Place halo2_proofs::plonk::BatchVerifier behind a (default enabled) crate feature called batch.

halo2_proofs/CHANGELOG.md

@@ -43,7 +43,8 @@ All APIs that represented witnessed values as `Option<V>` now represent them as
     - `RegionLayouter::assign_advice_from_instance`
 - `halo2_proofs::plonk::BatchVerifier` has been rewritten. It is no longer a
   verification strategy to be used with `verify_proof`, but instead manages the
-  entire batch verification process.
+  entire batch verification process. The `batch` crate feature (enabled by
+  default) must be enabled to use the batch verifier.
 
 ## [0.1.0] - 2022-05-10
 ### Added

halo2_proofs/Cargo.toml

@@ -68,9 +68,11 @@ rand_core = { version = "0.6", default-features = false, features = ["getrandom"
 getrandom = { version = "0.2", features = ["js"] }
 
 [features]
+default = ["batch"]
 dev-graph = ["plotters", "tabbycat"]
 gadget-traces = ["backtrace"]
 sanity-checks = []
+batch = ["rand_core/getrandom"]
 
 [lib]
 bench = false

halo2_proofs/src/plonk/verifier.rs

@@ -14,7 +14,9 @@ use crate::poly::{
 };
 use crate::transcript::{read_n_points, read_n_scalars, EncodedChallenge, TranscriptRead};
 
+#[cfg(feature = "batch")]
 mod batch;
+#[cfg(feature = "batch")]
 pub use batch::BatchVerifier;
 
 /// Trait representing a strategy for verifying Halo 2 proofs.

halo2_proofs/src/plonk/verifier/batch.rs

@@ -47,7 +47,8 @@ struct BatchItem<C: CurveAffine> {
     proof: Vec<u8>,
 }
 
-/// A verifier that checks multiple proofs in a batch.
+/// A verifier that checks multiple proofs in a batch. **This requires the
+/// `batch` crate feature to be enabled.**
 #[derive(Debug, Default)]
 pub struct BatchVerifier<C: CurveAffine> {
     items: Vec<BatchItem<C>>,