We already ban all structs from declaring storage that comes from implementation-only imports. Until now we missed property wrappers, they were just dropped in deserialization.
Resolves rdar://problem/59403617
These also create a dependency on the implementation module, even if
both the type and the protocol are public. As John puts it, a
conformance is basically a declaration that we name as part of another
declaration.
More rdar://problem/48991061
Based on the existing access checker for types used in decls. There's
a common skeleton here but we can't seem to get it out, so for now
add a third DeclVisitor to this file. On the plus side, checking this
alongside access is an easy way to make sure everything gets checked.
Part of rdar://problem/48991061
