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NFA parser for mbe matcher

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This commit is contained in:
Edwin Cheng 2021-02-02 04:42:37 +08:00
parent 7f57a01b3d
commit cff2201c30
9 changed files with 592 additions and 175 deletions
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16
crates/mbe/src/expander.rs
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@ -5,7 +5,7 @@
mod matcher;
mod transcriber;
use rustc_hash::FxHashMap;
use smallvec::SmallVec;
use syntax::SmolStr;
use crate::{ExpandError, ExpandResult};
@ -28,10 +28,10 @@ pub(crate) fn expand_rules(
return ExpandResult::ok(value);
}
}
// Use the rule if we matched more tokens, or had fewer errors
// Use the rule if we matched more tokens, or bound variables count
if let Some((prev_match, _)) = &match_ {
if (new_match.unmatched_tts, new_match.err_count)
< (prev_match.unmatched_tts, prev_match.err_count)
if (new_match.unmatched_tts, -(new_match.bound_count as i32))
< (prev_match.unmatched_tts, -(prev_match.bound_count as i32))
{
match_ = Some((new_match, rule));
}
@ -94,19 +94,19 @@ pub(crate) fn expand_rules(
/// In other words, `Bindings` is a *multi* mapping from `SmolStr` to
/// `tt::TokenTree`, where the index to select a particular `TokenTree` among
/// many is not a plain `usize`, but an `&[usize]`.
#[derive(Debug, Default)]
#[derive(Debug, Default, Clone, PartialEq, Eq)]
struct Bindings {
inner: FxHashMap<SmolStr, Binding>,
inner: SmallVec<[(SmolStr, Binding); 4]>,
}
#[derive(Debug)]
#[derive(Debug, Clone, PartialEq, Eq)]
enum Binding {
Fragment(Fragment),
Nested(Vec<Binding>),
Empty,
}
#[derive(Debug, Clone)]
#[derive(Debug, Clone, PartialEq, Eq)]
enum Fragment {
/// token fragments are just copy-pasted into the output
Tokens(tt::TokenTree),