Remove impl_isqrt macro

The implementation can now just use a normal generic impl. Note that
this is tecnically a minor breaking change, as if a user has both:
  - A custom num_traits::PrimInt impl
  - A custom IntegerSquareRoot impl

Their code will no longer compile

Signed-off-by: Joe Richey <joerichey@google.com>

src/lib.rs

@@ -44,49 +44,39 @@ pub trait IntegerSquareRoot {
         Self: Sized;
 }
 
-#[inline(always)]
-fn integer_sqrt_impl<T: num_traits::PrimInt>(mut n: T) -> Option<T> {
-    use core::cmp::Ordering;
-    match n.cmp(&T::zero()) {
-        // Hopefully this will be stripped for unsigned numbers (impossible condition)
-        Ordering::Less => return None,
-        Ordering::Equal => return Some(T::zero()),
-        _ => {}
-    }
-
-    // Compute bit, the largest power of 4 <= n
-    let max_shift: u32 = T::zero().leading_zeros() - 1;
-    let shift: u32 = (max_shift - n.leading_zeros()) & !1;
-    let mut bit = T::one().unsigned_shl(shift);
-
-    // Algorithm based on the implementation in:
-    // https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Binary_numeral_system_(base_2)
-    // Note that result/bit are logically unsigned (even if T is signed).
-    let mut result = T::zero();
-    while bit != T::zero() {
-        if n >= (result + bit) {
-            n = n - (result + bit);
-            result = result.unsigned_shr(1) + bit;
-        } else {
-            result = result.unsigned_shr(1);
+impl<T: num_traits::PrimInt> IntegerSquareRoot for T {
+    fn integer_sqrt_checked(&self) -> Option<Self> {
+        use core::cmp::Ordering;
+        match self.cmp(&T::zero()) {
+            // Hopefully this will be stripped for unsigned numbers (impossible condition)
+            Ordering::Less => return None,
+            Ordering::Equal => return Some(T::zero()),
+            _ => {}
         }
-        bit = bit.unsigned_shr(2);
-    }
-    Some(result)
-}
 
-macro_rules! impl_isqrt {
-    ($($t:ty)*) => { $(
-        impl IntegerSquareRoot for $t {
-            fn integer_sqrt_checked(&self) -> Option<Self> {
-                integer_sqrt_impl(*self)
+        // Compute bit, the largest power of 4 <= n
+        let max_shift: u32 = T::zero().leading_zeros() - 1;
+        let shift: u32 = (max_shift - self.leading_zeros()) & !1;
+        let mut bit = T::one().unsigned_shl(shift);
+
+        // Algorithm based on the implementation in:
+        // https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Binary_numeral_system_(base_2)
+        // Note that result/bit are logically unsigned (even if T is signed).
+        let mut n = *self;
+        let mut result = T::zero();
+        while bit != T::zero() {
+            if n >= (result + bit) {
+                n = n - (result + bit);
+                result = result.unsigned_shr(1) + bit;
+            } else {
+                result = result.unsigned_shr(1);
             }
+            bit = bit.unsigned_shr(2);
         }
-    )* };
+        Some(result)
+    }
 }
 
-impl_isqrt!(usize u128 u64 u32 u16 u8 isize i128 i64 i32 i16 i8);
-
 #[cfg(test)]
 mod tests {
     use super::IntegerSquareRoot;