As `ASTMangler` crashes when called on `ModuleDecl`, we simply use
its name.
This might probably not work reliably in a scenario where multiple
modules are compiled with the same name (like `main`), but this is left
for future work. At the moment this cannot create DB inconsistencies.
The `getName` in `Type.qll` was issuing a warning in other generated
classes having a `getName` from a `name` property in `schema.yml`.
To fix the possible inconsistency, `diagnostic_name` is being renamed to
`name` in the schema. Despite the scary doc comment on
`swift::Type::getString` (namely `for use in diagnostics only`), that
seems to be the right generic naming mechanism for types, and it
coincides with the name we were extracting on types with an explicit
`name` property.
In case we find a case where `Type::getString` gives something wrong,
we can probably just patch it on that specific type class.
This was temporarily broken as we were skipping full emission of all
entities without any valid location.
We now rely on `decl->getDeclContext()->getParentSourceFile()` which is
more robust.
