synom/src/lib.rs

// Adapted from nom <https://github.com/Geal/nom> by removing the
// IResult::Incomplete variant, which we don't use and which unfortunately more
// than doubles the compilation time.

extern crate unicode_xid;

pub mod space;

#[doc(hidden)]
pub mod helper;

/// The result of a parser.
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum IResult<I, O> {
    /// Parsing succeeded. The first field contains the rest of the unparsed
    /// data and the second field contains the parse result.
    Done(I, O),
    /// Parsing failed.
    Error,
}

impl<'a, O> IResult<&'a str, O> {
    /// Unwraps the result, asserting the the parse is complete. Panics with a
    /// message based on the given string if the parse failed or is incomplete.
    pub fn expect(self, name: &str) -> O {
        match self {
            IResult::Done(mut rest, o) => {
                rest = space::skip_whitespace(rest);
                if rest.is_empty() {
                    o
                } else {
                    panic!("unparsed tokens after {}: {:?}", name, rest)
                }
            }
            IResult::Error => panic!("failed to parse {}", name),
        }
    }
}

/// Define a function from a parser combination.
///
/// - **Syntax:** `named!(NAME -> TYPE, THING)`
#[macro_export]
macro_rules! named {
    ($name:ident -> $o:ty, $submac:ident!( $($args:tt)* )) => {
        fn $name(i: &str) -> $crate::IResult<&str, $o> {
            $submac!(i, $($args)*)
        }
    };

    (pub $name:ident -> $o:ty, $submac:ident!( $($args:tt)* )) => {
        pub fn $name(i: &str) -> $crate::IResult<&str, $o> {
            $submac!(i, $($args)*)
        }
    };
}

/// Invoke the function with the passed in arguments as a parser.
///
/// - **Syntax:** `call!(FUNCTION, ARGS...)`
/// - **Output:** The result of invoking the function `FUNCTION`
///
/// ```rust
/// #[macro_use] extern crate synom;
///
/// use synom::IResult;
///
/// fn parse_char(input: &str, ch: char) -> IResult<&str, char> {
///     if input.starts_with(ch) {
///         IResult::Done(&input[ch.len_utf8()..], ch)
///     } else {
///         IResult::Error
///     }
/// }
///
/// named!(an_a -> char, call!(parse_char, 'a'));
///
/// fn main() {
///     let input = "a";
///
///     let parsed = an_a(input).expect("an a");
///
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! call {
    ($i:expr, $fun:expr $(, $args:expr)*) => {
        $fun($i $(, $args)*)
    };
}

/// Perform a transformation on the result of a parser.
///
/// - **Syntax:** `map!(THING, TRANSFORM)`
/// - **Output:** `THING` after being transformed by `TRANSFORM`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::{Item, Ident};
/// use syn::parse::item;
///
/// fn get_item_ident(item: Item) -> Ident {
///     item.ident
/// }
///
/// named!(item_ident -> Ident, map!(item, get_item_ident));
///
/// fn main() {
///     let input = "fn foo() {}";
///
///     let parsed = item_ident(input).expect("item identifier");
///
///     assert_eq!(parsed.as_ref(), "foo");
/// }
/// ```
#[macro_export]
macro_rules! map {
    ($i:expr, $submac:ident!( $($args:tt)* ), $g:expr) => {
        map_impl!($i, $submac!($($args)*), call!($g))
    };

    ($i:expr, $f:expr, $g:expr) => {
        map_impl!($i, call!($f), call!($g))
    };
}

/// Internal parser, do not use directly
#[doc(hidden)]
#[macro_export]
macro_rules! map_impl {
    ($i:expr, $submac:ident!( $($args:tt)* ), $submac2:ident!( $($args2:tt)* )) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) => {
                $crate::IResult::Done(i, $submac2!(o, $($args2)*))
            }
        }
    };
}

