Open Radar

 
Summary:
My motivation for filing this bug report is a problem discovered concurrently with rdar://17132238. When using the result of an incorrectly called function as the input to an arithmetic operator, Xcode obscures the underlying error with a cryptic error about the operator.

Steps to Reproduce:
1. Enter the following code in a playground:

 For example, this code:

func sumOf(numbers: Int...) -> Int {
	var sum = 0
	for number in numbers {
		sum += number
	}
	return sum
}

func averageOf(numbers: Int...) -> Float {
	return Float(sumOf(numbers)) / Float(numbers.count)
}
averageOf(1, 2, 3)



Expected Results:
An error message informing the programmer that sumOf() is being called with a bad argument, as will be seen if that call is made on its own line. In that case, the error message will be “Could not find an overload for ‘__conversion’ that accepts the supplied arguments”, which is more descriptive of the actual error here (though still not great).

Actual Results:
averageOf()’s return statement provokes the following error message: “Could not find an overload for ‘/‘ that accepts the supplied arguments”.

Notes:
The following code demonstrates this problem:

func sumOf(numbers: Int...) -> Int {
	var sum = 0
	for number in numbers {
		sum += number
	}
	return sum
}
sumOf(42, 597, 12)

func averageOf(numbers: Int...) -> Float {
	return Float(sumOf(numbers)) / Float(numbers.count)
}

averageOf(42, 597, 12, 18)