swift234

Finish up the last bit of work I plan on 
<rdar://problem/22333281> QoI: improve diagnostic when contextual type of closure disagrees with arguments

In the common case where someone doesn't care about the argument 
list to a closure, we now generate a tailored error message with a 
fixit to introduce the necessary "_,_ in " nonsense at the start 
of the closure.  IMO ideally we wouldn't require this, but until we
fix that type checker issue, we should at least give people the
obvious fix.


Swift SVN r31720