winnow 1.0.2

//! Basic types to build the parsers

use crate::combinator::impls;
#[cfg(feature = "unstable-recover")]
#[cfg(feature = "std")]
use crate::error::FromRecoverableError;
use crate::error::{AddContext, FromExternalError, ParseError, ParserError, Result};
use crate::stream::{Compare, Location, ParseSlice, Stream, StreamIsPartial};
#[cfg(feature = "unstable-recover")]
#[cfg(feature = "std")]
use crate::stream::{Recover, Recoverable};

/// Core trait for parsing
///
/// The simplest way to implement a `Parser` is with a function
/// ```rust
/// use winnow::prelude::*;
///
/// fn empty(input: &mut &str) -> ModalResult<()> {
///     let output = ();
///     Ok(output)
/// }
///
/// let (input, output) = empty.parse_peek("Hello").unwrap();
/// assert_eq!(input, "Hello");  // We didn't consume any input
/// ```
///
/// which can be made stateful by returning a function
/// ```rust
/// use winnow::prelude::*;
///
/// fn empty<O: Clone>(output: O) -> impl FnMut(&mut &str) -> ModalResult<O> {
///     move |input: &mut &str| {
///         let output = output.clone();
///         Ok(output)
///     }
/// }
///
/// let (input, output) = empty("World").parse_peek("Hello").unwrap();
/// assert_eq!(input, "Hello");  // We didn't consume any input
/// assert_eq!(output, "World");
/// ```
///
/// Additionally, some basic types implement `Parser` as well, including
/// - `u8` and `char`, see [`winnow::token::one_of`][crate::token::one_of]
/// - `&[u8]` and `&str`, see [`winnow::token::literal`][crate::token::literal]
pub trait Parser<I, O, E> {
    /// Parse all of `input`, generating `O` from it
    ///
    /// This is intended for integrating your parser into the rest of your application.
    ///
    /// For one [`Parser`] to drive another [`Parser`] forward or for
    /// [incremental parsing][StreamIsPartial], see instead [`Parser::parse_next`].
    ///
    /// This assumes the [`Parser`] intends to read all of `input` and will return an
    /// [`eof`][crate::combinator::eof] error if it does not.
    /// To ignore trailing `input`, combine your parser with a [`rest`][crate::token::rest]
    /// (e.g. `(parser, rest).parse(input)`).
    ///
    /// See also the [tutorial][crate::_tutorial::chapter_6].
    #[inline]
    fn parse(&mut self, mut input: I) -> Result<O, ParseError<I, <E as ParserError<I>>::Inner>>
    where
        Self: core::marker::Sized,
        I: Stream,
        // Force users to deal with `Incomplete` when `StreamIsPartial<true>`
        I: StreamIsPartial,
        E: ParserError<I>,
        <E as ParserError<I>>::Inner: ParserError<I>,
    {
        debug_assert!(
            !I::is_partial_supported(),
            "partial streams need to handle `ErrMode::Incomplete`"
        );

        let start = input.checkpoint();
        let (o, _) = (self.by_ref(), crate::combinator::eof)
            .parse_next(&mut input)
            .map_err(|e| {
                let e = e.into_inner().unwrap_or_else(|_err| {
                    panic!("complete parsers should not report `ErrMode::Incomplete(_)`")
                });
                ParseError::new(input, start, e)
            })?;
        Ok(o)
    }

    /// Repeat this parse until all of `input` is consumed, generating `O` from it
    ///
    /// This is intended for integrating your parser into the rest of your application.
    /// To instead iterate inside of a parser, see [iterator][crate::combinator::iterator].
    ///
    /// This assumes the [`Parser`] intends to read all of `input` and will return an
    /// [`eof`][crate::combinator::eof] error if it does not.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::ascii::dec_uint;
    /// # use winnow::ascii::newline;
    /// # use winnow::combinator::terminated;
    /// # use winnow::combinator::opt;
    /// # use winnow::prelude::*;
    /// fn number(input: &mut &str) -> Result<u32, ()> {
    ///   terminated(dec_uint, opt(newline)).parse_next(input)
    /// }
    ///
    /// let input = "10\n20\n30";
    /// let numbers = number.parse_iter(input)
    ///     .map(|r| r.unwrap()).collect::<Vec<_>>();
    /// assert_eq!(numbers, vec![10, 20, 30]);
    /// # }
    /// ```
    #[inline]
    fn parse_iter(&mut self, input: I) -> impls::ParseIter<'_, Self, I, O, E>
    where
        Self: core::marker::Sized,
        I: Stream,
        // Force users to deal with `Incomplete` when `StreamIsPartial<true>`
        I: StreamIsPartial,
        E: ParserError<I>,
        <E as ParserError<I>>::Inner: ParserError<I>,
    {
        debug_assert!(
            !I::is_partial_supported(),
            "partial streams need to handle `ErrMode::Incomplete`"
        );

        let start = input.checkpoint();
        impls::ParseIter {
            parser: self,
            input: Some(input),
            start: Some(start),
            marker: Default::default(),
        }
    }

    /// Take tokens from the [`Stream`], turning it into the output
    ///
    /// This includes advancing the input [`Stream`] to the next location.
    ///
    /// On error, `input` will be left pointing at the error location.
    ///
    /// This is intended for a [`Parser`] to drive another [`Parser`] forward or for
    /// [incremental parsing][StreamIsPartial]
    fn parse_next(&mut self, input: &mut I) -> Result<O, E>;

