Initial Circom 2 support (#10)

* Import circom-2 test vectors

* Add failing test under feature flag

* Add exceptionHandler

* Add showSharedRWMemory

* Add getFieldNumLen32 and disable getFrLen

* Add getVersion

Also print version, n32

* Add getRawPrime

- Disable getPtrRawPrime
- Write as conditional cfg code blocks

* Refactor cfg code blocks

* Add readSharedRWMemory and get prime from WASM mem

- Add fromArray32 convenience function

* WIP: Debug R1CSfile header

field_size in header is 1, not 32 as expected

Don't see anything recently changed here:
https://github.com/iden3/r1csfile/blob/master/src/r1csfile.js (used by snarkjs)

But this seems new: 0149dc0643/constraint_writers/src/r1cs_writer.rs

* Add CircomVersion struct to Wasm

* XXX: Enum test

* Trait version

* Move traits to Circom, CircomBase, Circom2

* Simplify Wasm struct and remove version

* Feature gate Circom1/Circom2 traits

* Use cfg_if for witness calculation

Make normal dependency

* Fix visibilty for both test paths

* Remove println

Can introduce tracing separately

* refactor

* Make clippy happy with imports, unused variables

tests/groth16.rs

@@ -58,3 +58,35 @@ fn groth16_proof_wrong_input() {
 
     builder.build().unwrap_err();
 }
+
+#[test]
+#[cfg(feature = "circom-2")]
+fn groth16_proof_circom2() -> Result<()> {
+    let cfg = CircomConfig::<Bn254>::new(
+        "./test-vectors/circom2_multiplier2.wasm",
+        "./test-vectors/circom2_multiplier2.r1cs",
+    )?;
+    let mut builder = CircomBuilder::new(cfg);
+    builder.push_input("a", 3);
+    builder.push_input("b", 11);
+
+    // create an empty instance for setting it up
+    let circom = builder.setup();
+
+    let mut rng = thread_rng();
+    let params = generate_random_parameters::<Bn254, _, _>(circom, &mut rng)?;
+
+    let circom = builder.build()?;
+
+    let inputs = circom.get_public_inputs().unwrap();
+
+    let proof = prove(circom, &params, &mut rng)?;
+
+    let pvk = prepare_verifying_key(&params.vk);
+
+    let verified = verify_proof(&pvk, &proof, &inputs)?;
+
+    assert!(verified);
+
+    Ok(())
+}