fix LL1 analyzer

runtime/Java/src/org/antlr/v4/runtime/atn/LL1Analyzer.java

@@ -150,7 +150,8 @@ public class LL1Analyzer {
 			if (ctx == null) {
 				look.add(Token.EPSILON);
 				return;
-			} else if (ctx.isEmpty() && addEOF) {
+			}
+			else if (ctx.isEmpty() && addEOF) {
 				look.add(Token.EOF);
 				return;
 			}
@@ -160,26 +161,26 @@ public class LL1Analyzer {
             if ( ctx==null ) {
                 look.add(Token.EPSILON);
                 return;
-            } else if (ctx.isEmpty() && addEOF) {
+            }
+            else if (ctx.isEmpty() && addEOF) {
 				look.add(Token.EOF);
 				return;
 			}
 
 			if ( ctx != PredictionContext.EMPTY ) {
 				// run thru all possible stack tops in ctx
-				for (int i = 0; i < ctx.size(); i++) {
-					ATNState returnState = atn.states.get(ctx.getReturnState(i));
-//					System.out.println("popping back to "+retState);
-
-					boolean removed = calledRuleStack.get(returnState.ruleIndex);
-					try {
-						calledRuleStack.clear(returnState.ruleIndex);
+				boolean removed = calledRuleStack.get(s.ruleIndex);
+				try {
+					calledRuleStack.clear(s.ruleIndex);
+					for (int i = 0; i < ctx.size(); i++) {
+						ATNState returnState = atn.states.get(ctx.getReturnState(i));
+//					    System.out.println("popping back to "+retState);
 						_LOOK(returnState, stopState, ctx.getParent(i), look, lookBusy, calledRuleStack, seeThruPreds, addEOF);
 					}
-					finally {
-						if (removed) {
-							calledRuleStack.set(returnState.ruleIndex);
-						}
+				}
+				finally {
+					if (removed) {
+						calledRuleStack.set(s.ruleIndex);
 					}
 				}
 				return;

tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java

@@ -317,6 +317,40 @@ public class TestToolSyntaxErrors extends BaseJavaToolTest {
 		super.testErrors(pair, true);
 	}
 
+	// Test for https://github.com/antlr/antlr4/issues/1203
+	@Test public void testEpsilonNestedClosureAnalysis() {
+		String grammar =
+			"grammar T;\n"+
+			"s : (a a)* ;\n"+
+			"a : 'foo'* ;\n";
+		String expected =
+			"error(" + ErrorType.EPSILON_CLOSURE.code + "): T.g4:2:0: rule s contains a closure with at least one alternative that can match an empty string\n";
+
+		String[] pair = new String[] {
+			grammar,
+			expected
+		};
+
+		super.testErrors(pair, true);
+	}
+
+	// Test for https://github.com/antlr/antlr4/issues/1203
+	@Test public void testEpsilonOptionalAndClosureAnalysis() {
+		String grammar =
+			"grammar T;\n"+
+			"s : (a a)? ;\n"+
+			"a : 'foo'* ;\n";
+		String expected =
+			"warning(" + ErrorType.EPSILON_OPTIONAL.code + "): T.g4:2:0: rule s contains an optional block with at least one alternative that can match an empty string\n";
+
+		String[] pair = new String[] {
+			grammar,
+			expected
+		};
+
+		super.testErrors(pair, true);
+	}
+
 	@Test public void testEpsilonOptionalAnalysis() {
 		String grammar =
 			"grammar A;\n"

tool/src/org/antlr/v4/analysis/AnalysisPipeline.java

@@ -34,7 +34,8 @@ public class AnalysisPipeline {
 
 		if (g.isLexer()) {
 			processLexer();
-		} else {
+		}
+		else {
 			// BUILD DFA FOR EACH DECISION
 			processParser();
 		}

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

@@ -113,7 +113,10 @@ public class ParserATNFactory implements ATNFactory {
 
 		for (Triple<Rule, ATNState, ATNState> pair : preventEpsilonClosureBlocks) {
 			LL1Analyzer analyzer = new LL1Analyzer(atn);
-			if (analyzer.LOOK(pair.b, pair.c, null).contains(org.antlr.v4.runtime.Token.EPSILON)) {
+			ATNState blkStart = pair.b;
+			ATNState blkStop = pair.c;
+			IntervalSet lookahead = analyzer.LOOK(blkStart, blkStop, null);
+			if ( lookahead.contains(org.antlr.v4.runtime.Token.EPSILON)) {
 				ErrorType errorType = pair.a instanceof LeftRecursiveRule ? ErrorType.EPSILON_LR_FOLLOW : ErrorType.EPSILON_CLOSURE;
 				g.tool.errMgr.grammarError(errorType, g.fileName, ((GrammarAST)pair.a.ast.getChild(0)).getToken(), pair.a.name);
 			}