Monadic checked arithmetic for Rust

This library provides types wrapping raw numeric types, and tracking possibility of an overflow, enforcing correct handling without possibility of panics or incorrect values (when overflow checks in release build are disabled).

[Checked] is the main type provided by this library.

use overflow_proof::Checked;

let a = Checked::new(2u8);
let b = Checked::new(100u8);

// Aritmetic operations can be chained like with normal types
assert!({ ((a + 2) / 3 + 5) * b + 1}.check().is_none());
assert_eq!(*{ a + 2 + b }.check().expect("overflow"), 104);

use overflow_proof::{Checked, WithDeref};

struct OverflowError;

struct BankAccount {
  balance: Checked<u64>,
}

impl BankAccount {
  fn debit(&mut self, amount: u64) -> Result<(), OverflowError> {
  // Will not compile:
  // Ok(self.balance -= amount)

  // Overflow must be checked:
  Ok(self.balance = {self.balance - amount}.check().ok_or(OverflowError)?)
  }
}