type-signature

Compile-time structural signatures for Rust types.

Every type that implements [TypeSignature] exposes a SIGNATURE derived from the type's name, generic arguments, and field/variant layout. If the layout changes in a way that could be a breaking change for consumers, the hash changes.

This is useful for:

• Schema drift detection: pin a CONST_HASH in a const assertion so an accidental field addition or type change fails the build instead of silently shipping a breaking change.
• Cross-process compatibility checks: embed the hash in a file header or wire protocol handshake so mismatched producers and consumers reject each other early.
• Cache/index invalidation: key a persisted cache on the signature so rebuilding a type's schema automatically invalidates stale data.

This trait is no-std compatible! The dependency on std and alloc are both controlled by features.

Example

use type_signature::TypeSignature;

#[derive(TypeSignature)]
struct Message {
    id: u64,
    body: String,
}

// Lock in the current schema at compile time. Changing `Message` in a
// breaking way will fail this assertion.
const _: () = assert!(Message::CONST_HASH == 0x7190_e284_5c80_29a5);

MSRV Policy

This crate has a minimum supported Rust version in the Cargo.toml. It may be updated on minor version releases of this crate, but will be at least 2 release cycles old.