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Add error 146: non-fragment lexer rule can match the empty string

This commit is contained in:
Sam Harwell 2013-01-14 18:02:17 -06:00
parent 9edec91022
commit 3521a00dbb
3 changed files with 43 additions and 3 deletions
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27
tool/src/org/antlr/v4/analysis/AnalysisPipeline.java
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@ -31,10 +31,14 @@
package org.antlr.v4.analysis;
import org.antlr.v4.misc.Utils;
import org.antlr.v4.runtime.Token;
import org.antlr.v4.runtime.atn.DecisionState;
import org.antlr.v4.runtime.atn.LL1Analyzer;
import org.antlr.v4.runtime.misc.IntervalSet;
import org.antlr.v4.tool.ErrorType;
import org.antlr.v4.tool.Grammar;
import org.antlr.v4.tool.Rule;
import org.antlr.v4.tool.ast.GrammarAST;
import java.util.ArrayList;
import java.util.Arrays;
@ -52,11 +56,30 @@ public class AnalysisPipeline {
lr.check();
if ( !lr.listOfRecursiveCycles.isEmpty() ) return; // bail out
if (g.isLexer()) {
processLexer();
} else {
// BUILD DFA FOR EACH DECISION
if ( !g.isLexer() ) processParser();
processParser();
}
}
void processParser() {
protected void processLexer() {
// make sure all non-fragment lexer rules must match at least one symbol
for (Rule rule : g.rules.values()) {
if (rule.isFragment()) {
continue;
}
LL1Analyzer analyzer = new LL1Analyzer(g.atn);
IntervalSet look = analyzer.LOOK(g.atn.ruleToStartState[rule.index], null);
if (look.contains(Token.EPSILON)) {
g.tool.errMgr.grammarError(ErrorType.EPSILON_TOKEN, g.fileName, ((GrammarAST)rule.ast.getChild(0)).getToken(), rule.name);
}
}
}
protected void processParser() {
g.decisionLOOK = new ArrayList<IntervalSet[]>(g.atn.getNumberOfDecisions()+1);
for (DecisionState s : g.atn.decisionToState) {
g.tool.log("LL1", "\nDECISION "+s.decision+" in rule "+g.getRule(s.ruleIndex).name);

1
tool/src/org/antlr/v4/tool/ErrorType.java
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@ -128,6 +128,7 @@ public enum ErrorType {
LOCAL_CONFLICTS_WITH_RETVAL(143, "local '<arg>' conflicts with return value with same name", ErrorSeverity.ERROR),
INVALID_LITERAL_IN_LEXER_SET(144, "multi-character literals are not allowed in lexer sets: <arg>", ErrorSeverity.ERROR),
MODE_WITHOUT_RULES(145, "lexer mode '<arg>' must contain at least one non-fragment rule", ErrorSeverity.ERROR),
EPSILON_TOKEN(146, "non-fragment lexer rule '<arg>' can match the empty string", ErrorSeverity.ERROR),
// Backward incompatibility errors
V3_TREE_GRAMMAR(200, "tree grammars are not supported in ANTLR 4", ErrorSeverity.ERROR),

16
tool/test/org/antlr/v4/test/TestSymbolIssues.java
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@ -152,4 +152,20 @@ public class TestSymbolIssues extends BaseTest {
testErrors(test, false);
}
@Test public void testEmptyLexerRuleDetection() throws Exception {
String[] test = {
"lexer grammar L;\n" +
"A : 'a';\n" +
"WS : [ \t]* -> skip;\n" +
"mode X;\n" +
" B : C;\n" +
" fragment C : A | (A C)?;",
"error(" + ErrorType.EPSILON_TOKEN.code + "): L.g4:3:0: non-fragment lexer rule 'WS' can match the empty string\n" +
"error(" + ErrorType.EPSILON_TOKEN.code + "): L.g4:5:2: non-fragment lexer rule 'B' can match the empty string\n"
};
testErrors(test, false);
}
}