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Correctness for lexer DFA with semantic predicate evaluation only requires suppressing single edges from the DFA

This commit is contained in:
Sam Harwell 2012-10-29 11:26:37 -05:00
parent a115490d5e
commit 9873230f55
2 changed files with 15 additions and 15 deletions
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7
runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNConfig.java
View File

@ -63,13 +63,6 @@ public class LexerATNConfig extends ATNConfig {
this.passedThroughNonGreedyDecision = checkNonGreedyDecision(c, state);
}
public LexerATNConfig(@NotNull LexerATNConfig c, @NotNull ATNState state,
@NotNull SemanticContext semanticContext) {
super(c, state, c.context, semanticContext);
this.lexerActionIndex = c.lexerActionIndex;
this.passedThroughNonGreedyDecision = checkNonGreedyDecision(c, state);
}
public LexerATNConfig(@NotNull LexerATNConfig c, @NotNull ATNState state,
int actionIndex)
{

23
runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
View File

@ -585,10 +585,6 @@ public class LexerATNSimulator extends ATNSimulator {
break;
case Transition.PREDICATE:
// if (recog == null) {
// System.out.format("Predicates cannot be evaluated without a recognizer; assuming true.\n");
// }
/* Track traversing semantic predicates. If we traverse,
we cannot add a DFA state for this "reach" computation
because the DFA would not test the predicate again in the
@ -613,7 +609,7 @@ public class LexerATNSimulator extends ATNSimulator {
}
configs.hasSemanticContext = true;
if ( recog == null || recog.sempred(null, pt.ruleIndex, pt.predIndex) ) {
c = new LexerATNConfig(config, t.target, pt.getPredicate());
c = new LexerATNConfig(config, t.target);
}
break;
// ignore actions; just exec one per rule upon accept
@ -676,6 +672,15 @@ public class LexerATNSimulator extends ATNSimulator {
int t,
@NotNull ATNConfigSet q)
{
/* leading to this call, ATNConfigSet.hasSemanticContext is used as a
* marker indicating dynamic predicate evaluation makes this edge
* dependent on the specific input sequence, so the static edge in the
* DFA should be omitted. The target DFAState is still created since
* execATN has the ability to resynchronize with the DFA state cache
* following the predicate evaluation step.
*/
boolean suppressEdge = q.hasSemanticContext;
q.hasSemanticContext = false;
DFAState to = addDFAState(q);
// even if we can add the states, we can't add an edge for labels out of range
@ -683,7 +688,7 @@ public class LexerATNSimulator extends ATNSimulator {
return to;
}
if (from == null || to == null) {
if (from == null || to == null || suppressEdge) {
return to;
}
@ -712,8 +717,10 @@ public class LexerATNSimulator extends ATNSimulator {
*/
@Nullable
protected DFAState addDFAState(@NotNull ATNConfigSet configs) {
// If we eval'd a predicate while filling configs, mustn't create DFA state
if ( configs.hasSemanticContext ) return null;
/* the lexer evaluates predicates on-the-fly; by this point configs
* should not contain any configurations with unevaluated predicates.
*/
assert !configs.hasSemanticContext;
DFAState proposed = new DFAState(configs);
ATNConfig firstConfigWithRuleStopState = null;