rustyfi_syntax/
stream.rs

1//! The parse source for the SATySFi surface grammar.
2//!
3//! The parse source is the eagerly lexed `Vec<Atom>`, wrapped by
4//! [`AtomStream`]: syan core has no `IntoParseStream for Vec<_>`, so the
5//! buffering lives here.
6//!
7//! Neither stream erasure (a `&mut dyn ParseStream` tower) nor a failure
8//! high-water mark belongs here, obsoleted by syan on both counts:
9//! `Parse::parse_stream` takes `&mut S` and recursion reborrows, so `S` is a
10//! genuine fixed point and the instantiation set is finite without erasing
11//! anything (and no stream operation is a virtual call); and `ParseError` is
12//! span-generic, every variant carrying the position it failed at, so the
13//! error reports itself.
14
15use crate::token::Atom;
16use std::convert::Infallible;
17use syan::parse::tape::Tape;
18use syan::parse::ParseStream;
19
20/// A parse source over an eagerly lexed token vector.
21///
22/// Backtracking runs through syan's [`Tape`], which owns the pushback and the
23/// checkpoint scopes, so this is a thin forwarding shim and nothing more.
24pub struct AtomStream {
25    tape: Tape<std::vec::IntoIter<Atom>>,
26}
27
28impl AtomStream {
29    pub fn new(atoms: Vec<Atom>) -> Self {
30        AtomStream {
31            tape: Tape::new(atoms.into_iter()),
32        }
33    }
34}
35
36impl ParseStream for AtomStream {
37    type Atom = Atom;
38    type Error = Infallible;
39
40    fn next(&mut self) -> Option<Self::Atom> {
41        self.tape.next()
42    }
43
44    fn peek(&mut self) -> Option<&Self::Atom> {
45        self.tape.peek()
46    }
47
48    fn push(&mut self, atom: Self::Atom) {
49        self.tape.push(atom);
50    }
51
52    fn checkpoint_raw(&mut self) -> u64 {
53        self.tape.checkpoint()
54    }
55
56    fn rollback_raw(&mut self, raw: u64) {
57        self.tape.rollback(raw);
58    }
59
60    fn commit_raw(&mut self, raw: u64) {
61        self.tape.commit(raw);
62    }
63
64    fn get_error(&mut self) -> Result<(), Self::Error> {
65        Ok(())
66    }
67
68    fn skip_sep(&mut self) -> bool {
69        // Already lexed: there is no separator atom to skip.
70        false
71    }
72}
rustyfi_syntax/stream.rs

rustyfi_syntax/
stream.rs
