impl TryInto<Goldilocks> for Ext2/3

src/fp2.rs

@@ -383,3 +383,17 @@ impl GoldilocksExt2 {
         Self(res)
     }
 }
+
+impl TryInto<Goldilocks> for GoldilocksExt2 {
+    /// The type returned in the event of a conversion error.
+    type Error = &'static str;
+
+    /// Performs the conversion.
+    fn try_into(self) -> Result<Goldilocks, Self::Error> {
+        if self.0[1].is_zero_vartime() {
+            Ok(self.0[0])
+        } else {
+            Err("extension field is not zero")
+        }
+    }
+}

src/fp3.rs

@@ -369,3 +369,17 @@ impl FromUniformBytes<64> for GoldilocksExt3 {
         ])
     }
 }
+
+impl TryInto<Goldilocks> for GoldilocksExt3 {
+    /// The type returned in the event of a conversion error.
+    type Error = &'static str;
+
+    /// Performs the conversion.
+    fn try_into(self) -> Result<Goldilocks, Self::Error> {
+        if self.0[1].is_zero_vartime() && self.0[2].is_zero_vartime() {
+            Ok(self.0[0])
+        } else {
+            Err("extension field is not zero")
+        }
+    }
+}

src/tests.rs

@@ -11,7 +11,6 @@ use rand_xorshift::XorShiftRng;
 
 use crate::SmallField;
 
-
 pub fn random_small_field_tests<F: SmallField>(type_name: String) {
     let mut rng = XorShiftRng::from_seed([
         0x59, 0x62, 0xbe, 0x5d, 0x76, 0x3d, 0x31, 0x8d, 0x17, 0xdb, 0x37, 0x32, 0x54, 0x06, 0xbc,
@@ -41,7 +40,6 @@ pub fn random_small_field_tests<F: SmallField>(type_name: String) {
         assert_eq!(t1, t2);
     }
     end_timer!(start);
-
 }
 
 pub fn random_field_tests<F: Field>(type_name: String) {