Macro try_blocks::try_block

macro_rules! try_block {
    { $($token:tt)* } => { ... };
}

Macro for the recieving end of a ? operation. Right now, type inference is quite finicky so you usually have to declare a concrete type somewhere.

// Note: this fails without explicitly specifying the error type.
let y: Result<_, std::num::ParseIntError> = try_block! {
    "1".parse::<i32>()? + "2".parse::<i32>()?
};

Alternative

The only other way to emulate try blocks is with closures, which is very ugly.

Before:

let result: Result<T, E> = (|| {
   let a = do_one(x)?;
   let b = do_two(a)?;
   Ok(b)
})();

After:

let result: Result<T, E> = try_block! {
   let a = do_one(x)?;
   let b = do_two(a)?;
   b
};