Minimal support for Rust type aliases #1181
Conversation
The intention is to provide support to re-import Rust types already exported elsewhere into other bridges, creating equivalence of `extern "Rust"` types on the C++ side. Currently, the support is limited to re-exporting the type under the same name and the C++ namespace must be explicitly specified. Then, C++ functions can use the same type.
| if let RustType::Path(path) = &ty { | ||
| // OK, we support path | ||
| if let Some(last) = path.path.segments.last() { | ||
| if last.ident != alias.name.rust { |
There was a problem hiding this comment.
Not sure if we really need to prevent this - some may really want to use different names for the same Rust type.
There was a problem hiding this comment.
The problem is the C++ side. Effectively, what we want to do is to publish a forward declaration of the struct in question in the C++ code in the proper namespace (that's why also the namespace should match, otherwise the types are different on C++ side - currently, this is not checked, but probably should be).
If we'd like to support renaming the object, that would be possible, but again, that would require materializing both the forward declaration and some kind of type alias (e.g., using statement), so we would have both. The name would be accessible by both names and the original name taken anyway.
I.e., someone trying to rename the type to prevent name clashes would still end up with name clashes. Therefore, better to simply not allow renames.
The only way to do this properly would be to expose the original type in the original namespace and the alias name in a new namespace. However, due to the restriction on the Rust side, we only have access to tokens within our bridge, so there is no access to the original namespace (that's also the reason why the namespace must be re-specified).
There was a problem hiding this comment.
I see, thanks - I misunderstood the intention.
There was a problem hiding this comment.
Per #1187 (comment), I think all of this is already supported by cxx without the changes in this PR.
The intention is to provide support to re-import Rust types already exported elsewhere into other bridges, creating equivalence of
extern "Rust"types on the C++ side.Currently, the support is limited to re-exporting the type under the same name and the C++ namespace must be explicitly specified. Then, C++ functions can use the same type.