/// Parses successfully if the passed-in parser fails to parse.
///
/// - **Syntax:** `not!(THING)`
/// - **Output:** `""`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::parse::expr;
///
/// // Parse not an expression
/// named!(not_an_expr -> &'static str, not!(call!(expr)));
///
/// fn main() {
///     let input = "";
///
///     let parsed = not_an_expr(input).expect("not an expr");
///     assert_eq!(parsed, "");
/// }
/// ```
#[macro_export]
macro_rules! not {
    ($i:expr, $submac:ident!( $($args:tt)* )) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Done(_, _) => $crate::IResult::Error,
            $crate::IResult::Error => $crate::IResult::Done($i, ""),
        }
    };
}

// This is actually nom's cond_with_error.
/// Conditionally execute the passed-in parser.
///
/// - **Syntax:** `cond!(CONDITION, PARSER)`
/// - **Output:** `Option<PARSER>`
///
/// ```rust
/// #[macro_use] extern crate synom;
///
/// named!(maybe_bang_bang -> bool,
///     do_parse!(
///         bang: option!(punct!("!")) >>
///         cond!(bang.is_some(), punct!("!")) >>
///         (bang.is_some())));
///
/// fn main() {
///     let input = "";
///     let parsed = maybe_bang_bang(input).expect("not bang bang");
///     assert_eq!(parsed, false);
///
///     let input = "!!";
///     let parsed = maybe_bang_bang(input).expect("yes bang bang");
///     assert_eq!(parsed, true);
/// }
/// ```
#[macro_export]
macro_rules! cond {
    ($i:expr, $cond:expr, $submac:ident!( $($args:tt)* )) => {
        if $cond {
            match $submac!($i, $($args)*) {
                $crate::IResult::Done(i, o) => $crate::IResult::Done(i, ::std::option::Option::Some(o)),
                $crate::IResult::Error => $crate::IResult::Error,
            }
        } else {
            $crate::IResult::Done($i, ::std::option::Option::None)
        }
    };

    ($i:expr, $cond:expr, $f:expr) => {
        cond!($i, $cond, call!($f))
    };
}

/// Fails with an error if CONDITION is not true. Otherwise parses PARSER
///
/// - **Syntax:** `cond_reduce!(CONDITION, PARSER)`
/// - **Output:** `PARSER`
///
/// ```rust
/// #[macro_use] extern crate synom;
///
/// named!(maybe_bang_bang -> bool,
///     do_parse!(
///         bang: option!(punct!("!")) >>
///         cond!(bang.is_some(), punct!("!")) >>
///         (bang.is_some())));
///
/// fn main() {
///     let input = "!!";
///     let parsed = maybe_bang_bang(input).expect("yes bang bang");
///     assert_eq!(parsed, true);
/// }
/// ```
#[macro_export]
macro_rules! cond_reduce {
    ($i:expr, $cond:expr, $submac:ident!( $($args:tt)* )) => {
        if $cond {
            $submac!($i, $($args)*)
        } else {
            $crate::IResult::Error
        }
    };

    ($i:expr, $cond:expr, $f:expr) => {
        cond_reduce!($i, $cond, call!($f))
    };
}

/// Value preceded by another macro
///
/// - **Syntax:** `preceded!(OPEN, THING)`
/// - **Output:** `THING`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Expr;
/// use syn::parse::expr;
///
/// // An expression preceded by ##.
/// named!(pound_pound_expr -> Expr,
///     preceded!(
///         punct!("##"),
///         expr));
///
/// fn main() {
///     let input = "## 1 + 1";
///
///     let parsed = pound_pound_expr(input).expect("pound pound expr");
///
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! preceded {
    ($i:expr, $submac:ident!( $($args:tt)* ), $submac2:ident!( $($args2:tt)* )) => {
        match tuple!($i, $submac!($($args)*), $submac2!($($args2)*)) {
            $crate::IResult::Done(remaining, (_, o)) => $crate::IResult::Done(remaining, o),
            $crate::IResult::Error => $crate::IResult::Error,
        }
    };

    ($i:expr, $submac:ident!( $($args:tt)* ), $g:expr) => {
        preceded!($i, $submac!($($args)*), call!($g))
    };

