Open Radar

 
Summary:



Steps to Reproduce:
1. Run this:

	enum Tree: Printable {
		case Leaf(Int)
		case Branch(Int, [Tree])

		var children: [Tree] {
			switch self {
			case let Leaf:
				return []
			case let Branch(_, children):
				return children
			}
		}

		var description: String {
			switch self {
			case let Leaf(x):
				return ".Leaf(\(x))"
			case let Branch(x, children):
				let c = ",\n\t".join(map(children, toString))
				return ".Branch(\(x), [\n\t\(c)\n])"
			}
		}
	}

	let branch = Tree.Branch(1, [Tree.Leaf(2), Tree.Leaf(3)])
	println(branch.children)


Expected Results:
[.Leaf(2), .Leaf(3)]


Actual Results:
[]


Regression:
Workarounds:

1. Use a pattern after the constructor name:
	case let Leaf(_):
2. Remove `let`:
	case Leaf:

Notes:
This is incredibly serious. It’s trivial to accidentally use `let` when you’re not actually binding anything, and it will completely mask this error. I’m frankly astonished I haven’t encountered this before—I can only assume that’s because I usually bind all of the variables. Or maybe I _have_, and missed the bug. That’s pretty scary.