    /// Take tokens from the [`Stream`], turning it into the output
    ///
    /// This returns a copy of the [`Stream`] advanced to the next location.
    ///
    /// <div class="warning">
    ///
    /// Generally, prefer [`Parser::parse_next`].
    /// This is primarily intended for:
    /// - Migrating from older versions / `nom`
    /// - Testing [`Parser`]s
    ///
    /// For look-ahead parsing, see instead [`peek`][crate::combinator::peek].
    ///
    /// </div>
    #[inline(always)]
    fn parse_peek(&mut self, mut input: I) -> Result<(I, O), E> {
        match self.parse_next(&mut input) {
            Ok(o) => Ok((input, o)),
            Err(err) => Err(err),
        }
    }

    /// Treat `&mut Self` as a parser
    ///
    /// This helps when needing to move a `Parser` when all you have is a `&mut Parser`.
    ///
    /// # Example
    ///
    /// Because parsers are `FnMut`, they can be called multiple times. This prevents moving `f`
    /// into [`length_take`][crate::binary::length_take] and `g` into
    /// [`Parser::complete_err`]:
    /// ```rust,compile_fail
    /// # use winnow::prelude::*;
    /// # use winnow::Parser;
    /// # use winnow::error::ParserError;
    /// # use winnow::binary::length_take;
    /// pub fn length_value<'i, O, E: ParserError<&'i [u8]>>(
    ///     mut f: impl Parser<&'i [u8], usize, E>,
    ///     mut g: impl Parser<&'i [u8], O, E>
    /// ) -> impl Parser<&'i [u8], O, E> {
    ///   move |i: &mut &'i [u8]| {
    ///     let mut data = length_take(f).parse_next(i)?;
    ///     let o = g.complete_err().parse_next(&mut data)?;
    ///     Ok(o)
    ///   }
    /// }
    /// ```
    ///
    /// By adding `by_ref`, we can make this work:
    /// ```rust
    /// # #[cfg(feature = "binary")] {
    /// # use winnow::prelude::*;
    /// # use winnow::Parser;
    /// # use winnow::error::ParserError;
    /// # use winnow::binary::length_take;
    /// pub fn length_value<'i, O, E: ParserError<&'i [u8]>>(
    ///     mut f: impl Parser<&'i [u8], usize, E>,
    ///     mut g: impl Parser<&'i [u8], O, E>
    /// ) -> impl Parser<&'i [u8], O, E> {
    ///   move |i: &mut &'i [u8]| {
    ///     let mut data = length_take(f.by_ref()).parse_next(i)?;
    ///     let o = g.by_ref().complete_err().parse_next(&mut data)?;
    ///     Ok(o)
    ///   }
    /// }
    /// # }
    /// ```
    #[inline(always)]
    fn by_ref(&mut self) -> impls::ByRef<'_, Self, I, O, E>
    where
        Self: core::marker::Sized,
    {
        impls::ByRef {
            p: self,
            marker: Default::default(),
        }
    }

    /// Produce the provided value
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::prelude::*;
    /// use winnow::ascii::alpha1;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<i32> {
    ///     alpha1.value(1234).parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("abcd"), Ok(("", 1234)));
    /// assert!(parser.parse_peek("123abcd;").is_err());
    /// # }
    /// ```
    #[doc(alias = "to")]
    #[inline(always)]
    fn value<O2>(self, val: O2) -> impls::Value<Self, I, O, O2, E>
    where
        Self: core::marker::Sized,
        O2: Clone,
    {
        impls::Value {
            parser: self,
            val,
            marker: Default::default(),
        }
    }

