reverse condition in uN::checked_sub

Author: ivan-shrimp

Diff for: core/src/num/uint_macros.rs

@@ -584,11 +584,11 @@ macro_rules! uint_impl {
             // Thus, rather than using `overflowing_sub` that produces a wrapping
             // subtraction, check it ourself so we can use an unchecked one.
 
-            if self >= rhs {
+            if self < rhs {
+                None
+            } else {
                 // SAFETY: just checked this can't overflow
                 Some(unsafe { intrinsics::unchecked_sub(self, rhs) })
-            } else {
-                None
             }
         }