Open Radar

 
The Swift Book - Tuple Pattern:
“You can constrain a tuple pattern to match certain kinds of tuple types by using type annotations. For example, the tuple pattern (x, y): (Int, Int) in the constant declaration let (x, y): (Int, Int) = (1, 2) matches only tuple types in which both elements are of type Int. To constrain only some elements of a tuple pattern, provide type annotations directly to those individual elements. For example, the tuple pattern in let (x: String, y) matches any two-element tuple type, as long as the first element is of type String.”

However, the syntax of individual element constraining does not work as expected. In real effect `x` is treated as the element name while `String` is treated as the variable.

Sample code: http://cl.ly/3n0b0k1e2B3a