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/frontend/src/org/jetbrains/kotlin/resolve/OverrideResolver.java

@@ -48,9 +48,14 @@ import static org.jetbrains.kotlin.resolve.OverridingUtil.OverrideCompatibilityI
 
 public class OverrideResolver {
     private final BindingTrace trace;
+    private final OverridesBackwardCompatibilityHelper overridesBackwardCompatibilityHelper;
 
-    public OverrideResolver(@NotNull BindingTrace trace) {
+    public OverrideResolver(
+            @NotNull BindingTrace trace,
+            @NotNull OverridesBackwardCompatibilityHelper overridesBackwardCompatibilityHelper
+    ) {
         this.trace = trace;
+        this.overridesBackwardCompatibilityHelper = overridesBackwardCompatibilityHelper;
     }
 
     public void check(@NotNull TopDownAnalysisContext c) {
@@ -650,7 +655,7 @@ public class OverrideResolver {
                 }
             });
         }
-        else if (!overriddenDescriptors.isEmpty()) {
+        else if (!overriddenDescriptors.isEmpty() && !overridesBackwardCompatibilityHelper.overrideCanBeOmitted(declared)) {
             CallableMemberDescriptor overridden = overriddenDescriptors.iterator().next();
             trace.report(VIRTUAL_MEMBER_HIDDEN.on(member, declared, overridden, overridden.getContainingDeclaration()));
         }

compiler/frontend/src/org/jetbrains/kotlin/resolve/OverridesBackwardCompatibilityHelper.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.resolve
+
+import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
+
+interface OverridesBackwardCompatibilityHelper {
+    fun overrideCanBeOmitted(overridingDescriptor: CallableMemberDescriptor): Boolean
+
+    object DEFAULT : OverridesBackwardCompatibilityHelper {
+        override fun overrideCanBeOmitted(overridingDescriptor: CallableMemberDescriptor): Boolean =
+                false
+    }
+}

compiler/frontend/src/org/jetbrains/kotlin/resolve/TargetPlatform.kt

@@ -51,7 +51,8 @@ abstract class TargetPlatform(val platformName: String) {
         override val platformConfigurator =
                 object : PlatformConfigurator(
                         DynamicTypesSettings(), listOf(), listOf(), listOf(), listOf(), listOf(),
-                        IdentifierChecker.DEFAULT, OverloadFilter.DEFAULT, PlatformToKotlinClassMap.EMPTY, DelegationFilter.DEFAULT
+                        IdentifierChecker.DEFAULT, OverloadFilter.DEFAULT, PlatformToKotlinClassMap.EMPTY, DelegationFilter.DEFAULT,
+                        OverridesBackwardCompatibilityHelper.DEFAULT
                 ) {
                     override fun configureModuleComponents(container: StorageComponentContainer) {
                         container.useInstance(SyntheticScopes.Empty)
@@ -97,7 +98,8 @@ abstract class PlatformConfigurator(
         private val identifierChecker: IdentifierChecker,
         private val overloadFilter: OverloadFilter,
         private val platformToKotlinClassMap: PlatformToKotlinClassMap,
-        private val delegationFilter: DelegationFilter
+        private val delegationFilter: DelegationFilter,
+        private val overridesBackwardCompatibilityHelper: OverridesBackwardCompatibilityHelper
 ) {
     private val declarationCheckers: List<DeclarationChecker> = DEFAULT_DECLARATION_CHECKERS + additionalDeclarationCheckers
     private val callCheckers: List<CallChecker> = DEFAULT_CALL_CHECKERS + additionalCallCheckers
@@ -117,6 +119,7 @@ abstract class PlatformConfigurator(
         useInstance(overloadFilter)
         useInstance(platformToKotlinClassMap)
         useInstance(delegationFilter)
+        useInstance(overridesBackwardCompatibilityHelper)
     }
 }