Make Field::square take &self and return Self

src/domain.rs

@@ -63,7 +63,7 @@ impl<E: ScalarEngine, G: Group<E>> EvaluationDomain<E, G> {
         // Compute omega, the 2^exp primitive root of unity
         let mut omega = E::Fr::root_of_unity();
         for _ in exp..E::Fr::S {
-            omega.square();
+            omega = omega.square();
         }
 
         // Extend the coeffs vector with zeroes if necessary

src/gadgets/num.rs

@@ -254,8 +254,7 @@ impl<E: ScalarEngine> AllocatedNum<E> {
         let var = cs.alloc(
             || "squared num",
             || {
-                let mut tmp = *self.value.get()?;
-                tmp.square();
+                let tmp = self.value.get()?.square();
 
                 value = Some(tmp);
 

src/groth16/tests/dummy_engine.rs

@@ -140,8 +140,8 @@ impl Field for Fr {
         (self.0).0 == 0
     }
 
-    fn square(&mut self) {
-        self.0 = (self.0 * self.0) % MODULUS_R;
+    fn square(&self) -> Self {
+        Fr((self.0 * self.0) % MODULUS_R)
     }
 
     fn double(&self) -> Self {
@@ -191,22 +191,21 @@ impl SqrtField for Fr {
                 while t != <Fr as Field>::one() {
                     let mut i = 1;
                     {
-                        let mut t2i = t;
-                        t2i.square();
+                        let mut t2i = t.square();
                         loop {
                             if t2i == <Fr as Field>::one() {
                                 break;
                             }
-                            t2i.square();
+                            t2i = t2i.square();
                             i += 1;
                         }
                     }
 
                     for _ in 0..(m - i - 1) {
-                        c.square();
+                        c = c.square();
                     }
                     MulAssign::mul_assign(&mut r, &c);
-                    c.square();
+                    c = c.square();
                     MulAssign::mul_assign(&mut t, &c);
                     m = i;
                 }

tests/mimc.rs

@@ -41,8 +41,7 @@ fn mimc<E: Engine>(mut xl: E::Fr, mut xr: E::Fr, constants: &[E::Fr]) -> E::Fr {
     for i in 0..MIMC_ROUNDS {
         let mut tmp1 = xl;
         tmp1.add_assign(&constants[i]);
-        let mut tmp2 = tmp1;
-        tmp2.square();
+        let mut tmp2 = tmp1.square();
         tmp2.mul_assign(&tmp1);
         tmp2.add_assign(&xr);
         xr = xl;
@@ -88,8 +87,7 @@ impl<'a, E: Engine> Circuit<E> for MiMCDemo<'a, E> {
             // tmp = (xL + Ci)^2
             let tmp_value = xl_value.map(|mut e| {
                 e.add_assign(&self.constants[i]);
-                e.square();
-                e
+                e.square()
             });
             let tmp = cs.alloc(
                 || "tmp",