Guard against a potential infinite feedback loop.

Author: andersio

ReactiveObjC/NSObject+RACSelectorSignal.m

@@ -71,14 +71,18 @@ static void RACSwizzleForwardInvocation(Class class) {
 		if ([baseClass instancesRespondToSelector:aliasOfOriginalSelector]) {
 			// `self` uses a runtime subclass generated by third-party APIs, and RAC
 			// found an existing implementation for the selector at the setup time.
-			// Call that implementation.
+			// Call that implementation if it is not the ObjC message forwarder.
 			Method xchgMethod = class_getInstanceMethod(baseClass, aliasOfOriginalSelector);
 			IMP impl = method_getImplementation(xchgMethod);
 
-			IMP oldImpl = class_replaceMethod(baseClass, originalSelector, impl, method_getTypeEncoding(xchgMethod));
-			invocation.selector = originalSelector;
-			[invocation invoke];
-			class_replaceMethod(baseClass, originalSelector, oldImpl, method_getTypeEncoding(xchgMethod));
+			if (impl != _objc_msgForward) {
+				IMP oldImpl = class_replaceMethod(baseClass, originalSelector, impl, method_getTypeEncoding(xchgMethod));
+				invocation.selector = originalSelector;
+				[invocation invoke];
+				class_replaceMethod(baseClass, originalSelector, oldImpl, method_getTypeEncoding(xchgMethod));
+			} else {
+				forward = YES;
+			}
 		} else if ([superclass instancesRespondToSelector:originalSelector]) {
 			// The stated class has an implementation of the selector. Call that
 			// implementation if it is not the ObjC message forwarder.