KMP: Put "prohibit member scope mismatch for non-final expect" under the flag

^KT-61668 Fixed

Review: https://jetbrains.team/p/kt/reviews/12062/timeline

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated.java

@@ -610,6 +610,12 @@ public class FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated extends Abst
             runTest("compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/injectVarargParameterOverload.kt");
         }
 
+        @Test
+        @TestMetadata("memberScopeMismatch_oldLanguageVersion.kt")
+        public void testMemberScopeMismatch_oldLanguageVersion() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/memberScopeMismatch_oldLanguageVersion.kt");
+        }
+
         @Test
         @TestMetadata("nestedExpectOpenClass.kt")
         public void testNestedExpectOpenClass() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithPsiTestGenerated.java

@@ -610,6 +610,12 @@ public class FirOldFrontendMPPDiagnosticsWithPsiTestGenerated extends AbstractFi
             runTest("compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/injectVarargParameterOverload.kt");
         }
 
+        @Test
+        @TestMetadata("memberScopeMismatch_oldLanguageVersion.kt")
+        public void testMemberScopeMismatch_oldLanguageVersion() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/memberScopeMismatch_oldLanguageVersion.kt");
+        }
+
         @Test
         @TestMetadata("nestedExpectOpenClass.kt")
         public void testNestedExpectOpenClass() throws Exception {

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ActualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker.kt

@@ -25,6 +25,7 @@ import kotlin.contracts.contract
 
 object ActualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker : DeclarationChecker {
     override fun check(declaration: KtDeclaration, descriptor: DeclarationDescriptor, context: DeclarationCheckerContext) {
+        if (!context.languageVersionSettings.supportsFeature(LanguageFeature.MultiplatformRestrictions)) return
         val (actual, expect) = matchActualWithNonFinalExpect(declaration, descriptor, context) ?: return
 
         // The explicit casts won't be necessary when we start compiling kotlin with K2. K1 doesn't build CFG properly

compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/memberScopeMismatch_oldLanguageVersion.kt

@@ -0,0 +1,19 @@
+// FIR_IDENTICAL
+// LANGUAGE: -MultiplatformRestrictions
+// MODULE: m1-common
+// FILE: common.kt
+
+expect open class Foo {
+    fun existingMethod()
+    val existingParam: Int
+}
+
+// MODULE: m2-jvm()()(m1-common)
+// FILE: jvm.kt
+
+actual open class Foo {
+    actual fun existingMethod() {}
+    actual val existingParam: Int = 904
+
+    fun injectedMethod() {}
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -23605,6 +23605,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                     runTest("compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/injectVarargParameterOverload.kt");
                 }
 
+                @Test
+                @TestMetadata("memberScopeMismatch_oldLanguageVersion.kt")
+                public void testMemberScopeMismatch_oldLanguageVersion() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/memberScopeMismatch_oldLanguageVersion.kt");
+                }
+
                 @Test
                 @TestMetadata("nestedExpectOpenClass.kt")
                 public void testNestedExpectOpenClass() throws Exception {

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -278,6 +278,10 @@ enum class LanguageFeature(
     ProhibitUsingNullableTypeParameterAgainstNotNullAnnotated(sinceVersion = KOTLIN_1_9), // KT-36770
     NoSourceCodeInNotNullAssertionExceptions(KOTLIN_1_9, sinceApiVersion = ApiVersion.KOTLIN_1_4, kind = OTHER), // KT-57570
 
+    // 1.9.20 KMP stabilization. Unfortunately, we don't have 1.9.20 LV. So LV=1.9 is the best we can do.
+    // At least there won't be false positives for 1.8 users
+    MultiplatformRestrictions(KOTLIN_1_9, kind = BUG_FIX), // KT-61668
+
     // End of 1.* language features --------------------------------------------------
 
     // 2.0