Support exposing Kotlin methods as Objective-C actions and outlets

Interop/Runtime/src/native/kotlin/kotlinx/cinterop/ObjectiveCImpl.kt

@@ -62,7 +62,11 @@ inline fun <T : ObjCObject?> interpretObjCPointerOrNull(rawPtr: NativePtr): T? =
     null
 }
 
-inline fun <T : ObjCObject?> interpretObjCPointer(rawPtr: NativePtr): T? = interpretObjCPointerOrNull<T>(rawPtr)!!
+inline fun <T : ObjCObject> interpretObjCPointer(rawPtr: NativePtr): T = if (rawPtr != nativeNullPtr) {
+    ObjCPointerHolder(rawPtr).uncheckedCast<T>()
+} else {
+    throw NullPointerException()
+}
 
 inline val ObjCObject.rawPtr: NativePtr get() = (this.uncheckedCast<ObjCPointerHolder>()).rawPtr
 inline val ObjCObject?.rawPtr: NativePtr get() = if (this != null) {
@@ -105,6 +109,10 @@ annotation class ObjCConstructor(val initSelector: String)
 @Retention(AnnotationRetention.BINARY)
 annotation class InteropStubs()
 
+@Target(AnnotationTarget.FUNCTION)
+@Retention(AnnotationRetention.SOURCE)
+private annotation class ObjCMethodImp(val selector: String, val encoding: String)
+
 @konan.internal.ExportForCompiler
 private fun <T : ObjCObject> allocObjCObject(clazz: NativePtr): T {
     val rawResult = objc_allocWithZone(clazz)

Interop/Runtime/src/native/kotlin/kotlinx/cinterop/ObjectiveCUtils.kt

@@ -28,4 +28,20 @@ inline fun <R> autoreleasepool(block: () -> R): R {
 // TODO: null checks
 var <T : ObjCObject?> ObjCObjectVar<T>.value: T
     get() = interpretObjCPointerOrNull<T>(nativeMemUtils.getNativePtr(this)).uncheckedCast<T>()
-    set(value) = nativeMemUtils.putNativePtr(this, value.rawPtr)
+    set(value) = nativeMemUtils.putNativePtr(this, value.rawPtr)
+
+/**
+ * Makes Kotlin method in Objective-C class accessible through Objective-C dispatch
+ * to be used as action sent by control in UIKit or AppKit.
+ */
+@Target(AnnotationTarget.FUNCTION)
+@Retention(AnnotationRetention.SOURCE)
+annotation class ObjCAction
+
+/**
+ * Makes Kotlin property in Objective-C class settable through Objective-C dispatch
+ * to be used as IB outlet.
+ */
+@Target(AnnotationTarget.PROPERTY)
+@Retention(AnnotationRetention.SOURCE)
+annotation class ObjCOutlet