Support KClass.isInstance/cast/safeCast in stdlib-only reflection implementation

#KT-14720 Fixed

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/ClassReference.kt

@@ -30,7 +30,8 @@ public class ClassReference(override val jClass: Class<*>) : KClass<Any>, ClassB
         get() = error()
 
     @SinceKotlin("1.1")
-    override fun isInstance(value: Any?): Boolean = error()
+    override fun isInstance(value: Any?): Boolean =
+        isInstance(value, jClass)
 
     @SinceKotlin("1.1")
     override val typeParameters: List<KTypeParameter>
@@ -88,6 +89,15 @@ public class ClassReference(override val jClass: Class<*>) : KClass<Any>, ClassB
         jClass.toString() + Reflection.REFLECTION_NOT_AVAILABLE
 
     companion object {
+        private val FUNCTION_CLASSES =
+            listOf(
+                Function0::class.java, Function1::class.java, Function2::class.java, Function3::class.java, Function4::class.java,
+                Function5::class.java, Function6::class.java, Function7::class.java, Function8::class.java, Function9::class.java,
+                Function10::class.java, Function11::class.java, Function12::class.java, Function13::class.java, Function14::class.java,
+                Function15::class.java, Function16::class.java, Function17::class.java, Function18::class.java, Function19::class.java,
+                Function20::class.java, Function21::class.java, Function22::class.java
+            ).mapIndexed { i, clazz -> clazz to i }.toMap()
+
         private val primitiveFqNames = HashMap<String, String>().apply {
             put("boolean", "kotlin.Boolean")
             put("char", "kotlin.Char")
@@ -137,8 +147,8 @@ public class ClassReference(override val jClass: Class<*>) : KClass<Any>, ClassB
             primitiveFqNames.values.associateTo(this) { kotlinName ->
                 "kotlin.jvm.internal.${kotlinName.substringAfterLast('.')}CompanionObject" to "$kotlinName.Companion"
             }
-            for (arity in 0 until 23) {
-                put("kotlin.jvm.functions.Function$arity", "kotlin.Function$arity")
+            for ((klass, arity) in FUNCTION_CLASSES) {
+                put(klass.name, "kotlin.Function$arity")
             }
         }
 
@@ -174,5 +184,13 @@ public class ClassReference(override val jClass: Class<*>) : KClass<Any>, ClassB
             }
             else -> classFqNames[jClass.name] ?: jClass.canonicalName
         }
+
+        public fun isInstance(value: Any?, jClass: Class<*>): Boolean {
+            FUNCTION_CLASSES[jClass]?.let { arity ->
+                return TypeIntrinsics.isFunctionOfArity(value, arity)
+            }
+            val objectType = if (jClass.isPrimitive) jClass.kotlin.javaObjectType else jClass
+            return objectType.isInstance(value)
+        }
     }
 }

libraries/stdlib/src/kotlin/reflect/KClasses.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:kotlin.jvm.JvmName("KClasses")
+@file:Suppress("UNCHECKED_CAST")
+
+package kotlin.reflect
+
+/**
+ * Casts the given [value] to the class represented by this [KClass] object.
+ * Throws an exception if the value is `null` or if it is not an instance of this class.
+ *
+ * This is an experimental function that behaves as a similar function from kotlin.reflect.full on JVM.
+ *
+ * @see [KClass.isInstance]
+ * @see [KClass.safeCast]
+ */
+@SinceKotlin("1.3")
+@ExperimentalStdlibApi
+fun <T : Any> KClass<T>.cast(value: Any?): T {
+    if (!isInstance(value)) throw ClassCastException("Value cannot be cast to $qualifiedName")
+    return value as T
+}
+
+/**
+ * Casts the given [value] to the class represented by this [KClass] object.
+ * Returns `null` if the value is `null` or if it is not an instance of this class.
+ *
+ * This is an experimental function that behaves as a similar function from kotlin.reflect.full on JVM.
+ *
+ * @see [KClass.isInstance]
+ * @see [KClass.cast]
+ */
+@SinceKotlin("1.3")
+@ExperimentalStdlibApi
+fun <T : Any> KClass<T>.safeCast(value: Any?): T? {
+    return if (isInstance(value)) value as T else null
+}