Method can be hidden if it is annotated with kotlin.internal.PlatformDependent,

or is a Java method from a Kotlin built-in class (transitively).

https://github.com/Kotlin/KEEP/blob/master/proposals/jdk-dependent-built-ins.md#backward-compatibility-of-overrides

compiler/testData/diagnostics/testsWithJava8/targetedBuiltIns/backwardCompatibility/basic.kt

@@ -0,0 +1,18 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER -PLATFORM_CLASS_MAPPED_TO_KOTLIN
+
+abstract class Test1 : Map<String, String> {
+    <!VIRTUAL_MEMBER_HIDDEN!>fun containsKey(key: String): Boolean<!> = TODO()
+
+    fun getOrDefault(key: String, defaultValue: String): String = TODO()
+}
+
+abstract class Test2 : MutableMap<String, String> {
+    fun replace(key: String, value: String): String? = TODO()
+}
+
+abstract class Test3 : java.util.AbstractMap<String, String>() {
+    <!VIRTUAL_MEMBER_HIDDEN!>fun containsKey(key: String): Boolean<!> = TODO()
+
+    fun replace(key: String, value: String): String? = TODO()
+}
+