diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRendererUtil.kt b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRendererUtil.kt
index 96ccad4021a..a1215c4f7e7 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRendererUtil.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DiagnosticRendererUtil.kt
@@ -23,3 +23,5 @@ import org.jetbrains.kotlin.renderer.DescriptorRendererImpl
 public fun <P> renderParameter(parameter: P, renderer: Renderer<P>?): Any = renderer?.render(parameter) ?: parameter
 
 public fun ClassDescriptor.renderKindWithName(): String = "${DescriptorRendererImpl.getClassKindPrefix(this)} '${getName()}'"
+
+public fun ClassDescriptor.renderKind(): String = DescriptorRendererImpl.getClassKindPrefix(this)
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/localClassifier.kt b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/localClassifier.kt
new file mode 100644
index 00000000000..4b421b320df
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/localClassifier.kt
@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+fun foo() {
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>class A<!> {
+        inner <!NON_TOPLEVEL_CLASS_DECLARATION!>class E<!> {
+            <!NESTED_CLASS_NOT_ALLOWED, NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!>
+        }
+    }
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!> {
+    }
+}
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/localClassifier.txt b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/localClassifier.txt
new file mode 100644
index 00000000000..093bfc34070
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/localClassifier.txt
@@ -0,0 +1,3 @@
+package
+
+internal fun foo(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.kt b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.kt
new file mode 100644
index 00000000000..a4e17120965
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.kt
@@ -0,0 +1,95 @@
+class A {
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!> {
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>class C<!>
+
+        inner <!NON_TOPLEVEL_CLASS_DECLARATION!>class D<!>
+
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!> {
+            <!NON_TOPLEVEL_CLASS_DECLARATION!>trait A<!>
+            <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!>
+        }
+
+        companion object {}
+    }
+
+    inner <!NON_TOPLEVEL_CLASS_DECLARATION!>class I<!>
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!> {
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>trait A<!>
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!>
+
+        companion object {}
+    }
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>enum class E<!> {
+        X Y
+
+        companion object {}
+    }
+
+    companion object {}
+}
+
+trait T {
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!> {
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>class C<!>
+
+        inner <!NON_TOPLEVEL_CLASS_DECLARATION!>class D<!>
+
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!> {
+            <!NON_TOPLEVEL_CLASS_DECLARATION!>trait A<!>
+            <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!>
+        }
+
+        companion object {}
+    }
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!> {
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>trait A<!>
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!>
+
+        companion object {}
+    }
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>enum class E<!> {
+        X Y
+
+        companion object {}
+    }
+
+    companion object {}
+}
+
+enum class E {
+    X Y
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!> {
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>class C<!>
+
+        inner <!NON_TOPLEVEL_CLASS_DECLARATION!>class D<!>
+
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!> {
+            <!NON_TOPLEVEL_CLASS_DECLARATION!>trait A<!>
+            <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!>
+        }
+
+        companion object {}
+    }
+
+    inner <!NON_TOPLEVEL_CLASS_DECLARATION!>class I<!>
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>trait T<!> {
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>trait A<!>
+        <!NON_TOPLEVEL_CLASS_DECLARATION!>class B<!>
+
+        companion object {}
+    }
+
+    <!NON_TOPLEVEL_CLASS_DECLARATION!>enum class E<!> {
+        X Y
+
+        companion object {}
+    }
+
+    companion object {}
+}
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.txt b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.txt
new file mode 100644
index 00000000000..b26fe7edf68
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.txt
@@ -0,0 +1,425 @@
+package
+
+internal final class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal final class B {
+        public constructor B()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal final class C {
+            public constructor C()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal final inner class D {
+            public constructor D()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal trait T {
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+            internal trait A {
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+            }
+
+            internal final class B {
+                public constructor B()
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+            }
+        }
+    }
+
+    internal companion object Companion {
+        private constructor Companion()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final enum class E : kotlin.Enum<A.E> {
+        public enum entry X : A.E {
+            private constructor X()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: A.E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        public enum entry Y : A.E {
+            private constructor Y()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: A.E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        private constructor E()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: A.E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        // Static members
+        public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): A.E
+        public final /*synthesized*/ fun values(): kotlin.Array<A.E>
+    }
+
+    internal final inner class I {
+        public constructor I()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal trait T {
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal trait A {
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal final class B {
+            public constructor B()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}
+
+internal final enum class E : kotlin.Enum<E> {
+    public enum entry X : E {
+        private constructor X()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public enum entry Y : E {
+        private constructor Y()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    private constructor E()
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+    public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal final class B {
+        public constructor B()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal final class C {
+            public constructor C()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal final inner class D {
+            public constructor D()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal trait T {
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+            internal trait A {
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+            }
+
+            internal final class B {
+                public constructor B()
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+            }
+        }
+    }
+
+    internal companion object Companion {
+        private constructor Companion()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final enum class E : kotlin.Enum<E.E> {
+        public enum entry X : E.E {
+            private constructor X()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E.E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        public enum entry Y : E.E {
+            private constructor Y()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E.E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        private constructor E()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E.E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        // Static members
+        public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): E.E
+        public final /*synthesized*/ fun values(): kotlin.Array<E.E>
+    }
+
+    internal final inner class I {
+        public constructor I()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal trait T {
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal trait A {
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal final class B {
+            public constructor B()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+
+    // Static members
+    public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): E
+    public final /*synthesized*/ fun values(): kotlin.Array<E>
+}
+
+internal trait T {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal final class B {
+        public constructor B()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal final class C {
+            public constructor C()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal final inner class D {
+            public constructor D()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal trait T {
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+            internal trait A {
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+            }
+
+            internal final class B {
+                public constructor B()
+                public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+                public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+                public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+            }
+        }
+    }
+
+    internal companion object Companion {
+        private constructor Companion()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final enum class E : kotlin.Enum<T.E> {
+        public enum entry X : T.E {
+            private constructor X()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: T.E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        public enum entry Y : T.E {
+            private constructor Y()
+            public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: T.E): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+            public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        private constructor E()
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: T.E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        // Static members
+        public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): T.E
+        public final /*synthesized*/ fun values(): kotlin.Array<T.E>
+    }
+
+    internal trait T {
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        internal trait A {
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal final class B {
+            public constructor B()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+
+        internal companion object Companion {
+            private constructor Companion()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestWithJsStdLibGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestWithJsStdLibGenerated.java
index e3b3994a106..b98547d8131 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestWithJsStdLibGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestWithJsStdLibGenerated.java
@@ -34,6 +34,7 @@ import java.util.regex.Pattern;
         JetDiagnosticsTestWithJsStdLibGenerated.DynamicTypes.class,
         JetDiagnosticsTestWithJsStdLibGenerated.JsCode.class,
         JetDiagnosticsTestWithJsStdLibGenerated.Native.class,
+        JetDiagnosticsTestWithJsStdLibGenerated.UnsupportedFeatures.class,
 })
 @RunWith(JUnit3RunnerWithInners.class)
 public class JetDiagnosticsTestWithJsStdLibGenerated extends AbstractJetDiagnosticsTestWithJsStdLib {
@@ -551,4 +552,25 @@ public class JetDiagnosticsTestWithJsStdLibGenerated extends AbstractJetDiagnost
             }
         }
     }
+
+    @TestMetadata("compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class UnsupportedFeatures extends AbstractJetDiagnosticsTestWithJsStdLib {
+        public void testAllFilesPresentInUnsupportedFeatures() throws Exception {
+            JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures"), Pattern.compile("^(.+)\\.kt$"), true);
+        }
+
+        @TestMetadata("localClassifier.kt")
+        public void testLocalClassifier() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/localClassifier.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("nestedInnerClassifier.kt")
+        public void testNestedInnerClassifier() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.kt");
+            doTest(fileName);
+        }
+    }
 }
diff --git a/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/KotlinJsCheckerProvider.kt b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/KotlinJsCheckerProvider.kt
index 03319b3b772..053f35f9167 100644
--- a/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/KotlinJsCheckerProvider.kt
+++ b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/KotlinJsCheckerProvider.kt
@@ -20,7 +20,7 @@ import org.jetbrains.kotlin.js.resolve.diagnostics.JsCallChecker
 import org.jetbrains.kotlin.resolve.AdditionalCheckerProvider
 
