Deal with cases when different visibility of overridden members could produce incorrect fake override.

(by Pavel Talanov and Andrey Breslav)

compiler/testData/diagnostics/tests/override/AllPrivateFromSuperTypes.kt

@@ -0,0 +1,14 @@
+package test
+
+trait A {
+    private val a: String
+      get() = "AAAA!"
+}
+
+open class C {
+    private val a: String = ""
+}
+
+class Subject : C(), A {
+    val c = <!INVISIBLE_MEMBER!>a<!>
+}

compiler/testData/diagnostics/tests/override/AllProtectedFromSupertypes.kt

@@ -0,0 +1,13 @@
+package test
+
+trait A {
+    protected val a: String
+}
+
+open class C {
+    protected val a: String = ""
+}
+
+class Subject : C(), A {
+    val c = a
+}

compiler/testData/diagnostics/tests/override/ProtectedAndPrivateFromSupertypes.kt

@@ -0,0 +1,17 @@
+package test
+
+trait A {
+    protected val a: String
+}
+
+trait B {
+    protected val a: String
+}
+
+open class C {
+    private val a: String = ""
+}
+
+class <!ABSTRACT_MEMBER_NOT_IMPLEMENTED!>Subject<!> : C(), A, B {
+    val c = a
+}