Rather than performing a two-pass walk over all of the constraints in
the system to attach them to type variables, use the existing type
variable -> constraints mapping in the constraint graph to make this a
faster single-pass process. Also clarify the type bindings a little
bit. Improves type checking time for the standard library by ~3%.
Swift SVN r11098
This shaves about 10% off the number of solution states explored when
type-checking the standard library, although it doesn't improve
overall time by much. In a more targeted benchmark, 1 + 2.0 + 1, we
get a 21% speedup.
Swift SVN r11033
