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in lane table mode, run algorithm even with just one reduce

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Otherwise, we get errors in the existing error recovery tests.

cc #240 -- possible fix
This commit is contained in:
Niko Matsakis 2017-08-29 05:46:54 -04:00
parent 920ee76fec
commit 9b7bf48fd8
1 changed files with 19 additions and 2 deletions
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21
lalrpop/src/lr1/lane_table/construct/mod.rs
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@ -114,9 +114,25 @@ impl<'grammar> LaneTableConstruct<'grammar> {
debug!("resolve_inconsistencies(inconsistent_state={:?}/{:#?}",
inconsistent_state, states[inconsistent_state.0]);
let actions = super::conflicting_actions(&states[inconsistent_state.0]);
let mut actions = super::conflicting_actions(&states[inconsistent_state.0]);
if actions.is_empty() {
return Ok(());
// This can mean one of two things: only shifts, or a
// single reduction. We have to be careful about states
// with a single reduction: even though such a state is
// not inconsistent (there is only one possible course of
// action), we still want to run the lane table algorithm,
// because otherwise we get states with "complete"
// lookahead, which messes with error recovery.
//
// In particular, if there is too much lookahead, we will
// reduce even when it is inappropriate to do so.
actions = states[inconsistent_state.0].reductions
.iter()
.map(|&(_, prod)| Action::Reduce(prod))
.collect();
if actions.is_empty() {
return Ok(());
}
}
debug!("resolve_inconsistencies: conflicting_actions={:?}", actions);
@ -168,6 +184,7 @@ impl<'grammar> LaneTableConstruct<'grammar> {
Ok(columns) => {
debug!("attempt_lalr, columns={:#?}", columns);
columns.apply(state, actions);
debug!("attempt_lalr, state={:#?}", state);
true
}
Err(OverlappingLookahead) => {