remove unreachable variant, add comments to snark verification tests

zokrates_core_test/tests/tests/snark/snark_verify_bls12_377_1.zok

@@ -1,5 +1,11 @@
 from "EMBED" import snark_verify_bls12_377
 
+// Verifies a proof with 1 public input (0 inputs + 1 output)
+// Circuit used in this test:
+//
+// def main() -> field:
+//     return 1
+
 def main(private field[1] inputs, private field[8] proof, private field[20] vk) -> bool:
     bool result = snark_verify_bls12_377(inputs, proof, vk)
     return result

zokrates_core_test/tests/tests/snark/snark_verify_bls12_377_2.zok

@@ -1,5 +1,11 @@
 from "EMBED" import snark_verify_bls12_377
 
+// Verifies a proof with 2 public inputs (1 input + 1 output)
+// Circuit used in this test:
+//
+// def main(field a) -> field:
+//     return a * a
+
 def main(private field[2] inputs, private field[8] proof, private field[22] vk) -> bool:
     bool result = snark_verify_bls12_377(inputs, proof, vk)
     return result

zokrates_core_test/tests/tests/snark/snark_verify_bls12_377_5.zok

@@ -1,5 +1,15 @@
 from "EMBED" import snark_verify_bls12_377
 
+// Verifies a proof with 5 public inputs (4 inputs + 1 output)
+// Circuit used in this test:
+//
+// def main(field[4] a) -> field:
+//     field out = 0
+//     for u32 i in 0..4 do
+//         out = out + a[i]
+//     endfor
+//     return out
+
 def main(private field[5] inputs, private field[8] proof, private field[28] vk) -> bool:
     bool result = snark_verify_bls12_377(inputs, proof, vk)
     return result

zokrates_embed/src/ark.rs

@@ -58,7 +58,7 @@ pub fn generate_verify_constraints(
     let cs_sys = ConstraintSystem::<BW6Fr>::new();
     let cs = ConstraintSystemRef::new(cs_sys);
 
-    let mut rng = test_rng();
+    let mut rng = test_rng(); // has a fixed seed
     let circuit = DefaultCircuit { public_input_size };
 
     let (pk, vk) = GM17Snark::circuit_specific_setup(circuit, &mut rng).unwrap();
@@ -161,10 +161,6 @@ pub fn generate_verify_constraints(
             .variable()
             .get_index_unchecked(num_instance_variables)
             .unwrap(),
-        Boolean::Not(x) => x
-            .variable()
-            .get_index_unchecked(num_instance_variables)
-            .unwrap(),
         _ => unreachable!(),
     };