    /// Produce a type's default value
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::prelude::*;
    /// use winnow::ascii::alpha1;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<u32> {
    ///     alpha1.default_value().parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("abcd"), Ok(("", 0)));
    /// assert!(parser.parse_peek("123abcd;").is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn default_value<O2>(self) -> impls::DefaultValue<Self, I, O, O2, E>
    where
        Self: core::marker::Sized,
        O2: core::default::Default,
    {
        impls::DefaultValue {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Discards the output of the `Parser`
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::prelude::*;
    /// use winnow::ascii::alpha1;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<()> {
    ///     alpha1.void().parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("abcd"), Ok(("", ())));
    /// assert!(parser.parse_peek("123abcd;").is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn void(self) -> impls::Void<Self, I, O, E>
    where
        Self: core::marker::Sized,
    {
        impls::Void {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Convert the parser's output to another type using [`std::convert::From`]
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::error::ContextError;
    /// use winnow::ascii::alpha1;
    ///
    /// fn parser1<'s>(i: &mut &'s str) -> ModalResult<&'s str> {
    ///   alpha1(i)
    /// }
    ///
    /// let mut parser2 = parser1.output_into();
    ///
    /// // the parser converts the &str output of the child parser into a Vec<u8>
    /// let bytes: ModalResult<(_, Vec<u8>), _> = parser2.parse_peek("abcd");
    /// assert_eq!(bytes, Ok(("", vec![97, 98, 99, 100])));
    /// # }
    /// ```
    #[inline(always)]
    fn output_into<O2>(self) -> impls::OutputInto<Self, I, O, O2, E>
    where
        Self: core::marker::Sized,
        O: Into<O2>,
    {
        impls::OutputInto {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Produce the consumed input as produced value.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::prelude::*;
    /// use winnow::ascii::{alpha1};
    /// use winnow::combinator::separated_pair;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<&'i str> {
    ///     separated_pair(alpha1, ',', alpha1).take().parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("abcd,efgh"), Ok(("", "abcd,efgh")));
    /// assert!(parser.parse_peek("abcd;").is_err());
    /// # }
    /// ```
    #[doc(alias = "concat")]
    #[doc(alias = "recognize")]
    #[inline(always)]
    fn take(self) -> impls::Take<Self, I, O, E>
    where
        Self: core::marker::Sized,
        I: Stream,
    {
        impls::Take {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Produce the consumed input with the output
    ///
    /// Functions similarly to [take][Parser::take] except it
    /// returns the parser output as well.
    ///
    /// This can be useful especially in cases where the output is not the same type
    /// as the input, or the input is a user defined type.
    ///
    /// Returned tuple is of the format `(produced output, consumed input)`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::{error::ErrMode};
    /// use winnow::ascii::{alpha1};
    /// use winnow::token::literal;
    /// use winnow::combinator::separated_pair;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<(bool, &'i str)> {
    ///     separated_pair(alpha1, ',', alpha1).value(true).with_taken().parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("abcd,efgh1"), Ok(("1", (true, "abcd,efgh"))));
    /// assert!(parser.parse_peek("abcd;").is_err());
    /// # }
    /// ```
    #[doc(alias = "consumed")]
    #[doc(alias = "with_recognized")]
    #[inline(always)]
    fn with_taken(self) -> impls::WithTaken<Self, I, O, E>
    where
        Self: core::marker::Sized,
        I: Stream,
    {
        impls::WithTaken {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Produce the location of the consumed input as produced value.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::{error::ErrMode, stream::Stream};
    /// # use std::ops::Range;
    /// use winnow::stream::LocatingSlice;
    /// use winnow::ascii::alpha1;
    /// use winnow::combinator::separated_pair;
    ///
    /// fn parser<'i>(input: &mut LocatingSlice<&'i str>) -> ModalResult<(Range<usize>, Range<usize>)> {
    ///     separated_pair(alpha1.span(), ',', alpha1.span()).parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse(LocatingSlice::new("abcd,efgh")), Ok((0..4, 5..9)));
    /// assert!(parser.parse_peek(LocatingSlice::new("abcd;")).is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn span(self) -> impls::Span<Self, I, O, E>
    where
        Self: core::marker::Sized,
        I: Stream + Location,
    {
        impls::Span {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Produce the location of consumed input with the output
    ///
    /// Functions similarly to [`Parser::span`] except it
    /// returns the parser output as well.
    ///
    /// This can be useful especially in cases where the output is not the same type
    /// as the input, or the input is a user defined type.
    ///
    /// Returned tuple is of the format `(produced output, consumed input)`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::{error::ErrMode, stream::Stream};
    /// # use std::ops::Range;
    /// use winnow::stream::LocatingSlice;
    /// use winnow::ascii::alpha1;
    /// use winnow::token::literal;
    /// use winnow::combinator::separated_pair;
    ///
    /// fn parser<'i>(input: &mut LocatingSlice<&'i str>) -> ModalResult<((usize, Range<usize>), (usize, Range<usize>))> {
    ///     separated_pair(alpha1.value(1).with_span(), ',', alpha1.value(2).with_span()).parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse(LocatingSlice::new("abcd,efgh")), Ok(((1, 0..4), (2, 5..9))));
    /// assert!(parser.parse_peek(LocatingSlice::new("abcd;")).is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn with_span(self) -> impls::WithSpan<Self, I, O, E>
    where
        Self: core::marker::Sized,
        I: Stream + Location,
    {
        impls::WithSpan {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Maps a function over the output of a parser
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::ascii::digit1;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<usize> {
    ///     digit1.map(|s: &str| s.len()).parse_next(input)
    /// }
    ///
    /// // the parser will count how many characters were returned by digit1
    /// assert_eq!(parser.parse_peek("123456"), Ok(("", 6)));
    ///
    /// // this will fail if digit1 fails
    /// assert!(parser.parse_peek("abc").is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn map<G, O2>(self, map: G) -> impls::Map<Self, G, I, O, O2, E>
    where
        G: FnMut(O) -> O2,
        Self: core::marker::Sized,
    {
        impls::Map {
            parser: self,
            map,
            marker: Default::default(),
        }
    }

    /// Applies a function returning a `Result` over the output of a parser.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::prelude::*;
    /// use winnow::ascii::digit1;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<u8> {
    ///     digit1.try_map(|s: &str| s.parse::<u8>()).parse_next(input)
    /// }
    ///
    /// // the parser will convert the result of digit1 to a number
    /// assert_eq!(parser.parse_peek("123"), Ok(("", 123)));
    ///
    /// // this will fail if digit1 fails
    /// assert!(parser.parse_peek("abc").is_err());
    ///
    /// // this will fail if the mapped function fails (a `u8` is too small to hold `123456`)
    /// assert!(parser.parse_peek("123456").is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn try_map<G, O2, E2>(self, map: G) -> impls::TryMap<Self, G, I, O, O2, E, E2>
    where
        Self: core::marker::Sized,
        G: FnMut(O) -> Result<O2, E2>,
        I: Stream,
        E: FromExternalError<I, E2>,
        E: ParserError<I>,
    {
        impls::TryMap {
            parser: self,
            map,
            marker: Default::default(),
        }
    }