    ($i:expr, $f:expr, $submac:ident!( $($args:tt)* )) => {
        preceded!($i, call!($f), $submac!($($args)*))
    };

    ($i:expr, $f:expr, $g:expr) => {
        preceded!($i, call!($f), call!($g))
    };
}

/// Value followed by a terminator.
///
/// - **Syntax:** `terminated!(THING, CLOSE)`
/// - **Output:** `THING`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Expr;
/// use syn::parse::expr;
///
/// // An expression terminated by ##.
/// named!(expr_pound_pound -> Expr,
///     terminated!(
///         expr,
///         punct!("##")));
///
/// fn main() {
///     let input = "1 + 1 ##";
///
///     let parsed = expr_pound_pound(input).expect("expr pound pound");
///
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! terminated {
    ($i:expr, $submac:ident!( $($args:tt)* ), $submac2:ident!( $($args2:tt)* )) => {
        match tuple!($i, $submac!($($args)*), $submac2!($($args2)*)) {
            $crate::IResult::Done(remaining, (o, _)) => $crate::IResult::Done(remaining, o),
            $crate::IResult::Error => $crate::IResult::Error,
        }
    };

    ($i:expr, $submac:ident!( $($args:tt)* ), $g:expr) => {
        terminated!($i, $submac!($($args)*), call!($g))
    };

    ($i:expr, $f:expr, $submac:ident!( $($args:tt)* )) => {
        terminated!($i, call!($f), $submac!($($args)*))
    };

    ($i:expr, $f:expr, $g:expr) => {
        terminated!($i, call!($f), call!($g))
    };
}

/// A value repeated 0 or more times.
///
/// - **Syntax:** `many0!(THING)`
/// - **Output:** `Vec<THING>`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Item;
/// use syn::parse::item;
///
/// named!(items -> Vec<Item>, many0!(item));
///
/// fn main() {
///     let input = "fn a() {} fn b() {}";
///
///     let parsed = items(input).expect("items");
///
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! many0 {
    ($i:expr, $submac:ident!( $($args:tt)* )) => {{
        let ret;
        let mut res   = ::std::vec::Vec::new();
        let mut input = $i;

        loop {
            if input.is_empty() {
                ret = $crate::IResult::Done(input, res);
                break;
            }

            match $submac!(input, $($args)*) {
                $crate::IResult::Error => {
                    ret = $crate::IResult::Done(input, res);
                    break;
                }
                $crate::IResult::Done(i, o) => {
                    // loop trip must always consume (otherwise infinite loops)
                    if i.len() == input.len() {
                        ret = $crate::IResult::Error;
                        break;
                    }

                    res.push(o);
                    input = i;
                }
            }
        }

        ret
    }};

    ($i:expr, $f:expr) => {
        $crate::many0($i, $f)
    };
}

// Not public API.
#[doc(hidden)]
pub fn many0<'a, T>(mut input: &'a str,
                    f: fn(&'a str) -> IResult<&'a str, T>)
                    -> IResult<&'a str, Vec<T>> {
    let mut res = Vec::new();

    loop {
        if input.is_empty() {
            return IResult::Done(input, res);
        }

        match f(input) {
            IResult::Error => {
                return IResult::Done(input, res);
            }
            IResult::Done(i, o) => {
                // loop trip must always consume (otherwise infinite loops)
                if i.len() == input.len() {
                    return IResult::Error;
                }

                res.push(o);
                input = i;
            }
        }
    }
}

/// look for a value without consuming it.
///
/// - **Syntax:** `peek!(THING)`
/// - **Output:** `Vec<THING>`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Ident;
/// use syn::parse::{ident, expr};
///
/// named!(ident_expr -> Ident,
///     do_parse!(
///         i: peek!(call!(ident)) >>
///         expr >>
///         (i)));
///
/// fn main() {
///     let input = "apple";
///
///     let parsed = ident_expr(input).expect("ident");
///
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! peek {
    ($i:expr, $submac:ident!( $($args:tt)* )) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Done(_, o) => $crate::IResult::Done($i, o),
            $crate::IResult::Error => $crate::IResult::Error,
        }
    };
}

