Open Radar

 
Summary:
When an identifier is bound in a case-let expression the exhaustiveness checker does not appear to consider it covered as in

func op(this : Optional<Bool>, other : Optional<Bool>) -> Optional<Bool> {
	switch (this, other) {
	case let (.None, w):
		return w
	case let (w, .None):
		return w
	case let (.Some(e1), .Some(e2)):
		return .Some(e1 && e2)
	} // cases are non-exhaustive, consider adding default clause
}

Despite such a definition being acceptable in languages like ML and Haskell.  However, when the case-lets are changed to simple cases the exhaustiveness checker stops complaining about the same expression.

func op(this : Optional<Bool>, other : Optional<Bool>) -> Optional<Bool> {
	switch (this, other) {
	case (.None, _):
		return .None
	case (_, .None):
		return .None
	case let (.Some(e1), .Some(e2)):
		return .Some(e1 && e2)
	} // All clear
}

The checker should consider tuple expressions with identifiers bound in case-lets as wildcards in plain cases.

Steps to Reproduce:
1. Declare both of those functions in a playground.

Expected Results:
The exhaustiveness checker reports both as exhaustive.

Actual Results:
The exhaustiveness checker rejects the former and accepts the latter.

Version:
Xcode 7.0 beta 3 (7A152u)

Notes:


Configuration:


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