following up on btoi removal

gix-utils/src/btoi.rs

@@ -118,7 +118,7 @@ pub fn to_unsigned_with_radix<I: MinNumTraits>(bytes: &[u8], radix: u32) -> Resu
         return Err(ParseIntegerError { kind: ErrorKind::Empty });
     }
 
-    let mut result = I::zero();
+    let mut result = I::ZERO;
 
     for &digit in bytes {
         let x = match char::from(digit).to_digit(radix).and_then(I::from_u32) {
@@ -236,7 +236,7 @@ pub fn to_signed_with_radix<I: MinNumTraits>(bytes: &[u8], radix: u32) -> Result
         return Err(ParseIntegerError { kind: ErrorKind::Empty });
     }
 
-    let mut result = I::zero();
+    let mut result = I::ZERO;
 
     for &digit in digits {
         let x = match char::from(digit).to_digit(radix).and_then(I::from_u32) {
@@ -269,48 +269,42 @@ pub fn to_signed_with_radix<I: MinNumTraits>(bytes: &[u8], radix: u32) -> Result
 }
 
 /// minimal subset of traits used by [`to_signed_with_radix`] and [`to_unsigned_with_radix`]
-pub trait MinNumTraits: Sized + Copy {
-    ///
-    fn from_u32(n: u32) -> Option<Self>;
-    ///
-    fn zero() -> Self;
-    ///
-    fn checked_mul(self, v: Self) -> Option<Self>;
-    ///
-    fn checked_add(self, v: Self) -> Option<Self>;
-    ///
+pub trait MinNumTraits: Sized + Copy + TryFrom<u32> {
+    /// the 0 value for this type
+    const ZERO: Self;
+    /// convert from a unsinged 32-bit word
+    fn from_u32(n: u32) -> Option<Self> {
+        Self::try_from(n).ok()
+    }
+    /// the checked multiplication operation for this type
+    fn checked_mul(self, rhs: Self) -> Option<Self>;
+    /// the chekced addition operation for this type
+    fn checked_add(self, rhs: Self) -> Option<Self>;
+    /// the checked subtraction operation for this type
     fn checked_sub(self, v: Self) -> Option<Self>;
 }
 
+macro_rules! impl_checked {
+    ($f:ident) => {
+        fn $f(self, rhs: Self) -> Option<Self> {
+            Self::$f(self, rhs)
+        }
+    };
+}
+
 macro_rules! min_num_traits {
-    ($t : ty, from_u32 => $from_u32 : expr) => {
+    ($t:ty) => {
         impl MinNumTraits for $t {
-            fn from_u32(n: u32) -> Option<$t> {
-                #[allow(clippy::redundant_closure_call)]
-                $from_u32(n)
-            }
-
-            fn zero() -> Self {
-                0
-            }
-
-            fn checked_mul(self, v: $t) -> Option<$t> {
-                <$t>::checked_mul(self, v)
-            }
-
-            fn checked_add(self, v: $t) -> Option<$t> {
-                <$t>::checked_add(self, v)
-            }
-
-            fn checked_sub(self, v: $t) -> Option<$t> {
-                <$t>::checked_sub(self, v)
-            }
+            const ZERO: Self = 0;
+            impl_checked!(checked_add);
+            impl_checked!(checked_mul);
+            impl_checked!(checked_sub);
         }
     };
 }
 
-min_num_traits!(i32, from_u32 => |n: u32| n.try_into().ok());
-min_num_traits!(i64, from_u32 => |n: u32| Some(n.into()));
-min_num_traits!(u64, from_u32 => |n: u32| Some(n.into()));
-min_num_traits!(u8, from_u32 => |n: u32| n.try_into().ok());
-min_num_traits!(usize, from_u32 => |n: u32| n.try_into().ok());
+min_num_traits!(i32);
+min_num_traits!(i64);
+min_num_traits!(u64);
+min_num_traits!(u8);
+min_num_traits!(usize);