    /// Apply both [`Parser::verify`] and [`Parser::map`].
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::prelude::*;
    /// use winnow::ascii::digit1;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<u8> {
    ///     digit1.verify_map(|s: &str| s.parse::<u8>().ok()).parse_next(input)
    /// }
    ///
    /// // the parser will convert the result of digit1 to a number
    /// assert_eq!(parser.parse_peek("123"), Ok(("", 123)));
    ///
    /// // this will fail if digit1 fails
    /// assert!(parser.parse_peek("abc").is_err());
    ///
    /// // this will fail if the mapped function fails (a `u8` is too small to hold `123456`)
    /// assert!(parser.parse_peek("123456").is_err());
    /// # }
    /// ```
    #[doc(alias = "satisfy_map")]
    #[doc(alias = "filter_map")]
    #[doc(alias = "map_opt")]
    #[inline(always)]
    fn verify_map<G, O2>(self, map: G) -> impls::VerifyMap<Self, G, I, O, O2, E>
    where
        Self: core::marker::Sized,
        G: FnMut(O) -> Option<O2>,
        I: Stream,
        E: ParserError<I>,
    {
        impls::VerifyMap {
            parser: self,
            map,
            marker: Default::default(),
        }
    }

    /// Creates a parser from the output of this one
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "binary")] {
    /// # use winnow::{error::ErrMode, ModalResult, Parser};
    /// use winnow::token::take;
    /// use winnow::binary::u8;
    ///
    /// fn length_take<'s>(input: &mut &'s [u8]) -> ModalResult<&'s [u8]> {
    ///     u8.flat_map(take).parse_next(input)
    /// }
    ///
    /// assert_eq!(length_take.parse_peek(&[2, 0, 1, 2][..]), Ok((&[2][..], &[0, 1][..])));
    /// assert!(length_take.parse_peek(&[4, 0, 1, 2][..]).is_err());
    /// # }
    /// ```
    ///
    /// which is the same as
    /// ```rust
    /// # #[cfg(feature = "binary")] {
    /// # use winnow::{error::ErrMode, ModalResult, Parser};
    /// use winnow::token::take;
    /// use winnow::binary::u8;
    ///
    /// fn length_take<'s>(input: &mut &'s [u8]) -> ModalResult<&'s [u8]> {
    ///     let length = u8.parse_next(input)?;
    ///     let data = take(length).parse_next(input)?;
    ///     Ok(data)
    /// }
    ///
    /// assert_eq!(length_take.parse_peek(&[2, 0, 1, 2][..]), Ok((&[2][..], &[0, 1][..])));
    /// assert!(length_take.parse_peek(&[4, 0, 1, 2][..]).is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn flat_map<G, H, O2>(self, map: G) -> impls::FlatMap<Self, G, H, I, O, O2, E>
    where
        Self: core::marker::Sized,
        G: FnMut(O) -> H,
        H: Parser<I, O2, E>,
    {
        impls::FlatMap {
            f: self,
            g: map,
            marker: Default::default(),
        }
    }

    /// Applies a second parser over the output of the first one
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::prelude::*;
    /// use winnow::ascii::digit1;
    /// use winnow::token::take;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<&'i str> {
    ///     take(5u8).and_then(digit1).parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("12345"), Ok(("", "12345")));
    /// assert_eq!(parser.parse_peek("123ab"), Ok(("", "123")));
    /// assert!(parser.parse_peek("123").is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn and_then<G, O2>(self, inner: G) -> impls::AndThen<Self, G, I, O, O2, E>
    where
        Self: core::marker::Sized,
        G: Parser<O, O2, E>,
        O: StreamIsPartial,
        I: Stream,
    {
        impls::AndThen {
            outer: self,
            inner,
            marker: Default::default(),
        }
    }

    /// Apply [`std::str::FromStr`] to the output of the parser
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// use winnow::{error::ErrMode, Parser};
    /// use winnow::ascii::digit1;
    ///
    /// fn parser<'s>(input: &mut &'s str) -> ModalResult<u64> {
    ///     digit1.parse_to().parse_next(input)
    /// }
    ///
    /// // the parser will count how many characters were returned by digit1
    /// assert_eq!(parser.parse_peek("123456"), Ok(("", 123456)));
    ///
    /// // this will fail if digit1 fails
    /// assert!(parser.parse_peek("abc").is_err());
    /// # }
    /// ```
    #[doc(alias = "from_str")]
    #[inline(always)]
    fn parse_to<O2>(self) -> impls::ParseTo<Self, I, O, O2, E>
    where
        Self: core::marker::Sized,
        I: Stream,
        O: ParseSlice<O2>,
        E: ParserError<I>,
    {
        impls::ParseTo {
            p: self,
            marker: Default::default(),
        }
    }

    /// Returns the output of the child parser if it satisfies a verification function.
    ///
    /// The verification function takes as argument a reference to the output of the
    /// parser.
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::ascii::alpha1;
    /// # use winnow::prelude::*;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<&'i str> {
    ///     alpha1.verify(|s: &str| s.len() == 4).parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("abcd"), Ok(("", "abcd")));
    /// assert!(parser.parse_peek("abcde").is_err());
    /// assert!(parser.parse_peek("123abcd;").is_err());
    /// # }
    /// ```
    #[doc(alias = "satisfy")]
    #[doc(alias = "filter")]
    #[inline(always)]
    fn verify<G, O2>(self, filter: G) -> impls::Verify<Self, G, I, O, O2, E>
    where
        Self: core::marker::Sized,
        G: FnMut(&O2) -> bool,
        I: Stream,
        O: core::borrow::Borrow<O2>,
        O2: ?Sized,
        E: ParserError<I>,
    {
        impls::Verify {
            parser: self,
            filter,
            marker: Default::default(),
        }
    }

