feat: [wip] add support for uniffi-rs foreign bindings #482
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curious to hear high level thoughts around potential approaches for this |
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Can you provide quick swift code snippets showing what developer experience would be like with each approach? I'm concerned about the inability to push generics through the interface requiring declaring a separate type for each variant. if we home those types here, users are limited in what types they can use, and if homed elsewhere, there may be multiple incompatible |
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Motivation
Motivation for this PR is allowing
UInts to be lowered & lifted to foreign bindings (e.g. Swift & Kotlin) through Mozilla's https://github.com/mozilla/uniffi-rs. Rust libraries relying on uniffi, would be able to work withUInts in foreign code. For us, we would rely on this for https://github.com/worldcoin/walletkit & https://github.com/worldcoin/bedrockSolution
There are two conceptual solutions.
UInts to foreign code. A U256 for example would be lowered as a struct with 4xu64, not to dissimilar to the mainUInttype. This is the most Rust-compatible, no changes are needed on the Rust side for downstream crates. The trade-off is that on the foreign side, no methods can be exposed for the type. Everything would have to be exposed as first-level functions (and potentially patched on the foreign side with extensions).UIntwhich can be extended to expose additional functionality to foreign code (see 4ee8e1c#diff-335af168ef5906f688caca114e10649fb5ccb74611bce562a82533c4324cb043). Trade-off is it'll require conversions in the Rust side.In any case, uniffi does not support exposing generics (the
BITS/LIMBS), so explicit declarations for aliases will have to be used. An alternative approach would be introducing a new type, but I don't think that's the best approach.PR Checklist