nom::alt_complete

macro_rules! alt_complete {
    ($i:expr, $e:ident | $($rest:tt)*) => { ... };
    ($i:expr, $subrule:ident!( $($args:tt)*) | $($rest:tt)*) => { ... };
    ($i:expr, $subrule:ident!( $($args:tt)* ) => { $gen:expr } | $($rest:tt)+) => { ... };
    ($i:expr, $e:ident => { $gen:expr } | $($rest:tt)*) => { ... };
    ($i:expr, $e:ident => { $gen:expr }) => { ... };
    ($i:expr, $subrule:ident!( $($args:tt)* ) => { $gen:expr }) => { ... };
    ($i:expr, $e:ident) => { ... };
    ($i:expr, $subrule:ident!( $($args:tt)*)) => { ... };
}

This is a combination of the alt! and complete! combinators. Rather than returning Incomplete on partial input, alt_complete! will try the next alternative in the chain. You should use this only if you know you will not receive partial input for the rules you're trying to match (this is almost always the case for parsing programming languages).