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)
  }
  }