#[macro_export]
macro_rules! take_while1 {
    ($input:expr, $submac:ident!( $($args:tt)* )) => {{
        let mut offset = $input.len();
        for (o, c) in $input.char_indices() {
            if !$submac!(c, $($args)*) {
                offset = o;
                break;
            }
        }
        if offset == 0 {
            $crate::IResult::Error
        } else if offset < $input.len() {
            $crate::IResult::Done(&$input[offset..], &$input[..offset])
        } else {
            $crate::IResult::Done("", $input)
        }
    }};

    ($input:expr, $f:expr) => {
        take_while1!($input, call!($f));
    };
}

#[macro_export]
macro_rules! take_until {
    ($input:expr, $substr:expr) => {{
        if $substr.len() > $input.len() {
            $crate::IResult::Error
        } else {
            let substr_vec: Vec<char> = $substr.chars().collect();
            let mut window: Vec<char> = vec![];
            let mut offset = $input.len();
            let mut parsed = false;
            for (o, c) in $input.char_indices() {
                window.push(c);
                if window.len() > substr_vec.len() {
                    window.remove(0);
                }
                if window == substr_vec {
                    parsed = true;
                    window.pop();
                    let window_len: usize = window.iter()
                        .map(|x| x.len_utf8())
                        .fold(0, |x, y| x + y);
                    offset = o - window_len;
                    break;
                }
            }
            if parsed {
                $crate::IResult::Done(&$input[offset..], &$input[..offset])
            } else {
                $crate::IResult::Error
            }
        }
    }};
}

#[macro_export]
macro_rules! tag {
    ($i:expr, $tag: expr) => {
        if $i.starts_with($tag) {
            $crate::IResult::Done(&$i[$tag.len()..], &$i[0..$tag.len()])
        } else {
            $crate::IResult::Error
        }
    };
}

#[macro_export]
macro_rules! switch {
    ($i:expr, $submac:ident!( $($args:tt)* ), $($p:pat => $subrule:ident!( $($args2:tt)* ))|* ) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) => match o {
                $(
                    $p => $subrule!(i, $($args2)*),
                )*
                _ => $crate::IResult::Error,
            }
        }
    };
}

#[macro_export]
macro_rules! value {
    ($i:expr, $res:expr) => {
        $crate::IResult::Done($i, $res)
    };
}

/// Value surrounded by a pair of delimiters.
///
/// - **Syntax:** `delimited!(OPEN, THING, CLOSE)`
/// - **Output:** `THING`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Expr;
/// use syn::parse::expr;
///
/// // An expression surrounded by [[ ... ]].
/// named!(double_bracket_expr -> Expr,
///     delimited!(
///         punct!("[["),
///         expr,
///         punct!("]]")));
///
/// fn main() {
///     let input = "[[ 1 + 1 ]]";
///
///     let parsed = double_bracket_expr(input).expect("double bracket expr");
///
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! delimited {
    ($i:expr, $submac:ident!( $($args:tt)* ), $($rest:tt)+) => {
        match tuple_parser!($i, (), $submac!($($args)*), $($rest)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i1, (_, o, _)) => $crate::IResult::Done(i1, o)
        }
    };

    ($i:expr, $f:expr, $($rest:tt)+) => {
        delimited!($i, call!($f), $($rest)*)
    };
}

/// One or more of something separated by some separator.
///
/// - **Syntax:** `separated_nonempty_list!(SEPARATOR, THING)`
/// - **Output:** `Vec<THING>`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Ty;
/// use syn::parse::ty;
///
/// // One or more Rust types separated by commas.
/// named!(comma_separated_types -> Vec<Ty>,
///     separated_nonempty_list!(
///         punct!(","),
///         ty));
///
/// fn main() {
///     let input = "&str, Map<K, V>, String";
///
///     let parsed = comma_separated_types(input).expect("comma-separated types");
///
///     assert_eq!(parsed.len(), 3);
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! separated_nonempty_list {
    ($i:expr, $sep:ident!( $($args:tt)* ), $submac:ident!( $($args2:tt)* )) => {{
        let mut res   = ::std::vec::Vec::new();
        let mut input = $i;

