Macro try_or_coerce

macro_rules! try_or_coerce {
    ($op: expr, $to: ident) => { ... };
}

Convert a TransactionClosureResult<T, E_A> to TransactionClosureResult<T, E_B>.

This macro is used to cleanly write transactions where multiple kind of errors are possible during execution. The macro will not fail as long as the specified target error $to implements From<E>, E being the error possibly returned by $op. It expands to:

$op.map_err(|e| match e {
        fast_stm::TransactionError::Abort(e) => fast_stm::TransactionError::Abort($to::from(e)),
        fast_stm::TransactionError::Stm(e) => fast_stm::TransactionError::Stm(e),
    })?

Example

struct Error1;
struct Error2;

impl From<Error1> for Error2 {
    fn from(e: Error1) -> Self {
        Error2
    }
}

fn op1(trans: &mut Transaction) -> TransactionClosureResult<(), Error1> {
    // ...
    Ok(())
}

fn op2(trans: &mut Transaction) -> TransactionClosureResult<(), Error2> {
    // ...
    Ok(())
}

let res: Result<(), Error2> = atomically_with_err(|trans| {
    try_or_coerce!(op1(trans), Error2);
    op2(trans)?;   
    Ok(())
});