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#![doc = include_str!("../README.md")]
#![deny(missing_docs)]
#![allow(deprecated)] // TODO: Don't allow this
// TODO: Enable when stable
//#![feature(once_cell)]
/// Utilities for debugging parsers.
pub mod debug;
/// Combinators that allow combining and extending existing parsers.
pub mod combinator;
/// Error types, traits and utilities.
pub mod error;
/// Traits that allow chaining parser outputs together.
pub mod chain;
/// Parser primitives that accept specific token patterns.
pub mod primitive;
/// Types and traits that facilitate error recovery.
pub mod recovery;
/// Recursive parsers (parser that include themselves within their patterns).
pub mod recursive;
/// Types and traits related to spans.
pub mod span;
/// Token streams and behaviours.
pub mod stream;
/// Text-specific parsers and utilities.
pub mod text;
pub use crate::{
error::Error,
span::Span,
};
pub use crate::{
stream::{Stream, BoxStream, Flat},
};
use crate::{
chain::Chain,
combinator::*,
primitive::*,
recovery::*,
debug::*,
};
use std::{
marker::PhantomData,
rc::Rc,
cmp::Ordering,
ops::Range,
// TODO: Enable when stable
//lazy::OnceCell,
fmt,
};
/// Commonly used functions, traits and types.
pub mod prelude {
pub use super::{
error::{Error as _, Simple},
text::TextParser as _,
span::Span as _,
primitive::{any, end, filter, filter_map, just, one_of, none_of, seq},
recovery::{skip_then_retry_until, nested_delimiters},
recursive::recursive,
text,
Parser,
BoxedParser,
};
}
// TODO: Replace with `std::ops::ControlFlow` when stable
enum ControlFlow<C, B> {
Continue(C),
Break(B),
}
/// An internal type used to facilitate error prioritisation. You shouldn't need to interact with this type during
/// normal use of the crate.
pub struct Located<I, E> {
at: usize,
error: E,
phantom: PhantomData<I>,
}
impl<I, E: Error<I>> Located<I, E> {
/// Create a new [`Located`] with the give input position and error.
pub fn at(at: usize, error: E) -> Self {
Self { at, error, phantom: PhantomData }
}
/// Get the maximum of two located errors. If they hold the same position in the input, merge them.
pub fn max(self, other: impl Into<Option<Self>>) -> Self {
let other = match other.into() {
Some(other) => other,
None => return self,
};
match self.at.cmp(&other.at) {
Ordering::Greater => self,
Ordering::Less => other,
Ordering::Equal => Self {
error: self.error.merge(other.error),
..self
},
}
}
/// Map the error with the given function.
pub fn map<U, F: FnOnce(E) -> U>(self, f: F) -> Located<I, U> {
Located {
at: self.at,
error: f(self.error),
phantom: PhantomData,
}
}
}
// Merge two alternative errors
// TODO: Allow multiple alternative errors
fn merge_alts<I, E: Error<I>>(a: Option<Located<I, E>>, b: Option<Located<I, E>>) -> Option<Located<I, E>> {
match (a, b) {
(Some(a), Some(b)) => Some(a.max(b)),
(a, b) => a.or(b),
}
}
// ([], Ok((out, recovered, alt_err))) => parsing successful, recovered = whether the false is a false recovered value,
// alt_err = potential alternative error should a different number of optional patterns be parsed
// ([x, ...], Ok(out)) => parsing failed, but recovery occurred so parsing may continue
// ([...], Err(err)) => parsing failed, recovery failed, and one or more errors were produced
// TODO: Change `alt_err` from `Option<Located<I, E>>` to `Vec<Located<I, E>>`
type PResult<I, O, E> = (Vec<Located<I, E>>, Result<(O, Option<Located<I, E>>), Located<I, E>>);
// Shorthand for a stream with the given input and error type.
