This is all effectively NFC, but lays out the shape of the iterative
type checker: requests are packaged up in TypeCheckRequest, we can
check whether the request has been satisfied already (isSatisfied),
enumerate its dependencies (enumerateDependenciesOf) in terms of other
TypeCheckRequests, and satisfy a request (satisfy).
Lazily-computed semantic information is captured directly in the
AST, but has been set aside in its own structure to allow us to
experiment with moving it into a lookaside table.
The only request that exists now is to type-check the superclass of
the given class. It currently performs unhealthy recursion into the
existing type checker. As we detangle dependencies, this recursion
between the IterativeTypeChecker and the TypeChecker can go away.
Swift SVN r32558
Having bound types in TypeReprs causes trouble in several places
(mostly involving type-checking of generics), and doesn't really fit
with TypeReprs being a mostly syntactic construct. Eliminate some code
paths using getBoundType(), and make the others do the same thing for
getBoundDecl() and getBoundType(). As part of the latter, provide
TypeBase::getDirectlyReferencedTypeDecl() to more easily map from type
to the named declaration.
Swift SVN r32018
