Parameterize the resolution of generic type parameter types to archetypes.

When type checking, allow the caller to customize the resolution of generic
type parameter types based on the context, for example, by choosing to
substitute in an archetype (or not) and allowing one to resolve a dependent
member reference via a specific archetype.

No actual functionality change here.


Swift SVN r8797

lib/Serialization/Serialization.cpp

@@ -1525,10 +1525,11 @@ void Serializer::writeType(Type ty) {
     auto dependent = cast<DependentMemberType>(ty.getPointer());
 
     unsigned abbrCode = DeclTypeAbbrCodes[DependentMemberTypeLayout::Code];
+    assert(dependent->getAssocType() && "Unchecked dependent member type");
     DependentMemberTypeLayout::emitRecord(
       Out, ScratchRecord, abbrCode,
       addTypeRef(dependent->getBase()),
-      addIdentifierRef(dependent->getName()));
+      addDeclRef(dependent->getAssocType()));
     break;
   }