type StreamOf<'a, I, E> = Stream<'a, I, <E as Error<I>>::Span>;
// [`Parser::parse_recovery`], but generic across the debugger.
fn parse_recovery_inner<
'a,
I: Clone,
O,
P: Parser<I, O>,
D: Debugger,
Iter: Iterator<Item = (I, <P::Error as Error<I>>::Span)> + 'a,
S: Into<Stream<'a, I, <P::Error as Error<I>>::Span, Iter>>,
>(parser: &P, debugger: &mut D, stream: S) -> (Option<O>, Vec<P::Error>) where P: Sized {
#[allow(deprecated)]
let (mut errors, res) = parser.parse_inner(debugger, &mut stream.into());
let out = match res {
Ok((out, _)) => Some(out),
Err(err) => {
errors.push(err);
None
},
};
(out, errors.into_iter().map(|e| e.error).collect())
}
/// A trait implemented by parsers.
///
/// Parsers take a stream of tokens of type `I` and attempt to parse them into a value of type `O`. In doing so, they
/// may encounter errors. These need not be fatal to the parsing process: syntactic errors can be recovered from and a
/// valid output may still be generated alongside any syntax errors that were encountered along the way. Usually, this
/// output comes in the form of an [Abstract Syntax Tree](https://en.wikipedia.org/wiki/Abstract_syntax_tree) (AST).
pub trait Parser<I: Clone, O> {
/// The type of errors emitted by this parser.
type Error: Error<I>; // TODO when default associated types are stable: = Cheap<I>;
/// Parse a stream with all the bells & whistles. You can use this to implement your own parser combinators. Note
/// that both the signature and semantic requirements of this function are very likely to change in later versions.
/// Where possible, prefer more ergonomic combinators provided elsewhere in the crate rather than implementing your
/// own. For example, [`custom`] provides a flexible, ergonomic way API for process input streams that likely
/// covers your use-case.
#[deprecated(note = "This method is excluded from the semver guarantees of chumsky. If you decide to use it, broken builds are your fault.")]
fn parse_inner<D: Debugger>(&self, debugger: &mut D, stream: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> where Self: Sized;
/// [`Parser::parse_inner`], but specialised for verbose output. Do not call this method directly.
///
/// If you *really* need to implement this trait, this method should just directly invoke [`Parser::parse_inner`].
#[deprecated(note = "This method is excluded from the semver guarantees of chumsky. If you decide to use it, broken builds are your fault.")]
fn parse_inner_verbose(&self, d: &mut Verbose, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error>;
/// [`Parser::parse_inner`], but specialised for silent output. Do not call this method directly.
///
/// If you *really* need to implement this trait, this method should just directly invoke [`Parser::parse_inner`].
#[deprecated(note = "This method is excluded from the semver guarantees of chumsky. If you decide to use it, broken builds are your fault.")]
fn parse_inner_silent(&self, d: &mut Silent, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error>;
/// Parse a stream of tokens, yielding an output if possible, and any errors encountered along the way.
///
/// If you don't care about producing an output if errors are encountered, use `Parser::parse` instead.
fn parse_recovery<
'a,
Iter: Iterator<Item = (I, <Self::Error as Error<I>>::Span)> + 'a,
S: Into<Stream<'a, I, <Self::Error as Error<I>>::Span, Iter>>,
>(&self, stream: S) -> (Option<O>, Vec<Self::Error>) where Self: Sized {
parse_recovery_inner(self, &mut Silent::new(), stream)
}
/// Parse a stream of tokens, yielding an output if possible, and any errors encountered along the way. Unlike
/// [`Parser::parse_recovery`], this function will produce verbose debugging output as it executes.
///
/// If you don't care about producing an output if errors are encountered, use `Parser::parse` instead.
