use thiserror (#135)

Cargo.toml

@@ -32,6 +32,7 @@ bincode = "1.2.1"
 flate2 = "1.0"
 bitvec = "1.0"
 byteorder = "1.4.3"
+thiserror = "1.0" 
 
 [target.'cfg(any(target_arch = "x86_64", target_arch = "aarch64"))'.dependencies]
 pasta-msm = { version = "0.1.0", package = "lurk-pasta-msm" }

src/errors.rs

@@ -1,31 +1,44 @@
 //! This module defines errors returned by the library.
 use core::fmt::Debug;
+use thiserror::Error;
 
 /// Errors returned by Nova
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq, Error)]
 pub enum NovaError {
   /// returned if the supplied row or col in (row,col,val) tuple is out of range
+  #[error("InvalidIndex")]
   InvalidIndex,
   /// returned if the supplied input is not even-sized
+  #[error("OddInputLength")]
   OddInputLength,
   /// returned if the supplied input is not of the right length
+  #[error("InvalidInputLength")]
   InvalidInputLength,
   /// returned if the supplied witness is not of the right length
+  #[error("InvalidWitnessLength")]
   InvalidWitnessLength,
   /// returned if the supplied witness is not a satisfying witness to a given shape and instance
+  #[error("UnSat")]
   UnSat,
   /// returned when the supplied compressed commitment cannot be decompressed
+  #[error("DecompressionError")]
   DecompressionError,
   /// returned if proof verification fails
+  #[error("ProofVerifyError")]
   ProofVerifyError,
   /// returned if the provided number of steps is zero
+  #[error("InvalidNumSteps")]
   InvalidNumSteps,
   /// returned when an invalid inner product argument is provided
+  #[error("InvalidIPA")]
   InvalidIPA,
   /// returned when an invalid sum-check proof is provided
+  #[error("InvalidSumcheckProof")]
   InvalidSumcheckProof,
   /// returned when the initial input to an incremental computation differs from a previously declared arity
+  #[error("InvalidInitialInputLength")]
   InvalidInitialInputLength,
   /// returned when the step execution produces an output whose length differs from a previously declared arity
+  #[error("InvalidStepOutputLength")]
   InvalidStepOutputLength,
 }