    /// If parsing fails, add context to the error
    ///
    /// This is used mainly to add user friendly information
    /// to errors when backtracking through a parse tree.
    ///
    /// See also [tutorial][crate::_tutorial::chapter_7].
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::ascii::digit1;
    /// # use winnow::error::StrContext;
    /// # use winnow::error::StrContextValue;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<&'i str> {
    ///     digit1
    ///       .context(StrContext::Expected(StrContextValue::Description("digit")))
    ///       .parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("123456"), Ok(("", "123456")));
    /// assert!(parser.parse_peek("abc").is_err());
    /// # }
    /// ```
    #[doc(alias = "labelled")]
    #[inline(always)]
    fn context<C>(self, context: C) -> impls::Context<Self, I, O, E, C>
    where
        Self: core::marker::Sized,
        I: Stream,
        E: AddContext<I, C>,
        E: ParserError<I>,
        C: Clone + core::fmt::Debug,
    {
        impls::Context {
            parser: self,
            context,
            marker: Default::default(),
        }
    }

    /// If parsing fails, dynamically add context to the error
    ///
    /// This is used mainly to add user friendly information
    /// to errors when backtracking through a parse tree.
    ///
    /// See also [tutorial][crate::_tutorial::chapter_7].
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::{error::ErrMode, Parser};
    /// # use winnow::ascii::digit1;
    /// # use winnow::error::StrContext;
    /// # use winnow::error::StrContextValue;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> ModalResult<&'i str> {
    ///     digit1
    ///       .context_with(|| {
    ///         "0123456789".chars().map(|c| StrContext::Expected(c.into()))
    ///       })
    ///       .parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("123456"), Ok(("", "123456")));
    /// assert!(parser.parse_peek("abc").is_err());
    /// # }
    /// ```
    #[doc(alias = "labelled")]
    #[inline(always)]
    fn context_with<F, C, FI>(self, context: F) -> impls::ContextWith<Self, I, O, E, F, C, FI>
    where
        Self: core::marker::Sized,
        I: Stream,
        E: AddContext<I, C>,
        E: ParserError<I>,
        F: Fn() -> FI + Clone,
        C: core::fmt::Debug,
        FI: Iterator<Item = C>,
    {
        impls::ContextWith {
            parser: self,
            context,
            marker: Default::default(),
        }
    }

    /// Maps a function over the error of a parser
    ///
    /// # Example
    ///
    /// ```rust
    /// # #[cfg(feature = "ascii")] {
    /// # use winnow::prelude::*;
    /// # use winnow::Parser;
    /// # use winnow::Result;
    /// # use winnow::ascii::digit1;
    /// # use winnow::error::StrContext;
    /// # use winnow::error::AddContext;
    /// # use winnow::error::ContextError;
    ///
    /// fn parser<'i>(input: &mut &'i str) -> Result<&'i str> {
    ///     digit1.map_err(|mut e: ContextError| {
    ///         e.extend("0123456789".chars().map(|c| StrContext::Expected(c.into())));
    ///         e
    ///     }).parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek("123456"), Ok(("", "123456")));
    /// assert!(parser.parse_peek("abc").is_err());
    /// # }
    /// ```
    #[inline(always)]
    fn map_err<G, E2>(self, map: G) -> impls::MapErr<Self, G, I, O, E, E2>
    where
        G: FnMut(E) -> E2,
        Self: core::marker::Sized,
    {
        impls::MapErr {
            parser: self,
            map,
            marker: Default::default(),
        }
    }

    /// Transforms [`Incomplete`][crate::error::ErrMode::Incomplete] into [`Backtrack`][crate::error::ErrMode::Backtrack]
    ///
    /// # Example
    ///
    /// ```rust
    /// # use winnow::{error::ErrMode, error::InputError, stream::Partial, Parser};
    /// # use winnow::token::take;
    /// # use winnow::prelude::*;
    /// # fn main() {
    ///
    /// fn parser<'i>(input: &mut Partial<&'i str>) -> ModalResult<&'i str, InputError<Partial<&'i str>>> {
    ///     take(5u8).complete_err().parse_next(input)
    /// }
    ///
    /// assert_eq!(parser.parse_peek(Partial::new("abcdefg")), Ok((Partial::new("fg"), "abcde")));
    /// assert_eq!(parser.parse_peek(Partial::new("abcd")), Err(ErrMode::Backtrack(InputError::at(Partial::new("abcd")))));
    /// # }
    /// ```
    #[inline(always)]
    fn complete_err(self) -> impls::CompleteErr<Self, I, O, E>
    where
        Self: core::marker::Sized,
    {
        impls::CompleteErr {
            p: self,
            marker: Default::default(),
        }
    }

    /// Convert the parser's error to another type using [`std::convert::From`]
    #[inline(always)]
    fn err_into<E2>(self) -> impls::ErrInto<Self, I, O, E, E2>
    where
        Self: core::marker::Sized,
        E: Into<E2>,
    {
        impls::ErrInto {
            parser: self,
            marker: Default::default(),
        }
    }

