JS backend: basic support for class literals.

Added:
* the ability to get KClass using class literals (`::class`);
* the ability to get KClass from JsClass and vice versa;
* the ability to get simpleName.

 #KT-13345 Fixed

js/js.libraries/src/reflect/JsClass.kt

@@ -16,13 +16,24 @@
 
 package kotlin.js
 
+import kotlin.reflect.KClass
+import kotlin.reflect.js.internal.KClassImpl
+
 @native
 interface JsClass<T : Any> {
     val name: String
 }
 
 @native
+@Deprecated("Use class literal and extension property `js` instead.", replaceWith = ReplaceWith("T::class.js"))
 fun <T : Any> jsClass(): JsClass<T> = noImpl
 
+@Deprecated("Use class literal and extension property `js` instead.", replaceWith = ReplaceWith("this::class.js"))
 val <T : Any> T.jsClass: JsClass<T>
     get() = js("Object").getPrototypeOf(this).constructor
+
+val <T : Any> KClass<T>.js: JsClass<T>
+    get() = (this as KClassImpl<T>).jClass
+
+val <T : Any> JsClass<T>.kotlin: KClass<T>
+    get() = KClassImpl<T>(this)

js/js.libraries/src/reflect/KClassImpl.kt

@@ -0,0 +1,81 @@
+/*
+ * 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 kotlin.reflect.js.internal
+
+import kotlin.reflect.*
+
+internal class KClassImpl<T : Any>(
+        internal val jClass: JsClass<T>
+) : KClass<T> {
+
+    private val metadata = jClass.asDynamic().`$metadata$`
+    // TODO: use FQN
+    private val hashCode = simpleName?.hashCode() ?: 0
+
+    override val simpleName: String?
+        get() = metadata?.simpleName
+
+    override val annotations: List<Annotation>
+        get() = TODO()
+    override val constructors: Collection<KFunction<T>>
+        get() = TODO()
+    override val isAbstract: Boolean
+        get() = TODO()
+    override val isCompanion: Boolean
+        get() = TODO()
+    override val isData: Boolean
+        get() = TODO()
+    override val isFinal: Boolean
+        get() = TODO()
+    override val isInner: Boolean
+        get() = TODO()
+    override val isOpen: Boolean
+        get() = TODO()
+    override val isSealed: Boolean
+        get() = TODO()
+    override val members: Collection<KCallable<*>>
+        get() = TODO()
+    override val nestedClasses: Collection<KClass<*>>
+        get() = TODO()
+    override val objectInstance: T?
+        get() = TODO()
+    override val qualifiedName: String?
+        get() = TODO()
+    override val supertypes: List<KType>
+        get() = TODO()
+    override val typeParameters: List<KTypeParameter>
+        get() = TODO()
+    override val visibility: KVisibility?
+        get() = TODO()
+
+    override fun equals(other: Any?): Boolean {
+        return other is KClassImpl<*> && jClass == other.jClass
+    }
+
+    override fun hashCode(): Int {
+        return hashCode
+    }
+
+    override fun isInstance(value: Any?): Boolean {
+        TODO()
+    }
+
+    override fun toString(): String {
+        // TODO: use FQN
+        return "class $simpleName"
+    }
+}

js/js.libraries/src/reflect/reflection.kt

@@ -0,0 +1,44 @@
+/*
+ * 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.
+ */
+
+// a package is omitted to get declarations directly under the module
+
+import kotlin.reflect.KClass
+import kotlin.reflect.js.internal.KClassImpl
+
+@JsName("getKClass")
+private fun <T : Any> getKClass(jClass: JsClass<T>): KClass<T> = getOrCreateKClass(jClass)
+@JsName("getKClassFromExpression")
+private fun <T : Any> getKClassFromExpression(e: T): KClass<T> = getOrCreateKClass(e.jsClass)
+
+private fun <T : Any> getOrCreateKClass(jClass: JsClass<T>): KClass<T> {
+    val metadata = jClass.asDynamic().`$metadata$`
+
+    return if (metadata != null) {
+        if (metadata.`$kClass$` == null) {
+            val kClass = KClassImpl(jClass)
+            metadata.`$kClass$` = kClass
+            kClass
+        }
+        else {
+            metadata.`$kClass$`
+        }
+    }
+    else {
+        KClassImpl(jClass)
+    }
+}
+