swift234

IRGen: Kill the 'buildFakeType' abomination in GenericMetadataBuilder.

To instantiate the value witness table for generic types, we were instantiating the generic type at () for all of its parameters and hoping for the best. That's insane. Instead, let's use the DeclaredTypeInContext for the generic type so the archetypes actually get usefully bound inside the witnesses. This way, the witness implementations should be independent of generic parameters, so we can also mangle the unbound type into the witness symbols.

Swift SVN r7901