swift234

disallow destructuring a struct with a var, e.g.:

struct point { x : int, y : int }
var (a, b) = foo()  // when foo returns a 'point'

allowing this breaks our fragility model (e.g. members can be added/removed from the struct) and this generally needs to be integrated with our pattern matching stuff.  rdar://10934540



Swift SVN r1135