        // get the first element
        match $submac!(input, $($args2)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) => {
                if i.len() == input.len() {
                    $crate::IResult::Error
                } else {
                    res.push(o);
                    input = i;

                    while let $crate::IResult::Done(i2, _) = $sep!(input, $($args)*) {
                        if i2.len() == input.len() {
                            break;
                        }

                        if let $crate::IResult::Done(i3, o3) = $submac!(i2, $($args2)*) {
                            if i3.len() == i2.len() {
                                break;
                            }
                            res.push(o3);
                            input = i3;
                        } else {
                            break;
                        }
                    }
                    $crate::IResult::Done(input, res)
                }
            }
        }
    }};

    ($i:expr, $submac:ident!( $($args:tt)* ), $g:expr) => {
        separated_nonempty_list!($i, $submac!($($args)*), call!($g))
    };

    ($i:expr, $f:expr, $submac:ident!( $($args:tt)* )) => {
        separated_nonempty_list!($i, call!($f), $submac!($($args)*))
    };

    ($i:expr, $f:expr, $g:expr) => {
        separated_nonempty_list!($i, call!($f), call!($g))
    };
}

/// Run a series of parsers, and produce all of the results in a tuple.
///
/// - **Syntax:** `tuple!(THING1, THING2, ...)`
/// - **Output:** `(THING1, THING2, ...)`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Ty;
/// use syn::parse::ty;
///
/// named!(two_types -> (Ty, Ty), tuple!(ty, ty));
///
/// fn main() {
///     let input = "&str Map<K, V>";
///
///     let parsed = two_types(input).expect("two_types");
///
///     println!("{:?}", parsed);
/// }
/// ```
#[macro_export]
macro_rules! tuple {
    ($i:expr, $($rest:tt)*) => {
        tuple_parser!($i, (), $($rest)*)
    };
}

/// Internal parser, do not use directly
#[doc(hidden)]
#[macro_export]
macro_rules! tuple_parser {
    ($i:expr, ($($parsed:tt),*), $e:ident, $($rest:tt)*) => {
        tuple_parser!($i, ($($parsed),*), call!($e), $($rest)*)
    };

    ($i:expr, (), $submac:ident!( $($args:tt)* ), $($rest:tt)*) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) =>
                tuple_parser!(i, (o), $($rest)*),
        }
    };

    ($i:expr, ($($parsed:tt)*), $submac:ident!( $($args:tt)* ), $($rest:tt)*) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) =>
                tuple_parser!(i, ($($parsed)* , o), $($rest)*),
        }
    };

    ($i:expr, ($($parsed:tt),*), $e:ident) => {
        tuple_parser!($i, ($($parsed),*), call!($e))
    };

    ($i:expr, (), $submac:ident!( $($args:tt)* )) => {
        $submac!($i, $($args)*)
    };

    ($i:expr, ($($parsed:expr),*), $submac:ident!( $($args:tt)* )) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) => $crate::IResult::Done(i, ($($parsed),*, o))
        }
    };

    ($i:expr, ($($parsed:expr),*)) => {
        $crate::IResult::Done($i, ($($parsed),*))
    };
}

/// Run a series of parsers, returning the result of the first one which succeeds.
///
/// Optionally allows for the result to be transformed.
///
/// - **Syntax:** `alt!(THING1 | THING2 => { FUNC } | ...)`
/// - **Output:** Either `THING1` or `FUNC(THING2)` or ...
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::Ident;
/// use syn::parse::ident;
///
/// named!(ident_or_bang -> Ident,
///     alt!(ident |
///          punct!("!") => { |_| "BANG".into() }));
///
/// fn main() {
///     let input = "!";
///     ident_or_bang(input).expect("ident_or_bang");
///
///     let input = "foo";
///     ident_or_bang(input).expect("ident_or_bang");
/// }
/// ```
#[macro_export]
macro_rules! alt {
    ($i:expr, $e:ident | $($rest:tt)*) => {
        alt!($i, call!($e) | $($rest)*)
    };

