swift234

Encode and pass all of the archetypes, including derived archetypes,
in SpecializeExpr, so that we have complete substitution and
protocol-conformance information. On the IR generation side, pass
witness tables for all of the archetypes (again, including derived
archetypes) into generic functions, so that we have witness tables for
all of the associated types.

There are at least two major issues:

  (1) This is a terribly inefficient way to pass witness tables for
  associated types. The witness tables for associated types should be
  accessible via the witness tables of their parent. However, we need
  more information in the ASTs here, because there may be additional
  witness tables that will need to be passed for requirements that are
  placed on the associated type by the generic function itself.

  (2) Something about my test triggers a void/non-void verification failure
  in the witness build for an instance function whose abstracted form
  returns an associated type archetype and whose concrete form returns
  an empty struct. See the FIXME in the test.



Swift SVN r2464