swift234

Reject obvious inout argument aliases with a good diagnostic, for example:

t2.swift:4:11: error: inout arguments are not allowed to alias each other
 swap(&x, &x)
          ^~
t2.swift:4:7: note: previous aliasing argument
 swap(&x, &x)
      ^~

This can (and arguably should) also be handled with a later diagnostic pass, but
handling it in SILGen gives us full range emission capability.



Swift SVN r20469