    ($i:expr, $subrule:ident!( $($args:tt)*) | $($rest:tt)*) => {
        match $subrule!($i, $($args)*) {
            res @ $crate::IResult::Done(_, _) => res,
            _ => alt!($i, $($rest)*)
        }
    };

    ($i:expr, $subrule:ident!( $($args:tt)* ) => { $gen:expr } | $($rest:tt)+) => {
        match $subrule!($i, $($args)*) {
            $crate::IResult::Done(i, o) => $crate::IResult::Done(i, $gen(o)),
            $crate::IResult::Error => alt!($i, $($rest)*)
        }
    };

    ($i:expr, $e:ident => { $gen:expr } | $($rest:tt)*) => {
        alt!($i, call!($e) => { $gen } | $($rest)*)
    };

    ($i:expr, $e:ident => { $gen:expr }) => {
        alt!($i, call!($e) => { $gen })
    };

    ($i:expr, $subrule:ident!( $($args:tt)* ) => { $gen:expr }) => {
        match $subrule!($i, $($args)*) {
            $crate::IResult::Done(i, o) => $crate::IResult::Done(i, $gen(o)),
            $crate::IResult::Error => $crate::IResult::Error,
        }
    };

    ($i:expr, $e:ident) => {
        alt!($i, call!($e))
    };

    ($i:expr, $subrule:ident!( $($args:tt)*)) => {
        $subrule!($i, $($args)*)
    };
}

/// Run a series of parsers, one after another, optionally assigning the results
/// a name. Fails if any of the parsers fail.
///
/// Produces the result of evaluating the final expression in brackets with all
/// of the previously named results bound.
///
/// The variable bindings may be marked as `mut`.
///
/// - **Syntax:** `alt!(name: THING1 >> THING2 >> (RESULT))`
/// - **Output:** `RESULT`
///
/// ```rust
/// extern crate syn;
/// #[macro_use] extern crate synom;
///
/// use syn::{Ident, TokenTree};
/// use syn::parse::{ident, tt};
///
/// named!(simple_mac -> (Ident, TokenTree), do_parse!(
///     name: ident >>
///     punct!("!") >>
///     body: tt >>
///     ((name, body))));
///
/// fn main() {
///     let input = "foo!(some, random, junk)";
///     simple_mac(input).expect("macro");
/// }
/// ```
#[macro_export]
macro_rules! do_parse {
    ($i:expr, ( $($rest:expr),* )) => {
        $crate::IResult::Done($i, ( $($rest),* ))
    };

    ($i:expr, $e:ident >> $($rest:tt)*) => {
        do_parse!($i, call!($e) >> $($rest)*)
    };

    ($i:expr, $submac:ident!( $($args:tt)* ) >> $($rest:tt)*) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, _) =>
                do_parse!(i, $($rest)*),
        }
    };

    ($i:expr, $field:ident : $e:ident >> $($rest:tt)*) => {
        do_parse!($i, $field: call!($e) >> $($rest)*)
    };

    ($i:expr, $field:ident : $submac:ident!( $($args:tt)* ) >> $($rest:tt)*) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) => {
                let $field = o;
                do_parse!(i, $($rest)*)
            },
        }
    };

    ($i:expr, mut $field:ident : $e:ident >> $($rest:tt)*) => {
        do_parse!($i, mut $field: call!($e) >> $($rest)*)
    };

    ($i:expr, mut $field:ident : $submac:ident!( $($args:tt)* ) >> $($rest:tt)*) => {
        match $submac!($i, $($args)*) {
            $crate::IResult::Error => $crate::IResult::Error,
            $crate::IResult::Done(i, o) => {
                let mut $field = o;
                do_parse!(i, $($rest)*)
            },
        }
    };
}