The macro name resolution in the source lookup cache was only looking at
macros in the current module, meaning that any names introduced by peer
or declaration macros declared in one module but used in another would
not be found by name lookup.
Switch the source lookup cache over to using the same
`forEachPotentialResolvedMacro` API that is used by lookup within
types, so we have consistent name-lookup-level macro resolution in both
places.
... except that would be horribly cyclic, of course, so introduce name
lookup flags to ignore top-level declarations introduced by macro
expansions. This is semantically correct because macro expansions are
not allowed to introduce new macros anyway, because that would have
been a terrible idea.
Fixes rdar://107321469. Peer and declaration macros at module scope
should work a whole lot better now.
Add a private discriminator to the mangling of an outermost-private `MacroExpansionDecl` so that declaration macros in different files won't have colliding macro expansion buffer names.
rdar://107462515
Make `SynthesizedFileUnit` attached to a `SourceFile`. This seemed like the
least ad-hoc approach to avoid doing unnecessary work for other `FileUnit`s.
TBDGen: when visiting a `SourceFile`, also visit its `SynthesizedFileUnit` if
it exists.
Serialization: do not treat `SynthesizedFileUnit` declarations as xrefs when
serializing the companion `SourceFile`.
Resolves TF-1239: AutoDiff test failures.
Add implicit declarations generated by the differentiation transform to a
`SynthesizedFileUnit` instead of an ad-hoc pre-existing `SourceFile`.
Resolves TF-1232: type reconstruction for AutoDiff-generated declarations.
Previously, type reconstruction failed because retroactively adding declarations
to a `SourceFile` did not update name lookup caches.
`SynthesizedFileUnit` is a container for synthesized declarations. Currently, it
only supports module-level declarations.
It is used by the SIL differentiation transform, which generates implicit struct
and enum declarations.