    /// Recover from an error by skipping everything `recover` consumes and trying again
    ///
    /// If `recover` consumes nothing, the error is returned, allowing an alternative recovery
    /// method.
    ///
    /// This commits the parse result, preventing alternative branch paths like with
    /// [`winnow::combinator::alt`][crate::combinator::alt].
    #[inline(always)]
    #[cfg(feature = "unstable-recover")]
    #[cfg(feature = "std")]
    fn retry_after<R>(self, recover: R) -> impls::RetryAfter<Self, R, I, O, E>
    where
        Self: core::marker::Sized,
        R: Parser<I, (), E>,
        I: Stream,
        I: Recover<E>,
        E: ParserError<I> + FromRecoverableError<I, E>,
    {
        impls::RetryAfter {
            parser: self,
            recover,
            marker: Default::default(),
        }
    }

    /// Recover from an error by skipping this parse and everything `recover` consumes
    ///
    /// This commits the parse result, preventing alternative branch paths like with
    /// [`winnow::combinator::alt`][crate::combinator::alt].
    #[inline(always)]
    #[cfg(feature = "unstable-recover")]
    #[cfg(feature = "std")]
    fn resume_after<R>(self, recover: R) -> impls::ResumeAfter<Self, R, I, O, E>
    where
        Self: core::marker::Sized,
        R: Parser<I, (), E>,
        I: Stream,
        I: Recover<E>,
        E: ParserError<I> + FromRecoverableError<I, E>,
    {
        impls::ResumeAfter {
            parser: self,
            recover,
            marker: Default::default(),
        }
    }
}

impl<I, O, E, F> Parser<I, O, E> for F
where
    F: FnMut(&mut I) -> Result<O, E>,
    I: Stream,
{
    #[inline(always)]
    fn parse_next(&mut self, i: &mut I) -> Result<O, E> {
        self(i)
    }
}

/// This is a shortcut for [`one_of`][crate::token::one_of].
///
/// # Example
///
/// ```rust
/// # use winnow::prelude::*;
/// # use winnow::{error::ErrMode, error::ContextError};
/// fn parser<'s>(i: &mut &'s [u8]) -> ModalResult<u8>  {
///     b'a'.parse_next(i)
/// }
/// assert_eq!(parser.parse_peek(&b"abc"[..]), Ok((&b"bc"[..], b'a')));
/// assert!(parser.parse_peek(&b" abc"[..]).is_err());
/// assert!(parser.parse_peek(&b"bc"[..]).is_err());
/// assert!(parser.parse_peek(&b""[..]).is_err());
/// ```
impl<I, E> Parser<I, u8, E> for u8
where
    I: StreamIsPartial,
    I: Stream,
    I: Compare<u8>,
    E: ParserError<I>,
{
    #[inline(always)]
    fn parse_next(&mut self, i: &mut I) -> Result<u8, E> {
        crate::token::literal(*self).value(*self).parse_next(i)
    }
}

/// This is a shortcut for [`one_of`][crate::token::one_of].
///
/// # Example
///
/// ```rust
/// # use winnow::prelude::*;
/// # use winnow::{error::ErrMode, error::ContextError};
/// fn parser<'s>(i: &mut &'s str) -> ModalResult<char> {
///     'a'.parse_next(i)
/// }
/// assert_eq!(parser.parse_peek("abc"), Ok(("bc", 'a')));
/// assert!(parser.parse_peek(" abc").is_err());
/// assert!(parser.parse_peek("bc").is_err());
/// assert!(parser.parse_peek("").is_err());
/// ```
impl<I, E> Parser<I, char, E> for char
where
    I: StreamIsPartial,
    I: Stream,
    I: Compare<char>,
    E: ParserError<I>,
{
    #[inline(always)]
    fn parse_next(&mut self, i: &mut I) -> Result<char, E> {
        crate::token::literal(*self).value(*self).parse_next(i)
    }
}

/// This is a shortcut for [`literal`][crate::token::literal].
///
/// # Example
/// ```rust
/// # use winnow::prelude::*;
/// # use winnow::{error::ErrMode, error::ContextError, error::Needed};
/// # use winnow::combinator::alt;
/// # use winnow::token::take;
///
/// fn parser<'s>(s: &mut &'s [u8]) -> ModalResult<&'s [u8]> {
///   alt((&"Hello"[..], take(5usize))).parse_next(s)
/// }
///
/// assert_eq!(parser.parse_peek(&b"Hello, World!"[..]), Ok((&b", World!"[..], &b"Hello"[..])));
/// assert_eq!(parser.parse_peek(&b"Something"[..]), Ok((&b"hing"[..], &b"Somet"[..])));
/// assert!(parser.parse_peek(&b"Some"[..]).is_err());
/// assert!(parser.parse_peek(&b""[..]).is_err());
/// ```
impl<'s, I, E: ParserError<I>> Parser<I, <I as Stream>::Slice, E> for &'s [u8]
where
    I: Compare<&'s [u8]> + StreamIsPartial,
    I: Stream,
{
    #[inline(always)]
    fn parse_next(&mut self, i: &mut I) -> Result<<I as Stream>::Slice, E> {
        crate::token::literal(*self).parse_next(i)
    }
}

