Macro checked_ops 

macro_rules! checked_ops {
    ($($rest:tt)+) => { ... };
}

Takes an expression and expands it into a “checked” form.

Supported operators are: +, -, *, /, % (binary operators), and as (cast).

Supported operands are: number literals, simple variables (single-token expressions), and pathenthesized expressions.

Examples

assert_eq!(checked_ops!(1 - 2), Some(-1));
assert_eq!(checked_ops!(1u32 - 2), None);
assert_eq!(checked_ops!((1 - 2) as u32), None);
assert_eq!(checked_ops!(1 / 0), None);

Caveats

• Non-single-token operands such as field expressions (struct.attribute), function calls (function()), and paths (std::u32::MAX) are not supported.
• Operators not listed above are not yet supported. These include unary - (negative), <<, and >> (bit shift).
• A long expression causes “recursion limit reached while expanding the macro” error.