///
/// You'll probably want to make sure that this doesn't end up in production code: it exists only to help you debug
/// your parser. Additionally, its API is quite likely to change in future versions.
fn parse_recovery_verbose<
'a,
Iter: Iterator<Item = (I, <Self::Error as Error<I>>::Span)> + 'a,
S: Into<Stream<'a, I, <Self::Error as Error<I>>::Span, Iter>>,
>(&self, stream: S) -> (Option<O>, Vec<Self::Error>) where Self: Sized {
let mut debugger = Verbose::new();
let res = parse_recovery_inner(self, &mut debugger, stream);
debugger.print();
res
}
/// Parse a stream of tokens, yielding an output *or* any errors that were encountered along the way.
///
/// If you wish to attempt to produce an output even if errors are encountered, use `Parser::parse_recovery`.
fn parse<
'a,
Iter: Iterator<Item = (I, <Self::Error as Error<I>>::Span)> + 'a,
S: Into<Stream<'a, I, <Self::Error as Error<I>>::Span, Iter>>,
>(&self, stream: S) -> Result<O, Vec<Self::Error>> where Self: Sized {
let (output, errors) = self.parse_recovery(stream);
if errors.is_empty() {
Ok(output.expect("Parsing failed, but no errors were emitted. This is troubling, to say the least."))
} else {
Err(errors)
}
}
/// Include this parser in the debugging output produced by [`Parser::parse_recovery_verbose`].
///
/// You'll probably want to make sure that this doesn't end up in production code: it exists only to help you debug
/// your parser. Additionally, its API is quite likely to change in future versions.
#[track_caller]
fn debug<T: fmt::Display + 'static>(self, x: T) -> Debug<Self> where Self: Sized {
Debug(self, Rc::new(x), *std::panic::Location::caller())
}
/// Map the output of this parser to aanother value.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// #[derive(Debug, PartialEq)]
/// enum Token { Word(String), Num(u64) }
///
/// let word = filter::<_, _, Cheap<char>>(|c: &char| c.is_alphabetic())
/// .repeated().at_least(1)
/// .collect::<String>()
/// .map(Token::Word);
///
/// let num = filter::<_, _, Cheap<char>>(|c: &char| c.is_ascii_digit())
/// .repeated().at_least(1)
/// .collect::<String>()
/// .map(|s| Token::Num(s.parse().unwrap()));
///
/// let token = word.or(num);
///
/// assert_eq!(token.parse("test"), Ok(Token::Word("test".to_string())));
/// assert_eq!(token.parse("42"), Ok(Token::Num(42)));
/// ```
fn map<U, F: Fn(O) -> U>(self, f: F) -> Map<Self, F, O> where Self: Sized { Map(self, f, PhantomData) }
/// Map the output of this parser to another value, making use of the pattern's overall span.
///
/// This is very useful when generating an AST but you need to know what span to give each AST node.
fn map_with_span<U, F: Fn(O, <Self::Error as Error<I>>::Span) -> U>(self, f: F) -> MapWithSpan<Self, F, O>
where Self: Sized
{ MapWithSpan(self, f, PhantomData) }
/// Map the primary error of this parser to another value.
///
/// This function is most useful when using a custom error type, allowing you to augment errors according to
/// context.
fn map_err<F: Fn(Self::Error) -> Self::Error>(self, f: F) -> MapErr<Self, F>
where Self: Sized
{ MapErr(self, f) }
/// After a successful parse, apply a fallible function to the output. If the function produces an error, treat it
/// as a parsing error.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let byte = text::int::<_, Simple<char>>(10)
/// .try_map(|s, span| s
/// .parse::<u8>()
/// .map_err(|e| Simple::custom(span, format!("{}", e))));
///
/// assert!(byte.parse("255").is_ok());
/// assert!(byte.parse("256").is_err()); // Out of range
/// ```
fn try_map<U, F: Fn(O, <Self::Error as Error<I>>::Span) -> Result<U, Self::Error>>(self, f: F) -> TryMap<Self, F, O>
where Self: Sized
{ TryMap(self, f, PhantomData) }
/// Label the pattern parsed by this parser for more useful error messages.
