remove unnecessary try_opt for operations that cannot fail

Author: tspiteri

library/core/src/num/int_macros.rs

@@ -2166,15 +2166,17 @@ macro_rules! int_impl {
 
             let r = try_opt!(self.checked_rem(rhs));
             let m = if (r > 0 && rhs < 0) || (r < 0 && rhs > 0) {
-                try_opt!(r.checked_add(rhs))
+                // r + rhs cannot overflow because they have opposite signs
+                r + rhs
             } else {
                 r
             };
 
             if m == 0 {
                 Some(self)
             } else {
-                self.checked_add(try_opt!(rhs.checked_sub(m)))
+                // rhs - m cannot overflow because m has the same sign as rhs
+                self.checked_add(rhs - m)
             }
         }
 

library/core/src/num/uint_macros.rs

@@ -2119,7 +2119,8 @@ macro_rules! uint_impl {
         pub const fn checked_next_multiple_of(self, rhs: Self) -> Option<Self> {
             match try_opt!(self.checked_rem(rhs)) {
                 0 => Some(self),
-                r => self.checked_add(try_opt!(rhs.checked_sub(r)))
+                // rhs - r cannot overflow because r is smaller than rhs
+                r => self.checked_add(rhs - r)
             }
         }