refactor(stm): Ensuring type consistency for SNARK circuit - #3071
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Pull request overview
This PR updates the Halo2 STM circuit boundary to better align with STM protocol types by introducing a checked constructor that safely narrows STM u64 parameters into the circuit’s u32 internal representation, and updates golden tests accordingly.
Changes:
- Removed the Halo2-local
LotteryIndexalias and standardized on the crate-levelLotteryIndex(u64). - Added
StmCircuit::try_new(Parameters, merkle_tree_depth)to validateu64 -> u32narrowing at circuit creation time. - Updated golden witness builders and cases to use
LotteryIndex-compatible indices and updated circuit setup to usetry_new.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| mithril-stm/src/circuits/halo2/types.rs | Removes Halo2-local LotteryIndex alias to avoid type divergence from STM domain types. |
| mithril-stm/src/circuits/halo2/circuit.rs | Adds try_new for checked narrowing of STM parameters and updates witness index assignment to use LotteryIndex directly. |
| mithril-stm/src/circuits/halo2/golden/helpers.rs | Updates golden helpers to use LotteryIndex in witness entries and constructs StmCircuit via try_new. |
| mithril-stm/src/circuits/halo2/golden/cases/positive.rs | Adjusts test indices to remain compatible with LotteryIndex/u64-based APIs. |
| mithril-stm/src/circuits/halo2/golden/cases/negative.rs | Adjusts negative test indices to remain compatible with LotteryIndex/u64-based APIs. |
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Content
This PR includes modifications to the creation function of
StmCircuitto ensure that the types received from the STM protocol fit in the types of the circuit.It also includes tests and results on the impact of changing the types within the circuit on the numbers of constraints of the circuit. Those results are added to the SNARK MVP Book.
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Comments
Issue(s)
Closes to #3036