Implement v0.6 Optional Bytes
This makes a few changes:
- It changes generated messages to reference message innards as a type in `__runtime` instead of branching on what fields should be there. That results in much less bifurcation in gencode and lets runtime-agnostic code reference raw message innards.
- It adds a generic mechanism for creating vtable-based mutators. These vtables point to thunks generated for interacting with C++ or upb fields. Right now, the design results in 2-word (msg+vtable) mutators for C++ and 3-word mutators (msg+arena+vtable) for UPB. See upb.rs for an explanation of the design options. I chose the `RawMessage+&Arena` design for mutator data as opposed to a `&MessageInner` design because it did not result in extra-indirection layout changes for message mutators. We could revisit this in the future with performance data, since this results in all field mutators being 3 words large instead of the register-friendly 2 words.
- And lastly, as a nearby change that touches on many of the same topics, it adds some extra SAFETY comments for Send/Sync in message gencode.
PiperOrigin-RevId: 559483437
diff --git a/rust/internal.rs b/rust/internal.rs
index 7423a3c..c1d8dca 100644
--- a/rust/internal.rs
+++ b/rust/internal.rs
@@ -32,6 +32,9 @@
//! exposed to through the `protobuf` path but must be public for use by
//! generated code.
+pub use crate::vtable::{
+ new_vtable_field_entry, BytesMutVTable, BytesOptionalMutVTable, RawVTableMutator,
+};
use std::slice;
/// Used to protect internal-only items from being used accidentally.
