fix unused variable

Author: quaternic

libm/src/math/support/big.rs

@@ -115,12 +115,7 @@ macro_rules! impl_common {
             fn add(self, rhs: Self) -> Self::Output {
                 let (lo, carry) = self.lo.overflowing_add(rhs.lo);
                 let (hi, of) = Int::carrying_add(self.hi, rhs.hi, carry);
-
-                #[cfg(debug_assertions)]
-                if of {
-                    panic!("attempt to add with overflow")
-                }
-
+                debug_assert!(!of, "attempt to add with overflow");
                 Self { lo, hi }
             }
         }
@@ -131,12 +126,7 @@ macro_rules! impl_common {
             fn sub(self, rhs: Self) -> Self::Output {
                 let (lo, borrow) = self.lo.overflowing_sub(rhs.lo);
                 let (hi, of) = Int::borrowing_sub(self.hi, rhs.hi, borrow);
-
-                #[cfg(debug_assertions)]
-                if of {
-                    panic!("attempt to subtract with overflow")
-                }
-
+                debug_assert!(!of, "attempt to subtract with overflow");
                 Self { lo, hi }
             }
         }