swift234

Fix <rdar://problem/20365753> Bogus diagnostic "refutable pattern match can fail"

We do this by banning single-element tuple patterns with a label (in most cases).
We now produce:
x.swift:2:8: error: label is not allowed on single element tuple pattern
  let (responseObject: Int?) = f()
       ^
x.swift:2:7: note: remove the parentheses to make this a type annotation
  let (responseObject: Int?) = f()
      ^                    ~
                           
x.swift:2:8: note: remove the label to make this a tuple pattern
  let (responseObject: Int?) = f() 
       ^~~~~~~~~~~~~~~




Swift SVN r26898