///
/// This is useful when you want to give users a more useful description of an expected pattern than simply a list
/// of possible initial tokens. For example, it's common to use the term "expression" at a catch-all for a number
/// of different constructs in many languages.
///
/// This does not label recovered errors generated by sub-patterns within the parser, only error *directly* emitted
/// by the parser.
///
/// This does not label errors where the labelled pattern consumed input (i.e: in unambiguous cases).
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let frac = text::digits(10)
/// .chain(just('.'))
/// .chain::<char, _, _>(text::digits(10))
/// .collect::<String>()
/// .then_ignore(end())
/// .labelled("number");
///
/// assert_eq!(frac.parse("42.3"), Ok("42.3".to_string()));
/// assert_eq!(frac.parse("hello"), Err(vec![Cheap::expected_input_found(0..1, None, Some('h')).with_label("number")]));
/// assert_eq!(frac.parse("42!"), Err(vec![Cheap::expected_input_found(2..3, Some('.'), Some('!')).with_label("number")]));
/// ```
fn labelled<L: Into<<Self::Error as Error<I>>::Label> + Clone>(self, label: L) -> Label<Self, L>
where Self: Sized
{ Label(self, label) }
/// Transform all outputs of this parser to a pretermined value.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// #[derive(Clone, Debug, PartialEq)]
/// enum Op { Add, Sub, Mul, Div }
///
/// let op = just::<_, Cheap<char>>('+').to(Op::Add)
/// .or(just('-').to(Op::Sub))
/// .or(just('*').to(Op::Mul))
/// .or(just('/').to(Op::Div));
///
/// assert_eq!(op.parse("+"), Ok(Op::Add));
/// assert_eq!(op.parse("/"), Ok(Op::Div));
/// ```
fn to<U: Clone>(self, x: U) -> To<Self, O, U> where Self: Sized { To(self, x, PhantomData) }
/// Left-fold the output of the parser into a single value, where the output is of type `(_, Vec<_>)`.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let int = text::int::<char, Cheap<char>>(10)
/// .map(|s| s.parse().unwrap());
///
/// let sum = int
/// .then(just('+').ignore_then(int).repeated())
/// .foldl(|a, b| a + b);
///
/// assert_eq!(sum.parse("1+12+3+9"), Ok(25));
/// assert_eq!(sum.parse("6"), Ok(6));
/// ```
fn foldl<A, B, F: Fn(A, B) -> A>(self, f: F) -> Foldl<Self, F, A, B>
where
Self: Parser<I, (A, Vec<B>)> + Sized
{ Foldl(self, f, PhantomData) }
/// Right-fold the output of the parser into a single value, where the output is of type `(Vec<_>, _)`.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let int = text::int::<char, Cheap<char>>(10)
/// .map(|s| s.parse().unwrap());
///
/// let signed = just('+').to(1)
/// .or(just('-').to(-1))
/// .repeated()
/// .then(int)
/// .foldr(|a, b| a * b);
///
/// assert_eq!(signed.parse("3"), Ok(3));
/// assert_eq!(signed.parse("-17"), Ok(-17));
/// assert_eq!(signed.parse("--+-+-5"), Ok(5));
/// ```
fn foldr<'a, A, B, F: Fn(A, B) -> B + 'a>(self, f: F) -> Foldr<Self, F, A, B>
where
Self: Parser<I, (Vec<A>, B)> + Sized
{ Foldr(self, f, PhantomData) }
/// Ignore the output of this parser, yielding `()` as an output instead.