/// This is a shortcut for [`literal`][crate::token::literal].
///
/// # Example
/// ```rust
/// # use winnow::prelude::*;
/// # use winnow::{error::ErrMode, error::ContextError, error::Needed};
/// # use winnow::combinator::alt;
/// # use winnow::token::take;
///
/// fn parser<'s>(s: &mut &'s [u8]) -> ModalResult<&'s [u8]> {
///   alt((b"Hello", take(5usize))).parse_next(s)
/// }
///
/// assert_eq!(parser.parse_peek(&b"Hello, World!"[..]), Ok((&b", World!"[..], &b"Hello"[..])));
/// assert_eq!(parser.parse_peek(&b"Something"[..]), Ok((&b"hing"[..], &b"Somet"[..])));
/// assert!(parser.parse_peek(&b"Some"[..]).is_err());
/// assert!(parser.parse_peek(&b""[..]).is_err());
/// ```
impl<'s, I, E: ParserError<I>, const N: usize> Parser<I, <I as Stream>::Slice, E> for &'s [u8; N]
where
    I: Compare<&'s [u8; N]> + StreamIsPartial,
    I: Stream,
{
    #[inline(always)]
    fn parse_next(&mut self, i: &mut I) -> Result<<I as Stream>::Slice, E> {
        crate::token::literal(*self).parse_next(i)
    }
}

/// This is a shortcut for [`literal`][crate::token::literal].
///
/// # Example
/// ```rust
/// # use winnow::prelude::*;
/// # use winnow::{error::ErrMode, error::ContextError};
/// # use winnow::combinator::alt;
/// # use winnow::token::take;
///
/// fn parser<'s>(s: &mut &'s str) -> ModalResult<&'s str> {
///   alt(("Hello", take(5usize))).parse_next(s)
/// }
///
/// assert_eq!(parser.parse_peek("Hello, World!"), Ok((", World!", "Hello")));
/// assert_eq!(parser.parse_peek("Something"), Ok(("hing", "Somet")));
/// assert!(parser.parse_peek("Some").is_err());
/// assert!(parser.parse_peek("").is_err());
/// ```
impl<'s, I, E: ParserError<I>> Parser<I, <I as Stream>::Slice, E> for &'s str
where
    I: Compare<&'s str> + StreamIsPartial,
    I: Stream,
{
    #[inline(always)]
    fn parse_next(&mut self, i: &mut I) -> Result<<I as Stream>::Slice, E> {
        crate::token::literal(*self).parse_next(i)
    }
}

impl<I: Stream, E: ParserError<I>> Parser<I, (), E> for () {
    #[inline(always)]
    fn parse_next(&mut self, _i: &mut I) -> Result<(), E> {
        Ok(())
    }
}

macro_rules! impl_parser_for_tuple {
    ($($index:tt $parser:ident $output:ident),+) => (
        #[allow(non_snake_case)]
        impl<I: Stream, $($output),+, E: ParserError<I>, $($parser),+> Parser<I, ($($output),+,), E> for ($($parser),+,)
        where
            $($parser: Parser<I, $output, E>),+
        {
            #[inline(always)]
            fn parse_next(&mut self, i: &mut I) -> Result<($($output),+,), E> {
                $(let $output = self.$index.parse_next(i)?;)+

                Ok(($($output),+,))
            }
        }
    )
}

macro_rules! impl_parser_for_tuples {
    ($index1:tt $parser1:ident $output1:ident, $($index:tt $parser:ident $output:ident),+) => {
        impl_parser_for_tuples!(__impl $index1 $parser1 $output1; $($index $parser $output),+);
    };
    (__impl $($index:tt $parser:ident $output:ident),+; $index1:tt $parser1:ident $output1:ident $(,$index2:tt $parser2:ident $output2:ident)*) => {
        impl_parser_for_tuple!($($index $parser $output),+);
        impl_parser_for_tuples!(__impl $($index $parser $output),+, $index1 $parser1 $output1; $($index2 $parser2 $output2),*);
    };
    (__impl $($index:tt $parser:ident $output:ident),+;) => {
        impl_parser_for_tuple!($($index $parser $output),+);
    }
}

impl_parser_for_tuples!(
  0 P0 O0,
  1 P1 O1,
  2 P2 O2,
  3 P3 O3,
  4 P4 O4,
  5 P5 O5,
  6 P6 O6,
  7 P7 O7,
  8 P8 O8,
  9 P9 O9,
  10 P10 O10
);

#[cfg(feature = "alloc")]
use alloc::boxed::Box;

#[cfg(feature = "alloc")]
impl<I, O, E> Parser<I, O, E> for Box<dyn Parser<I, O, E> + '_> {
    #[inline(always)]
    fn parse_next(&mut self, i: &mut I) -> Result<O, E> {
        (**self).parse_next(i)
    }
}

/// Trait alias for [`Parser`] to be used with [`ModalResult`][crate::error::ModalResult]
pub trait ModalParser<I, O, E>: Parser<I, O, crate::error::ErrMode<E>> {}

impl<I, O, E, P> ModalParser<I, O, E> for P where P: Parser<I, O, crate::error::ErrMode<E>> {}

/// Collect all errors when parsing the input
///
/// [`Parser`]s will need to use [`Recoverable<I, _>`] for their input.
#[cfg(feature = "unstable-recover")]
#[cfg(feature = "std")]
pub trait RecoverableParser<I, O, R, E> {
    /// Collect all errors when parsing the input
    ///
    /// If `self` fails, this acts like [`Parser::resume_after`] and returns `Ok(None)`.
    /// Generally, this should be avoided by using
    /// [`Parser::retry_after`] and [`Parser::resume_after`] throughout your parser.
    ///
    /// The empty `input` is returned to allow turning the errors into [`ParserError`]s.
    fn recoverable_parse(&mut self, input: I) -> (I, Option<O>, Vec<R>);
}