 public object KotlinJsCheckerProvider : AdditionalCheckerProvider(
-        additionalDeclarationCheckers = listOf(NativeInvokeChecker(), NativeGetterChecker(), NativeSetterChecker()),
+        additionalDeclarationCheckers = listOf(NativeInvokeChecker(), NativeGetterChecker(), NativeSetterChecker(), ClassDeclarationChecker()),
         additionalCallCheckers = listOf(JsCallChecker()),
         additionalTypeCheckers = listOf()
 )
diff --git a/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/DefaultErrorMessagesJs.kt b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/DefaultErrorMessagesJs.kt
index 912f28ad40a..a51a400d28d 100644
--- a/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/DefaultErrorMessagesJs.kt
+++ b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/DefaultErrorMessagesJs.kt
@@ -36,6 +36,7 @@ private val DIAGNOSTIC_FACTORY_TO_RENDERER by Delegates.lazy {
         put(ErrorsJs.JSCODE_ARGUMENT_SHOULD_BE_CONSTANT, "Argument must be string constant")
         put(ErrorsJs.NOT_SUPPORTED, "Cannot translate (not supported yet): ''{0}''", RenderFirstLineOfElementText)
         put(ErrorsJs.REFERENCE_TO_BUILTIN_MEMBERS_NOT_SUPPORTED, "Callable references for builtin members are not supported yet: ''{0}''", RenderFirstLineOfElementText)
+        put(ErrorsJs.NON_TOPLEVEL_CLASS_DECLARATION, "Non-toplevel {0} declarations not supported yet", Renderers.STRING)
 
