css_parse/traits/
parse.rs

1use crate::{Cursor, Parser, Peek, Result};
2use bumpalo::collections::Vec;
3
4/// This trait allows AST nodes to construct themselves from a mutable [Parser] instance.
5///
6/// Nodes that implement this trait are entitled to consume any number of [Cursors][crate::Cursor] from [Parser] in
7/// order to construct themselves. They may also consume some amount of tokens and still return an [Err] - there is no
8/// need to try and reset the [Parser] state on failure ([Parser::try_parse()] exists for this reason).
9///
10/// When wanting to parse child nodes, implementations should _not_ call [Parse::parse()] directly. Instead - call
11/// [`Parser::parse<T>()`]. Other convenience methods such as [`Parser::parse_if_peek<T>()`] and [`Parser::try_parse<T>()`]
12/// exist.
13///
14/// Any node implementing [Parse::parse()] gets [Parse::try_parse()] for free. It's unlikely that nodes can come up with
15/// a more efficient algorithm than the provided one, so it is not worth re-implementing [Parse::try_parse()].
16///
17/// If a Node can construct itself from a single [Cursor][crate::Cursor] it should implement
18/// [Peek][crate::Peek] and [Parse], where [Parse::parse()] calls [Parser::next()] and constructs from the cursor.
19pub trait Parse<'a>: Sized {
20	fn parse<I>(p: &mut Parser<'a, I>) -> Result<Self>
21	where
22		I: Iterator<Item = Cursor> + Clone;
23
24	fn try_parse<I>(p: &mut Parser<'a, I>) -> Result<Self>
25	where
26		I: Iterator<Item = Cursor> + Clone,
27	{
28		let checkpoint = p.checkpoint();
29		Self::parse(p).inspect_err(|_| p.rewind(checkpoint))
30	}
31}
32
33impl<'a, T> Parse<'a> for Option<T>
34where
35	T: Peek<'a> + Parse<'a>,
36{
37	fn parse<Iter>(p: &mut Parser<'a, Iter>) -> Result<Self>
38	where
39		Iter: Iterator<Item = Cursor> + Clone,
40	{
41		p.parse_if_peek::<T>()
42	}
43}
44
45impl<'a, T> Parse<'a> for Vec<'a, T>
46where
47	T: Peek<'a> + Parse<'a>,
48{
49	fn parse<Iter>(p: &mut Parser<'a, Iter>) -> Result<Self>
50	where
51		Iter: Iterator<Item = Cursor> + Clone,
52	{
53		let mut vec = Vec::new_in(p.bump());
54		while let Some(item) = p.parse_if_peek::<T>()? {
55			vec.push(item);
56		}
57		Ok(vec)
58	}
59}
60
61macro_rules! impl_tuple {
62    ($($T:ident),*) => {
63        impl<'a, $($T),*> Parse<'a> for ($($T),*)
64        where
65            $($T: Parse<'a>),*
66        {
67            #[allow(non_snake_case)]
68            #[allow(unused)]
69            fn parse<Iter>(p: &mut Parser<'a, Iter>) -> Result<Self>
70            where
71                Iter: Iterator<Item = Cursor> + Clone,
72            {
73                $(let $T = p.parse::<$T>()?;)*
74                Ok(($($T),*))
75            }
76        }
77    };
78}
79
80impl_tuple!(A, B);
81impl_tuple!(A, B, C);
82impl_tuple!(A, B, C, D);
83impl_tuple!(A, B, C, D, E);
84impl_tuple!(A, B, C, D, E, F);
85impl_tuple!(A, B, C, D, E, F, G);
86impl_tuple!(A, B, C, D, E, F, G, H);
87impl_tuple!(A, B, C, D, E, F, G, H, I);
88impl_tuple!(A, B, C, D, E, F, G, H, I, J);
89impl_tuple!(A, B, C, D, E, F, G, H, I, J, K);
90impl_tuple!(A, B, C, D, E, F, G, H, I, J, K, L);
css_parse/traits/parse.rs

css_parse/traits/
parse.rs