///
/// This can be used to reduce the cost of parsing by avoiding unnecessary allocations (most collections containing
/// [ZSTs](https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts) do
/// [not allocate](https://doc.rust-lang.org/std/vec/struct.Vec.html#guarantees)). For example, it's common to want
/// to ignore whitespace in many grammars.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// // A parser that parses any number of whitespace characters without allocating
/// let whitespace = filter::<_, _, Cheap<char>>(|c: &char| c.is_whitespace())
/// .ignored()
/// .repeated();
///
/// assert_eq!(whitespace.parse(" "), Ok(vec![(); 4]));
/// assert_eq!(whitespace.parse(" hello"), Ok(vec![(); 2]));
/// ```
fn ignored(self) -> Ignored<Self, O> where Self: Sized { To(self, (), PhantomData) }
/// Collect the output of this parser into a collection.
///
/// This is commonly useful for collecting [`Vec<char>`] outputs into [`String`]s.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let word = filter::<_, _, Cheap<char>>(|c: &char| c.is_alphabetic())
/// .repeated()
/// .collect::<String>();
///
/// assert_eq!(word.parse("hello"), Ok("hello".to_string()));
/// ```
fn collect<C: core::iter::FromIterator<O::Item>>(self) -> Map<Self, fn(O) -> C, O>
where Self: Sized, O: IntoIterator
{ self.map(|items| C::from_iter(items.into_iter())) }
/// Parse one thing and then another thing, yielding a tuple of the two outputs.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let word = filter::<_, _, Cheap<char>>(|c: &char| c.is_alphabetic())
/// .repeated().at_least(1)
/// .collect::<String>();
/// let two_words = word.then_ignore(just(' ')).then(word);
///
/// assert_eq!(two_words.parse("dog cat"), Ok(("dog".to_string(), "cat".to_string())));
/// assert!(two_words.parse("hedgehog").is_err());
/// ```
fn then<U, P: Parser<I, U>>(self, other: P) -> Then<Self, P> where Self: Sized { Then(self, other) }
/// Parse one thing and then another thing, attempting to chain the two outputs into a [`Vec`].
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let int = just('-').or_not()
/// .chain(filter::<_, _, Cheap<char>>(|c: &char| c.is_ascii_digit() && *c != '0')
/// .chain(filter::<_, _, Cheap<char>>(|c: &char| c.is_ascii_digit()).repeated()))
/// .or(just('0').map(|c| vec![c]))
/// .then_ignore(end())
/// .collect::<String>()
/// .map(|s| s.parse().unwrap());
///
/// assert_eq!(int.parse("0"), Ok(0));
/// assert_eq!(int.parse("415"), Ok(415));
/// assert_eq!(int.parse("-50"), Ok(-50));
/// assert!(int.parse("-0").is_err());
/// assert!(int.parse("05").is_err());
/// ```
fn chain<T, U, P: Parser<I, U, Error = Self::Error>>(self, other: P) -> Map<Then<Self, P>, fn((O, U)) -> Vec<T>, (O, U)>
where
Self: Sized,
U: Chain<T>,
O: Chain<T>,
{
self.then(other).map(|(a, b)| {
let mut v = Vec::with_capacity(a.len() + b.len());
a.append_to(&mut v);
b.append_to(&mut v);
v
})
}
/// Flatten a nested collection.
///
/// This use-cases of this method are broadly similar to those of [`Iterator::flatten`].