 
         this
diff --git a/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/ErrorsJs.java b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/ErrorsJs.java
index 70656874812..04f4441dba4 100644
--- a/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/ErrorsJs.java
+++ b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/diagnostics/ErrorsJs.java
@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.diagnostics.Errors;
 import org.jetbrains.kotlin.psi.JetDeclaration;
 import org.jetbrains.kotlin.psi.JetElement;
 import org.jetbrains.kotlin.psi.JetExpression;
+import org.jetbrains.kotlin.psi.JetNamedDeclaration;
 import org.jetbrains.kotlin.types.JetType;
 
 import static org.jetbrains.kotlin.diagnostics.PositioningStrategies.*;
@@ -41,6 +42,7 @@ public interface ErrorsJs {
     DiagnosticFactory0<JetExpression> JSCODE_ARGUMENT_SHOULD_BE_CONSTANT = DiagnosticFactory0.create(ERROR, DEFAULT);
     DiagnosticFactory1<JetElement, JetElement> NOT_SUPPORTED = DiagnosticFactory1.create(ERROR, DEFAULT);
     DiagnosticFactory1<JetElement, JetElement> REFERENCE_TO_BUILTIN_MEMBERS_NOT_SUPPORTED = DiagnosticFactory1.create(ERROR, DEFAULT);
+    DiagnosticFactory1<JetNamedDeclaration, String> NON_TOPLEVEL_CLASS_DECLARATION = DiagnosticFactory1.create(ERROR, DECLARATION_NAME);
 
     @SuppressWarnings("UnusedDeclaration")
     Object _initializer = new Object() {
diff --git a/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/unsupportedFeatureCheckers.kt b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/unsupportedFeatureCheckers.kt
new file mode 100644
index 00000000000..8ac9a876d8a
--- /dev/null
+++ b/js/js.frontend/src/org/jetbrains/kotlin/js/resolve/unsupportedFeatureCheckers.kt
@@ -0,0 +1,45 @@
+/*
+ * Copyright 2010-2015 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.js.resolve
+
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
+import org.jetbrains.kotlin.descriptors.DeclarationDescriptorWithVisibility
+import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.diagnostics.DiagnosticSink
+import org.jetbrains.kotlin.diagnostics.rendering.renderKind
+import org.jetbrains.kotlin.diagnostics.rendering.renderKindWithName
+import org.jetbrains.kotlin.js.resolve.diagnostics.ErrorsJs
+import org.jetbrains.kotlin.js.translate.utils.AnnotationsUtils
+import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.resolve.DeclarationChecker
+import org.jetbrains.kotlin.resolve.DescriptorUtils
+
+class ClassDeclarationChecker : DeclarationChecker {
+    override fun check(declaration: JetDeclaration, descriptor: DeclarationDescriptor, diagnosticHolder: DiagnosticSink) {
+
+        if (declaration !is JetClassOrObject || declaration is JetObjectDeclaration || declaration is JetEnumEntry) return
+
+        // hack to avoid to get diagnostics when compile kotlin builtins
+        val fqNameUnsafe = DescriptorUtils.getFqName(descriptor)
+        if (fqNameUnsafe.asString().startsWith("kotlin.")) return
+
+        if (!DescriptorUtils.isTopLevelDeclaration(descriptor) && !AnnotationsUtils.isNativeObject(descriptor)) {
+            diagnosticHolder.report(ErrorsJs.NON_TOPLEVEL_CLASS_DECLARATION.on(declaration, (descriptor as ClassDescriptor).renderKind()))
+        }
+    }
+}