avoid calls to pp.digest in prove methods (#320)

* avoid calls to pp.digest in prove methods

* remove unused

* address clippy

src/gadgets/nonnative/mod.rs

@@ -6,16 +6,12 @@ use ff::PrimeField;
 
 trait OptionExt<T> {
   fn grab(&self) -> Result<&T, SynthesisError>;
-  fn grab_mut(&mut self) -> Result<&mut T, SynthesisError>;
 }
 
 impl<T> OptionExt<T> for Option<T> {
   fn grab(&self) -> Result<&T, SynthesisError> {
     self.as_ref().ok_or(SynthesisError::AssignmentMissing)
   }
-  fn grab_mut(&mut self) -> Result<&mut T, SynthesisError> {
-    self.as_mut().ok_or(SynthesisError::AssignmentMissing)
-  }
 }
 
 trait BitAccess {

src/lib.rs

@@ -185,7 +185,7 @@ where
       return Err(NovaError::InvalidStepCircuitIO);
     }
 
-    Ok(PublicParams {
+    let pp = PublicParams {
       F_arity_primary,
       F_arity_secondary,
       ro_consts_primary,
@@ -200,7 +200,12 @@ where
       augmented_circuit_params_secondary,
       digest: OnceCell::new(),
       _p: Default::default(),
-    })
+    };
+
+    // call pp.digest() so the digest is computed here rather than in RecursiveSNARK methods
+    let _ = pp.digest();
+
+    Ok(pp)
   }
 
   /// Retrieve the digest of the public parameters.

src/provider/hyperkzg.rs

@@ -765,7 +765,8 @@ mod tests {
 
     // Change the proof and expect verification to fail
     let mut bad_proof = proof.clone();
-    bad_proof.v[0] = bad_proof.v[1].clone();
+    let v1 = bad_proof.v[1].clone();
+    bad_proof.v[0].clone_from(&v1);
     let mut verifier_transcript2 = Keccak256Transcript::new(b"TestEval");
     assert!(EvaluationEngine::verify(
       &vk,
@@ -808,7 +809,8 @@ mod tests {
 
       // Change the proof and expect verification to fail
       let mut bad_proof = proof.clone();
-      bad_proof.v[0] = bad_proof.v[1].clone();
+      let v1 = bad_proof.v[1].clone();
+      bad_proof.v[0].clone_from(&v1);
       let mut verifier_tr2 = Keccak256Transcript::new(b"TestEval");
       assert!(
         EvaluationEngine::verify(&vk, &mut verifier_tr2, &C, &point, &eval, &bad_proof).is_err()

src/r1cs/mod.rs

@@ -480,7 +480,8 @@ impl<E: Engine> RelaxedR1CSInstance<E> {
     let mut r_instance = RelaxedR1CSInstance::default(ck, S);
     r_instance.comm_W = instance.comm_W;
     r_instance.u = E::Scalar::ONE;
-    r_instance.X = instance.X.clone();
+    r_instance.X.clone_from(&instance.X);
+
     r_instance
   }
 

src/spartan/direct.rs

@@ -277,7 +277,7 @@ mod tests {
       assert!(res.is_ok());
 
       // set input to the next step
-      z_i = z_i_plus_one.clone();
+      z_i.clone_from(&z_i_plus_one);
     }
 
     // sanity: check the claimed output with a direct computation of the same

src/spartan/math.rs

@@ -1,23 +1,8 @@
 pub trait Math {
-  fn pow2(self) -> usize;
-  fn get_bits(self, num_bits: usize) -> Vec<bool>;
   fn log_2(self) -> usize;
 }
 
 impl Math for usize {
-  #[inline]
-  fn pow2(self) -> usize {
-    let base: usize = 2;
-    base.pow(self as u32)
-  }
-
-  /// Returns the `num_bits` from n in a canonical order
-  fn get_bits(self, num_bits: usize) -> Vec<bool> {
-    (0..num_bits)
-      .map(|shift_amount| ((self & (1 << (num_bits - shift_amount - 1))) > 0))
-      .collect::<Vec<bool>>()
-  }
-
   fn log_2(self) -> usize {
     assert_ne!(self, 0);