Each one has a different kind of lookup cache anyway, and there's no real
reason to have them share storage at the cost of type-safety.
Swift SVN r9242
docs/Resilience.rst describes the notion of a resilience component:
if the current source file is in the same component as a module being
used, it can use fragile access for everything in the other module,
with the assumption that everything in a component will always be
recompiled together.
However, nothing is actually using this today, and the interface we
have is probably not what we'll want in 2.0, when we actually implement
resilience.
Swift SVN r9174
This handles both Clang’s transitive inclusion and the use of
"adapter modules" to augment the Clang modules (e.g. Foundation.swift),
at the cost of a bit more memory (used to wrap all the Clang modules
in ClangModule objects). This is paving the way for making Sema
independent of ClangImporter.
Swift SVN r6698
This makes it very clear who is depending on special behavior at the
module level. Doing isa<ClangModule> now requires a header import; anything
more requires actually linking against the ClangImporter library.
If the current source file really can't import ClangModule.h, it can
still fall back to checking against the DeclContext's getContextKind()
(and indeed AST currently does in a few places).
Swift SVN r6695
