Reflection: add KClass.isInstance, KClass.cast, KClass.safeCast

#KT-11284 Fixed

core/builtins/src/kotlin/reflect/KClass.kt

@@ -58,6 +58,11 @@ public interface KClass<T : Any> : KDeclarationContainer, KAnnotatedElement, KCl
      */
     public val objectInstance: T?
 
+    /**
+     * Returns `true` if [value] is an instance of this class on a given platform.
+     */
+    public fun isInstance(value: Any?): Boolean
+
     /**
      * The list of type parameters of this class. This list does *not* include type parameters of outer classes.
      */

core/descriptors.runtime/src/org/jetbrains/kotlin/load/java/structure/reflect/reflectClassUtil.kt

@@ -27,13 +27,29 @@ val Class<*>.safeClassLoader: ClassLoader
 fun Class<*>.isEnumClassOrSpecializedEnumEntryClass(): Boolean =
         Enum::class.java.isAssignableFrom(this)
 
-private val WRAPPER_TO_PRIMITIVE = listOf(
-       Boolean::class, Byte::class, Char::class, Double::class, Float::class, Int::class, Long::class, Short::class
-).map { it.javaObjectType to it.javaPrimitiveType }.toMap()
+private val PRIMITIVE_CLASSES =
+        listOf(Boolean::class, Byte::class, Char::class, Double::class, Float::class, Int::class, Long::class, Short::class)
+private val WRAPPER_TO_PRIMITIVE = PRIMITIVE_CLASSES.map { it.javaObjectType to it.javaPrimitiveType }.toMap()
+private val PRIMITIVE_TO_WRAPPER = PRIMITIVE_CLASSES.map { it.javaPrimitiveType to it.javaObjectType }.toMap()
 
 val Class<*>.primitiveByWrapper: Class<*>?
     get() = WRAPPER_TO_PRIMITIVE[this]
 
+val Class<*>.wrapperByPrimitive: Class<*>?
+    get() = PRIMITIVE_TO_WRAPPER[this]
+
+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()
+
+val Class<*>.functionClassArity: Int?
+    get() = FUNCTION_CLASSES[this]
+
 /**
  * NOTE: does not perform a Java -> Kotlin mapping. If this is not expected, consider using KClassImpl#classId instead
  */

core/reflection.jvm/src/kotlin/reflect/KClasses.kt

@@ -236,3 +236,29 @@ fun KClass<*>.isSubclassOf(base: KClass<*>): Boolean =
  */
 fun KClass<*>.isSuperclassOf(derived: KClass<*>): Boolean =
         derived.isSubclassOf(this)
+
+
+/**
+ * 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.
+ *
+ * @see [KClass.isInstance]
+ * @see [KClass.safeCast]
+ */
+@Suppress("UNCHECKED_CAST")
+fun <T : Any> KClass<T>.cast(value: Any?): T {
+    if (!isInstance(value)) throw TypeCastException("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.
+ *
+ * @see [KClass.isInstance]
+ * @see [KClass.cast]
+ */
+@Suppress("UNCHECKED_CAST")
+fun <T : Any> KClass<T>.safeCast(value: Any?): T? {
+    return if (isInstance(value)) value as T else null
+}

core/reflection.jvm/src/kotlin/reflect/jvm/internal/KClassImpl.kt

@@ -20,6 +20,8 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotated
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.load.java.JvmAbi
+import org.jetbrains.kotlin.load.java.structure.reflect.functionClassArity
+import org.jetbrains.kotlin.load.java.structure.reflect.wrapperByPrimitive
 import org.jetbrains.kotlin.load.kotlin.header.KotlinClassHeader
 import org.jetbrains.kotlin.load.kotlin.reflect.ReflectKotlinClass
 import org.jetbrains.kotlin.name.ClassId
@@ -27,6 +29,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.serialization.deserialization.findClassAcrossModuleDependencies
+import kotlin.jvm.internal.TypeIntrinsics
 import kotlin.reflect.*
 
 internal class KClassImpl<T : Any>(override val jClass: Class<T>) :
@@ -136,6 +139,14 @@ internal class KClassImpl<T : Any>(override val jClass: Class<T>) :
     override val objectInstance: T?
         get() = objectInstance_()
 
+    override fun isInstance(value: Any?): Boolean {
+        // TODO: use Kotlin semantics for mutable/read-only collections once KT-11754 is supported (see TypeIntrinsics)
+        jClass.functionClassArity?.let { arity ->
+            return TypeIntrinsics.isFunctionOfArity(value, arity)
+        }
+        return (jClass.wrapperByPrimitive ?: jClass).isInstance(value)
+    }
+
     override val typeParameters: List<KTypeParameter>
         get() = descriptor.declaredTypeParameters.map(::KTypeParameterImpl)
 

core/runtime.jvm/src/kotlin/jvm/internal/ClassReference.kt

@@ -40,6 +40,8 @@ class ClassReference(override val jClass: Class<*>) : KClass<Any>, ClassBasedDec
     override val objectInstance: Any?
         get() = error()
 
+    override fun isInstance(value: Any?): Boolean = error()
+
     override val typeParameters: List<KTypeParameter>
         get() = error()