Merge branch 'atnstate-reachability-test' of github.com:sharwell/antlr4

runtime/Java/src/org/antlr/v4/runtime/atn/ATNSimulator.java

@@ -60,6 +60,10 @@ public abstract class ATNSimulator {
 		int p = 0;
 		atn.grammarType = toInt(data[p++]);
 		atn.maxTokenType = toInt(data[p++]);
+
+		//
+		// STATES
+		//
 		int nstates = toInt(data[p++]);
 		for (int i=1; i<=nstates; i++) {
 			int stype = toInt(data[p++]);
@@ -75,6 +79,10 @@ public abstract class ATNSimulator {
 			}
 			atn.addState(s);
 		}
+
+		//
+		// RULES
+		//
 		int nrules = toInt(data[p++]);
 		if ( atn.grammarType == ATN.LEXER ) {
 			atn.ruleToTokenType = new int[nrules];
@@ -92,11 +100,19 @@ public abstract class ATNSimulator {
 				atn.ruleToActionIndex[i] = actionIndex;
 			}
 		}
+
+		//
+		// MODES
+		//
 		int nmodes = toInt(data[p++]);
 		for (int i=0; i<nmodes; i++) {
 			int s = toInt(data[p++]);
 			atn.modeToStartState.add((TokensStartState)atn.states.get(s));
 		}
+
+		//
+		// SETS
+		//
 		int nsets = toInt(data[p++]);
 		for (int i=1; i<=nsets; i++) {
 			int nintervals = toInt(data[p]);
@@ -108,6 +124,10 @@ public abstract class ATNSimulator {
 				p += 2;
 			}
 		}
+
+		//
+		// EDGES
+		//
 		int nedges = toInt(data[p++]);
 		for (int i=1; i<=nedges; i++) {
 			int src = toInt(data[p]);
@@ -125,6 +145,10 @@ public abstract class ATNSimulator {
 			srcState.addTransition(trans);
 			p += 6;
 		}
+
+		//
+		// DECISIONS
+		//
 		int ndecisions = toInt(data[p++]);
 		for (int i=1; i<=ndecisions; i++) {
 			int s = toInt(data[p++]);
@@ -134,6 +158,7 @@ public abstract class ATNSimulator {
 			decState.decision = i-1;
 			decState.isGreedy = isGreedy==1;
 		}
+
 		return atn;
 	}
 

runtime/Java/src/org/antlr/v4/runtime/atn/Transition.java

@@ -91,7 +91,13 @@ public abstract class Transition {
 	@NotNull
 	public ATNState target;
 
-	protected Transition(@NotNull ATNState target) { this.target = target; }
+	protected Transition(@NotNull ATNState target) {
+		if (target == null) {
+			throw new NullPointerException("target cannot be null.");
+		}
+
+		this.target = target;
+	}
 
 	public int getSerializationType() { return 0; }
 

tool/src/org/antlr/v4/automata/ATNSerializer.java

@@ -133,6 +133,11 @@ public class ATNSerializer {
 			if ( s==null ) continue; // might be optimized away
 			for (int i=0; i<s.getNumberOfTransitions(); i++) {
 				Transition t = s.transition(i);
+
+				if (atn.states.get(t.target.stateNumber) == null) {
+					throw new IllegalStateException("Cannot serialize a transition to a removed state.");
+				}
+
 				int src = s.stateNumber;
 				int trg = t.target.stateNumber;
 				int edgeType = Transition.serializationTypes.get(t.getClass());

tool/test/org/antlr/v4/test/TestParseErrors.java

@@ -28,6 +28,7 @@
 
 package org.antlr.v4.test;
 
+import org.antlr.v4.automata.ATNSerializer;
 import org.junit.Test;
 
 /** test runtime parse errors */
@@ -253,4 +254,27 @@ public class TestParseErrors extends BaseTest {
 		assertEquals(expecting, result);
 	}
 
+	/**
+	 * This is a regression test for #45 "NullPointerException in ATNConfig.hashCode".
+	 * https://github.com/antlr/antlr4/issues/45
+	 *
+	 * The original cause of this issue was an error in the tool's ATN state optimization,
+	 * which is now detected early in {@link ATNSerializer} by ensuring that all
+	 * serialized transitions point to states which were not removed.
+	 */
+	@Test
+	public void testInvalidATNStateRemoval() throws Exception {
+		String grammar =
+			"grammar T;\n" +
+			"start : ID ':' expr;\n" +
+			"expr : primary expr? {} | expr '->' ID;\n" +
+			"primary : ID;\n" +
+			"ID : [a-z]+;\n" +
+			"\n";
+		String result = execParser("T.g", grammar, "TParser", "TLexer", "start", "x:x", true);
+		String expecting = "";
+		assertEquals(expecting, result);
+		assertNull(this.stderrDuringParse);
+	}
+
 }