Open Radar

 
Summary:
I ran into this error while working on ReactiveCocoa, specifically on this extension:

extension SignalProducer where T: SignalProducerType, E == T.E {
	@warn_unused_result(message="Did you forget to call `start` on the producer?")
	public func flatten(strategy: FlattenStrategy) -> SignalProducer<T.T, E> {
		return lift { (signal: Signal<T.T, E>) -> Signal<T.T, E> in
			return signal.flatten(strategy)
		}
	}
}

“Type of expression is ambiguous without more context” was, well, ambiguous.

Steps to Reproduce:
- Open attached project (ReactiveCocoa.xcworkspace)
- Compile ReactiveCocoa iOS framework

Expected Results:
Compilation fails in SignalProducer.swift:1100 with a more useful error, explaining which method it’s trying to find for what values of T and E, and ideally showing that it found a similar, compatible method.

Actual Results:
Compilation fails with error “Type of expression is ambiguous without more context”, but no more information.

Notes:
- The fix was to change the input signal of the closure to Signal<T, E> (instead of T.T).
- Note that this is in some intermediate state while I was working on a feature, so tests (and possibly other things) are currently broken.