[FE] Prohibit protected members in final expected or actual classes

^KT-28850 Fixed

compiler/testData/diagnostics/tests/modifiers/protectedInExpectActual.kt

@@ -0,0 +1,48 @@
+// LANGUAGE: +MultiPlatformProjects
+// !DIAGNOSTICS: -NO_ACTUAL_FOR_EXPECT, -ACTUAL_WITHOUT_EXPECT
+// FIR_IDENTICAL
+class SimpleClass {
+    protected fun foo() = Unit
+}
+
+expect class ExpClass {
+    <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> fun foo()
+
+    <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> val bar: Int
+}
+
+actual class ActClass {
+    actual <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> fun foo() = Unit
+
+    actual <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> val bar: Int = 42
+}
+
+expect open class ExpOpenClass {
+    protected fun foo()
+}
+
+actual open class ActOpenClass {
+    actual protected fun foo() = Unit
+}
+
+enum class SimpleEnum {
+    ENTRY;
+
+    protected fun foo() = Unit
+}
+
+expect enum class ExpEnumClass {
+    ENTRY;
+
+    <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> fun foo()
+
+    <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> val bar: Int
+}
+
+actual enum class ActEnumClass {
+    ENTRY;
+
+    actual <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> fun foo() = Unit
+
+    <!WRONG_MODIFIER_CONTAINING_DECLARATION!>protected<!> val bar: Int = 42
+}