList()
-        override fun isFinal(): Boolean = true
         override fun isDenotable(): Boolean = true
         override fun getDeclarationDescriptor(): ClassDescriptor = thisDescriptor
         override fun computeSupertypes(): Collection<KotlinType> = syntheticSupertypes

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassDescriptor.java

@@ -650,11 +650,6 @@ public class LazyClassDescriptor extends ClassDescriptorBase implements ClassDes
             return parameters.invoke();
         }
 
-        @Override
-        public boolean isFinal() {
-            return getModality() == Modality.FINAL;
-        }
-
         @Override
         public boolean isDenotable() {
             return true;

compiler/testData/diagnostics/tests/multiplatform/headerClass/implOpenClass.kt

@@ -6,6 +6,8 @@ expect class Foo
 
 expect fun getFoo(): Foo
 
+fun <T : Foo> bar() {} // no "Foo is final" warning should be here
+
 // MODULE: m2-jvm(m1-common)
 // FILE: jvm.kt
 

compiler/testData/diagnostics/tests/multiplatform/headerClass/implOpenClass.txt

@@ -1,6 +1,7 @@
 // -- Module: <m1-common> --
 package
 
+public fun </*0*/ T : Foo> bar(): kotlin.Unit
 public expect fun getFoo(): Foo
 
 public final expect class Foo {
@@ -13,6 +14,7 @@ public final expect class Foo {
 // -- Module: <m2-jvm> --
 package
 
+public fun </*0*/ T : Foo> bar(): kotlin.Unit
 public actual fun getFoo(): Foo
 
 public final class Bar : Foo {

compiler/testData/diagnostics/tests/multiplatform/headerClass/smartCastOnExpectClass.kt

@@ -0,0 +1,13 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+expect class Foo { // also, it's important that Foo doesn't override equals
+    fun foo()
+}
+
+fun check(x1: Foo, x: Any) {
+    if (x1 == x) {
+        x.<!UNRESOLVED_REFERENCE!>foo<!>()
+    }
+}

compiler/testData/diagnostics/tests/multiplatform/headerClass/smartCastOnExpectClass.txt

@@ -0,0 +1,10 @@
+package
+
+public fun check(/*0*/ x1: Foo, /*1*/ x: kotlin.Any): kotlin.Unit
+
+public final expect class Foo {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final expect fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -14241,6 +14241,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("smartCastOnExpectClass.kt")
+                public void testSmartCastOnExpectClass() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/smartCastOnExpectClass.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("superClass.kt")
                 public void testSuperClass() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/superClass.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -14241,6 +14241,12 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                     doTest(fileName);
                 }
 
+                @TestMetadata("smartCastOnExpectClass.kt")
+                public void testSmartCastOnExpectClass() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/smartCastOnExpectClass.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("superClass.kt")
                 public void testSuperClass() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/superClass.kt");