#[cfg(feature = "unstable-recover")]
#[cfg(feature = "std")]
impl<P, I, O, R, E> RecoverableParser<I, O, R, E> for P
where
    P: Parser<Recoverable<I, R>, O, E>,
    I: Stream,
    I: StreamIsPartial,
    R: FromRecoverableError<Recoverable<I, R>, E>,
    R: core::fmt::Debug,
    E: FromRecoverableError<Recoverable<I, R>, E>,
    E: ParserError<Recoverable<I, R>>,
    E: core::fmt::Debug,
{
    fn recoverable_parse(&mut self, input: I) -> (I, Option<O>, Vec<R>) {
        debug_assert!(
            !I::is_partial_supported(),
            "partial streams need to handle `ErrMode::Incomplete`"
        );

        let start = input.checkpoint();
        let mut input = Recoverable::new(input);
        let start_token = input.checkpoint();
        let result = (
            self.by_ref(),
            crate::combinator::eof.resume_after(crate::token::rest.void()),
        )
            .parse_next(&mut input);

        let (o, err) = match result {
            Ok((o, _)) => (Some(o), None),
            Err(err) => {
                let err_start = input.checkpoint();
                let err = R::from_recoverable_error(&start_token, &err_start, &input, err);
                (None, Some(err))
            }
        };

        let (mut input, mut errs) = input.into_parts();
        input.reset(&start);
        if let Some(err) = err {
            errs.push(err);
        }

        (input, o, errs)
    }
}

#[cfg(all(test, feature = "ascii", feature = "binary"))]
mod tests {
    use super::*;

    use snapbox::prelude::*;
    use snapbox::str;

    use crate::binary::be_u16;
    use crate::error::ErrMode;
    use crate::error::Needed;
    use crate::error::TestResult;
    use crate::token::take;
    use crate::Partial;

    #[doc(hidden)]
    #[macro_export]
    macro_rules! assert_size (
        ($t:ty, $sz:expr) => (
            assert!(core::mem::size_of::<$t>() <= $sz, "{} <= {} failed", core::mem::size_of::<$t>(), $sz);
        );
    );

    #[test]
    #[cfg(target_pointer_width = "64")]
    fn size_test() {
        assert_size!(Result<&[u8], (&[u8], u32)>, 40);
        assert_size!(Result<&str, u32>, 40);
        assert_size!(Needed, 8);
        assert_size!(ErrMode<u32>, 16);
    }

    #[test]
    fn err_map_test() {
        let e = ErrMode::Backtrack(1);
        assert_eq!(e.map(|v| v + 1), ErrMode::Backtrack(2));
    }

    #[test]
    fn single_element_tuples() {
        use crate::ascii::alpha1;

        let mut parser = (alpha1,);
        assert_parse!(
            parser.parse_peek("abc123def"),
            str![[r#"
Ok(
    (
        "123def",
        (
            "abc",
        ),
    ),
)

"#]]
            .raw()
        );
        assert_parse!(
            parser.parse_peek("123def"),
            str![[r#"
Err(
    Backtrack(
        InputError {
            input: "123def",
        },
    ),
)

"#]]
            .raw()
        );
    }

    #[test]
    fn tuple_test() {
        #[allow(clippy::type_complexity)]
        fn tuple_3<'i>(
            i: &mut Partial<&'i [u8]>,
        ) -> TestResult<Partial<&'i [u8]>, (u16, &'i [u8], &'i [u8])> {
            (be_u16, take(3u8), "fg").parse_next(i)
        }

        assert_parse!(
            tuple_3.parse_peek(Partial::new(&b"abcdefgh"[..])),
            str![[r#"
Ok(
    (
        Partial {
            input: [
                104,
            ],
            partial: true,
        },
        (
            24930,
            [
                99,
                100,
                101,
            ],
            [
                102,
                103,
            ],
        ),
    ),
)

"#]]
            .raw()
        );
        assert_parse!(
            tuple_3.parse_peek(Partial::new(&b"abcd"[..])),
            str![[r#"
Err(
    Incomplete(
        Size(
            1,
        ),
    ),
)

"#]]
            .raw()
        );
        assert_parse!(
            tuple_3.parse_peek(Partial::new(&b"abcde"[..])),
            str![[r#"
Err(
    Incomplete(
        Unknown,
    ),
)

"#]]
            .raw()
        );
        assert_parse!(
            tuple_3.parse_peek(Partial::new(&b"abcdejk"[..])),
            str![[r#"
Err(
    Backtrack(
        InputError {
            input: Partial {
                input: [
                    106,
                    107,
                ],
                partial: true,
            },
        },
    ),
)

"#]]
            .raw()
        );
    }

    #[test]
    fn unit_type() {
        fn parser<'i>(i: &mut &'i str) -> TestResult<&'i str, ()> {
            ().parse_next(i)
        }
        assert_parse!(
            parser.parse_peek("abxsbsh"),
            str![[r#"
Ok(
    (
        "abxsbsh",
        (),
    ),
)

"#]]
            .raw()
        );
        assert_parse!(
            parser.parse_peek("sdfjakdsas"),
            str![[r#"
Ok(
    (
        "sdfjakdsas",
        (),
    ),
)

"#]]
            .raw()
        );
        assert_parse!(
            parser.parse_peek(""),
            str![[r#"
Ok(
    (
        "",
        (),
    ),
)

"#]]
            .raw()
        );
    }
}