From 68b9798d6f543b93bb66502e4826b06218170c57 Mon Sep 17 00:00:00 2001
From: Sam Harwell <sam@tunnelvisionlabs.com>
Date: Sun, 4 Nov 2012 13:32:45 -0600
Subject: [PATCH] LL1Analyzer adds EOF to expected tokens set if closure
 reaches end of start rule.

---
 .../org/antlr/v4/runtime/atn/LL1Analyzer.java | 35 ++++++++++++-------
 1 file changed, 23 insertions(+), 12 deletions(-)

diff --git a/runtime/Java/src/org/antlr/v4/runtime/atn/LL1Analyzer.java b/runtime/Java/src/org/antlr/v4/runtime/atn/LL1Analyzer.java
index caa7c4f05..c22cbdd67 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/atn/LL1Analyzer.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/atn/LL1Analyzer.java
@@ -29,6 +29,7 @@
 
 package org.antlr.v4.runtime.atn;
 
+import org.antlr.v4.runtime.IntStream;
 import org.antlr.v4.runtime.RuleContext;
 import org.antlr.v4.runtime.Token;
 import org.antlr.v4.runtime.misc.IntervalSet;
@@ -63,7 +64,7 @@ public class LL1Analyzer {
 			boolean seeThruPreds = false; // fail to get lookahead upon pred
 			_LOOK(s.transition(alt - 1).target,
 				  PredictionContext.EMPTY,
-				  look[alt], lookBusy, seeThruPreds);
+				  look[alt], lookBusy, seeThruPreds, false);
 			// Wipe out lookahead for this alternative if we found nothing
 			// or we had a predicate when we !seeThruPreds
 			if ( look[alt].size()==0 || look[alt].contains(HIT_PRED) ) {
@@ -73,15 +74,21 @@ public class LL1Analyzer {
 		return look;
 	}
 
-    /** Get lookahead, using ctx if we reach end of rule. If ctx is EMPTY, don't chase FOLLOW.
-     *  If ctx is null, EPSILON is in set if we can reach end of rule.
-     */
+	/**
+	 * Get lookahead, using {@code ctx} if we reach end of rule. If {@code ctx}
+	 * is {@code null} or {@link RuleContext#EMPTY EMPTY}, don't chase FOLLOW.
+	 * If {@code ctx} is {@code null}, {@link Token#EPSILON EPSILON} is in set
+	 * if we can reach end of rule. If {@code ctx} is
+	 * {@link RuleContext#EMPTY EMPTY}, {@link IntStream#EOF EOF} is in set if
+	 * we can reach end of rule.
+	 */
     @NotNull
    	public IntervalSet LOOK(@NotNull ATNState s, @Nullable RuleContext ctx) {
    		IntervalSet r = new IntervalSet();
 		boolean seeThruPreds = true; // ignore preds; get all lookahead
-   		_LOOK(s, PredictionContext.fromRuleContext(s.atn, ctx),
-			  r, new HashSet<ATNConfig>(), seeThruPreds);
+		PredictionContext lookContext = ctx != null ? PredictionContext.fromRuleContext(s.atn, ctx) : null;
+   		_LOOK(s, lookContext,
+			  r, new HashSet<ATNConfig>(), seeThruPreds, true);
    		return r;
    	}
 
@@ -95,7 +102,7 @@ public class LL1Analyzer {
     protected void _LOOK(@NotNull ATNState s, @Nullable PredictionContext ctx,
 						 @NotNull IntervalSet look,
                          @NotNull Set<ATNConfig> lookBusy,
-						 boolean seeThruPreds)
+						 boolean seeThruPreds, boolean addEOF)
 	{
 //		System.out.println("_LOOK("+s.stateNumber+", ctx="+ctx);
         ATNConfig c = new ATNConfig(s, 0, ctx);
@@ -105,13 +112,17 @@ public class LL1Analyzer {
             if ( ctx==null ) {
                 look.add(Token.EPSILON);
                 return;
-            }
+            } else if (ctx.isEmpty() && addEOF) {
+				look.add(Token.EOF);
+				return;
+			}
+
 			if ( ctx != PredictionContext.EMPTY ) {
 				// run thru all possible stack tops in ctx
 				for (SingletonPredictionContext p : ctx) {
 					ATNState returnState = atn.states.get(p.returnState);
 //					System.out.println("popping back to "+retState);
-					_LOOK(returnState, p.parent, look, lookBusy, seeThruPreds);
+					_LOOK(returnState, p.parent, look, lookBusy, seeThruPreds, addEOF);
 				}
 				return;
 			}
@@ -123,18 +134,18 @@ public class LL1Analyzer {
 			if ( t.getClass() == RuleTransition.class ) {
 				PredictionContext newContext =
 					SingletonPredictionContext.create(ctx, ((RuleTransition)t).followState.stateNumber);
-				_LOOK(t.target, newContext, look, lookBusy, seeThruPreds);
+				_LOOK(t.target, newContext, look, lookBusy, seeThruPreds, addEOF);
 			}
 			else if ( t instanceof PredicateTransition ) {
 				if ( seeThruPreds ) {
-					_LOOK(t.target, ctx, look, lookBusy, seeThruPreds);
+					_LOOK(t.target, ctx, look, lookBusy, seeThruPreds, addEOF);
 				}
 				else {
 					look.add(HIT_PRED);
 				}
 			}
 			else if ( t.isEpsilon() ) {
-				_LOOK(t.target, ctx, look, lookBusy, seeThruPreds);
+				_LOOK(t.target, ctx, look, lookBusy, seeThruPreds, addEOF);
 			}
 			else if ( t.getClass() == WildcardTransition.class ) {
 				look.addAll( IntervalSet.of(Token.MIN_USER_TOKEN_TYPE, atn.maxTokenType) );