Macro eval_break

macro_rules! eval_break {
    ($value:expr, $ctxt:expr) => { ... };
}

Helper macro to call Eval::eval, then check if the loop should be broken. Errors will also be propogated automatically with the ? operator.

The return type of this macro is Value. It can also diverge if evaluation fails, or if break_loop is true, with type Result<Value, Error>.