fp: use arkworks for u64_backend

Author: redshiftzero

src/fields/fp.rs

@@ -7,13 +7,16 @@ use crate::EncodingError;
 pub mod arkworks;
 mod ops;
 mod u32;
+
+// The u64 backend requires arkworks
+#[cfg(feature = "arkworks")]
 mod u64;
 
 cfg_if! {
-    if #[cfg(feature = "u32_backend")] {
-        pub type Fp = u32::Fp;
-    } else {
+    if #[cfg(feature = "arkworks")] {
         pub type Fp = u64::Fp;
+    } else {
+        pub type Fp = u32::Fp;
     }
 }
 

src/fields/fp/arkworks.rs

@@ -658,9 +658,7 @@ mod tests {
     #[test]
     fn test_minus_one_squared() {
         let minus_one = Fp::zero() - Fp::one();
-        assert_eq!(Fp::one(), Fp::ONE);
-
-        //assert_eq!(minus_one.square(), Fp::ONE);
+        assert_eq!(minus_one.square(), Fp::ONE);
     }
 
     #[test]

src/fields/fp/u64.rs

@@ -1,4 +1,3 @@
-pub mod fiat;
 pub mod wrapper;
 
 pub use wrapper::Fp;