Open Radar

 
Summary:
Weird corner case.


Steps to Reproduce:
1. Compile this:
func unit<T>(x: T) -> T? { return x }
func f() -> Int? {
	return unit(1) ?? unit(2).map { 1 } ?? nil
}


Expected Results:
A clear error describing the fact that I’m passing () -> IntegerLiteralConvertible to map which expects Int -> Int.


Actual Results:
The compiler crashed.


Regression:
It doesn’t crash if you:
- remove the map
- only use two operands, and not three

It still crashes but doesn’t dump the stack trace if you use `unit(1)` as the third expression instead of nil:

    return unit(1) ?? unit(2).map { 1 } ?? unit(1)

It hangs the front-end outright (indefinitely) if you do that and also place the map on the first expression:

    return unit(1).map { 1 } ?? unit(1) ?? unit(1)


Notes:
This makes it look like the new front-end is a bit buggy too.