fn flatten<T, Inner>(self) -> Map<Self, fn(O) -> Vec<T>, O>
where
Self: Sized,
O: IntoIterator<Item = Inner>,
Inner: IntoIterator<Item = T>,
{ self.map(|xs| xs.into_iter().map(|xs| xs.into_iter()).flatten().collect()) }
/// Parse one thing and then another thing, yielding only the output of the latter.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let zeroes = filter::<_, _, Cheap<char>>(|c: &char| *c == '0').ignored().repeated();
/// let digits = filter(|c: &char| c.is_ascii_digit()).repeated();
/// let integer = zeroes
/// .ignore_then(digits)
/// .collect::<String>()
/// .map(|s| s.parse().unwrap());
///
/// assert_eq!(integer.parse("00064"), Ok(64));
/// assert_eq!(integer.parse("32"), Ok(32));
/// ```
fn ignore_then<U, P: Parser<I, U>>(self, other: P) -> IgnoreThen<Self, P, O, U>
where Self: Sized
{ Map(Then(self, other), |(_, u)| u, PhantomData) }
/// Parse one thing and then another thing, yielding only the output of the former.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let word = filter::<_, _, Cheap<char>>(|c: &char| c.is_alphabetic())
/// .repeated().at_least(1)
/// .collect::<String>();
///
/// let punctuated = word
/// .then_ignore(just('!').or(just('?')).or_not());
///
/// let sentence = punctuated
/// .padded() // Allow for whitespace gaps
/// .repeated();
///
/// assert_eq!(
/// sentence.parse("hello! how are you?"),
/// Ok(vec![
/// "hello".to_string(),
/// "how".to_string(),
/// "are".to_string(),
/// "you".to_string(),
/// ]),
/// );
/// ```
fn then_ignore<U, P: Parser<I, U>>(self, other: P) -> ThenIgnore<Self, P, O, U>
where Self: Sized
{ Map(Then(self, other), |(o, _)| o, PhantomData) }
/// Parse a pattern, but with an instance of another pattern on either end, yielding the output of the inner.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let ident = text::ident::<_, Simple<char>>()
/// .padded_by(just('!'));
///
/// assert_eq!(ident.parse("!hello!"), Ok("hello".to_string()));
/// assert!(ident.parse("hello!").is_err());
/// assert!(ident.parse("!hello").is_err());
/// assert!(ident.parse("hello").is_err());
/// ```
fn padded_by<U, P: Parser<I, U, Error = Self::Error> + Clone>(self, other: P) -> ThenIgnore<IgnoreThen<P, Self, U, O>, P, O, U>
where Self: Sized
{ other.clone().ignore_then(self).then_ignore(other) }
// fn then_catch(self, end: I) -> ThenCatch<Self, I> where Self: Sized { ThenCatch(self, end) }
/// Parse the pattern surrounded by the given delimiters.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// // A LISP-style S-expression
/// #[derive(Debug, PartialEq)]
/// enum SExpr {
/// Ident(String),
/// Num(u64),
/// List(Vec<SExpr>),
/// }
///
/// let ident = filter::<_, _, Cheap<char>>(|c: &char| c.is_alphabetic())
/// .repeated().at_least(1)
/// .collect::<String>();
///
/// let num = text::int(10)
/// .map(|s: String| s.parse().unwrap());
///
/// let s_expr = recursive(|s_expr| s_expr
/// .padded()
/// .repeated()
/// .map(SExpr::List)
/// .delimited_by('(', ')')
/// .or(ident.map(SExpr::Ident))
/// .or(num.map(SExpr::Num)));
///
/// // A valid input
/// assert_eq!(
/// s_expr.parse_recovery("(add (mul 42 3) 15)"),
/// (
/// Some(SExpr::List(vec![
/// SExpr::Ident("add".to_string()),
/// SExpr::List(vec![
/// SExpr::Ident("mul".to_string()),
/// SExpr::Num(42),
/// SExpr::Num(3),
/// ]),
/// SExpr::Num(15),
/// ])),
/// Vec::new(), // No errors!
/// ),
/// );
/// ```
fn delimited_by(self, start: I, end: I) -> DelimitedBy<Self, I> where Self: Sized { DelimitedBy(self, start, end) }
/// Parse one thing or, on failure, another thing.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let op = just::<_, Cheap<char>>('+')
/// .or(just('-'))
/// .or(just('*'))
/// .or(just('/'));
///
/// assert_eq!(op.parse("+"), Ok('+'));
/// assert_eq!(op.parse("/"), Ok('/'));
/// assert!(op.parse("!").is_err());
/// ```
fn or<P: Parser<I, O>>(self, other: P) -> Or<Self, P> where Self: Sized { Or(self, other) }
/// Apply a fallback recovery strategy to this parser should it fail.
