Thank you for kicking the tires on the new RustProtobuf implementation! You
can open an issue on github with a repro we can take a look.
> which go away if I hand edit the generated code to use the capitalized
Foo from the generated pub struct Foo
The general case in Rust you can't nest structs in structs (unlike, say, in
Java where you can put a class in a class). So the workaround for nested
types here is that we emit the Foo struct for the Foo message itself, and
then a `foo` mod for anything that is nested inside in the .proto file, so
in your example there *should* be a structure that looks like this:
```
struct Foo {...}
mod foo {
struct Inner { ... }
mod inner {
struct Context { ... }
}
}
}
```
The reason we do all of the super::super:: is so that you should be able to
put your gencode might be in some mod in your crate that isn't top level
(so handwritten code would probably write `crate::foo::inner::Context` but
we can't because it should work for you to make your own `mod proto` or
something that our gencode won't know about).
If you hand edited it to `super::super::super::Foo::inner::Context` and
that worked then something really weird is going on; these kind of nested
types are covered by tests and also widely used within Google and we
haven't gotten reports of the issue, so I would have to guess some form of
user-error (which maybe could be a documentation bug on our side).
> As a side note, the proto code builds perfectly under the 3.7.2
stepancheg release, so maybe this is a bleeding edge problem?
The 4.x release is a complete change compared to 3.x; what happened is that
he donated the crate name to Google. So it'll have a whole new set of
bugs 🙂
On Tue, Jan 20, 2026 at 12:19 PM Day Rush <[email protected]> wrote:
> Hi -
>
> I'm building an interface in rust to a large library of C & C# code that
> uses protocol buffers for it's IPC encoding. In the .proto files there are
> a lot of message structures like
>
> message Foo {
> message Inner {
> message Context {
> double field1 = 1;
> ... }
> google.protobuf.Timestamp at = 1;
> Context cx1 = 2;
> Context cx2 = 3;
> ... }
> double value = 1;
> repeated Inner inner_list = 2;
> ... }
>
> And the rust code generator doesn't appear to use consistent case folding
> in the generated code. Specifically, I see references to
>
> super::super::super::foo::inner::Context
>
> producing error messages like
>
> error[E0433]: failed to resolve: could not find `foo` in `super`
>
> which go away if I hand edit the generated code to use the capitalized Foo
> from the generated pub struct Foo. This seems like a bug, and I thought it
> would be good to check if there might be code generator option magic that I
> am missing.
>
> As a side note, the proto code builds perfectly under the 3.7.2 stepancheg
> release, so maybe this is a bleeding edge problem?
>
> Thanks in advance
> - d
>
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