swift234

Minor cleanup for type validation: a type only needs to be validated once,
and type validation should never fail in a call to validateTypeSimple.

The one thing I really don't like about this whole approach is that we end
up with validateTypeSimple calls scattered all over the place...
the ultimate solution here is probably something along the lines of
introducing getUnvalidated() getters for types for use from the parser,
and make the standard getters for types assert that the type is valid
and perform any necessary computations themselves.



Swift SVN r2728