///
/// There is no silver bullet for error recovery, so this function allows you to specify one of several different
/// strategies at the location of your choice.
///
/// Note that for implementation reasons, adding an error recovery strategy can cause a parser to 'over-commit',
/// missing potentially valid alternative parse routes (*TODO: document this and explain why and when it happens*).
/// Rest assured that this case is generally quite rare and only happens for very loose, almost-ambiguous syntax.
/// If you run into cases that you believe should parse but do not, try removing or moving recovery strategies to
/// fix the problem.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// #[derive(Debug, PartialEq)]
/// enum Expr {
/// Error,
/// Int(String),
/// List(Vec<Expr>),
/// }
///
/// let expr = recursive::<_, _, _, _, Simple<char>>(|expr| expr
/// .separated_by(just(','))
/// .delimited_by('[', ']')
/// .map(Expr::List)
/// // If parsing a list expression fails, recover at the next delimiter, generating an error AST node
/// .recover_with(nested_delimiters('[', ']', [], || Expr::Error))
/// .or(text::int(10).map(Expr::Int))
/// .padded());
///
/// assert!(expr.parse("five").is_err()); // Text is not a valid expression in this language...
/// assert!(expr.parse("[1, 2, 3]").is_ok()); // ...but lists and numbers are!
///
/// // This input has two syntax errors...
/// let (ast, errors) = expr.parse_recovery("[[1, two], [3, four]]");
/// // ...and error recovery allows us to catch both of them!
/// assert_eq!(errors.len(), 2);
/// // Additionally, the AST we get back still has useful information.
/// assert_eq!(ast, Some(Expr::List(vec![Expr::Error, Expr::Error])));
/// ```
fn recover_with<S: Strategy<I, O>>(self, strategy: S) -> Recovery<Self, S> where Self: Sized {
Recovery(self, strategy)
}
/// Attempt to parse something, but only if it exists.
///
/// If parsing of the pattern is successful, the output is `Some(_)`. Otherwise, the output is `None`.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let word = filter::<_, _, Cheap<char>>(|c: &char| c.is_alphabetic())
/// .repeated().at_least(1)
/// .collect::<String>();
///
/// let word_or_question = word
/// .then(just('?').or_not());
///
/// assert_eq!(word_or_question.parse("hello?"), Ok(("hello".to_string(), Some('?'))));
/// assert_eq!(word_or_question.parse("wednesday"), Ok(("wednesday".to_string(), None)));
/// ```
fn or_not(self) -> OrNot<Self> where Self: Sized { OrNot(self) }
/// Parse an expression any number of times (including zero times).
///
/// Input is eagerly parsed. Be aware that the parser will accept no occurences of the pattern too. Consider using
/// [`Parser::repeated().at_least`] instead if it better suits your use-case.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let num = filter::<_, _, Cheap<char>>(|c: &char| c.is_ascii_digit())
/// .repeated().at_least(1)
/// .collect::<String>()
/// .map(|s| s.parse().unwrap());
///
/// let sum = num.then(just('+').ignore_then(num).repeated())
/// .foldl(|a, b| a + b);
///
/// assert_eq!(sum.parse("2+13+4+0+5"), Ok(24));
/// ```
fn repeated(self) -> Repeated<Self> where Self: Sized { Repeated(self, 0, None) }
/// Parse an expression, separated by another, any number of times.
///
/// You can use [`SeparatedBy::allow_leading`] or [`SeparatedBy::allow_trailing`] to allow leading or trailing
/// separators.
///
/// # Examples
///
/// ```
/// # use chumsky::{prelude::*, error::Cheap};
///
/// let shopping = text::ident::<_, Simple<char>>()
/// .padded()
/// .separated_by(just(','));
///
/// assert_eq!(shopping.parse("eggs"), Ok(vec!["eggs".to_string()]));
/// assert_eq!(shopping.parse("eggs, flour, milk"), Ok(vec!["eggs".to_string(), "flour".to_string(), "milk".to_string()]));
/// ```
///
/// See [`SeparatedBy::allow_leading`] and [`SeparatedBy::allow_trailing`] for more examples.
fn separated_by<U, P: Parser<I, U>>(self, other: P) -> SeparatedBy<Self, P, U> where Self: Sized {
SeparatedBy {
a: self,
b: other,
at_least: 0,
allow_leading: false,
allow_trailing: false,
phantom: PhantomData,
}
}
/// Box the parser, yielding a parser that performs parsing through dynamic dispatch.
///
/// Boxing a parser might be useful for:
///
/// - Passing a parser over an FFI boundary
///
/// - Getting around compiler implementation problems with long types such as
/// [this](https://github.com/rust-lang/rust/issues/54540).
///
/// - Places where you need to name the type of a parser
///
/// Boxing a parser is broadly equivalent to boxing other combinators, such as [`Iterator`].
fn boxed<'a>(self) -> BoxedParser<'a, I, O, Self::Error> where Self: Sized + 'a {
BoxedParser(Rc::new(self))
}
}
impl<'a, I: Clone, O, T: Parser<I, O> + ?Sized> Parser<I, O> for &'a T {
type Error = T::Error;
fn parse_inner<D: Debugger>(&self, debugger: &mut D, stream: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> {
debugger.invoke::<_, _, T>(*self, stream)
}
fn parse_inner_verbose(&self, d: &mut Verbose, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
fn parse_inner_silent(&self, d: &mut Silent, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
}
impl<I: Clone, O, T: Parser<I, O> + ?Sized> Parser<I, O> for Box<T> {
type Error = T::Error;
fn parse_inner<D: Debugger>(&self, debugger: &mut D, stream: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> {
debugger.invoke::<_, _, T>(&*self, stream)
}
fn parse_inner_verbose(&self, d: &mut Verbose, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
fn parse_inner_silent(&self, d: &mut Silent, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
}
impl<I: Clone, O, T: Parser<I, O> + ?Sized> Parser<I, O> for Rc<T> {
type Error = T::Error;
fn parse_inner<D: Debugger>(&self, debugger: &mut D, stream: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> {
debugger.invoke::<_, _, T>(&*self, stream)
}
fn parse_inner_verbose(&self, d: &mut Verbose, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
fn parse_inner_silent(&self, d: &mut Silent, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
}
/// See [`Parser::boxed`].
///
/// This type is a [`repr(transparent)`](https://doc.rust-lang.org/nomicon/other-reprs.html#reprtransparent) wrapper
/// around its inner value.
///
/// Due to current implementation details, the inner value is not, in fact, a [`Box`], but is an [`Rc`] to facilitate
/// efficient cloning. This is likely to change in the future. Unlike [`Box`], [`Rc`] has no size guarantees: although
/// it is *currently* the same size as a raw pointer.
// TODO: Don't use an Rc
#[repr(transparent)]
pub struct BoxedParser<'a, I, O, E: Error<I>>(Rc<dyn Parser<I, O, Error = E> + 'a>);
impl<'a, I, O, E: Error<I>> Clone for BoxedParser<'a, I, O, E> {
fn clone(&self) -> Self { Self(self.0.clone()) }
}
impl<'a, I: Clone, O, E: Error<I>> Parser<I, O> for BoxedParser<'a, I, O, E> {
type Error = E;
fn parse_inner<D: Debugger>(&self, debugger: &mut D, stream: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> {
#[allow(deprecated)]
debugger.invoke(&self.0, stream)
}
fn parse_inner_verbose(&self, d: &mut Verbose, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
fn parse_inner_silent(&self, d: &mut Silent, s: &mut StreamOf<I, Self::Error>) -> PResult<I, O, Self::Error> { #[allow(deprecated)] self.parse_inner(d, s) }
}