From 61ed3bc01940995031d64768d5ee0b8ef037750c Mon Sep 17 00:00:00 2001
From: Terence Parr <parrt@antlr.org>
Date: Sun, 4 Nov 2012 17:02:41 -0800
Subject: [PATCH] Revert "Simplify Parser.getExpectedTokens and
 DefaultErrorStrategy.getErrorRecoverySet"

This reverts commit d33172dce5cf7f41c00f7c3ed772ce2b927f0a60.
---
 .../v4/runtime/DefaultErrorStrategy.java      | 16 ++++++++++++++--
 .../Java/src/org/antlr/v4/runtime/Parser.java | 19 ++++++++++++++++++-
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java b/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
index 82592ad4d..838fed58f 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
@@ -34,6 +34,7 @@ import org.antlr.v4.runtime.atn.ATNState;
 import org.antlr.v4.runtime.atn.BlockStartState;
 import org.antlr.v4.runtime.atn.PlusBlockStartState;
 import org.antlr.v4.runtime.atn.PlusLoopbackState;
+import org.antlr.v4.runtime.atn.RuleTransition;
 import org.antlr.v4.runtime.atn.StarLoopEntryState;
 import org.antlr.v4.runtime.atn.StarLoopbackState;
 import org.antlr.v4.runtime.misc.IntervalSet;
@@ -521,8 +522,19 @@ public class DefaultErrorStrategy implements ANTLRErrorStrategy {
 	 */
 	protected IntervalSet getErrorRecoverySet(Parser recognizer) {
 		ATN atn = recognizer.getInterpreter().atn;
-		ParserRuleContext ctx = recognizer._ctx;
-		return atn.nextTokens(atn.states.get(ctx.s), ctx);
+		RuleContext ctx = recognizer._ctx;
+		IntervalSet recoverSet = new IntervalSet();
+		while ( ctx!=null && ctx.invokingState>=0 ) {
+			// compute what follows who invoked us
+			ATNState invokingState = atn.states.get(ctx.invokingState);
+			RuleTransition rt = (RuleTransition)invokingState.transition(0);
+			IntervalSet follow = atn.nextTokens(rt.followState);
+			recoverSet.addAll(follow);
+			ctx = ctx.parent;
+		}
+        recoverSet.remove(Token.EPSILON);
+//		System.out.println("recover set "+recoverSet.toString(recognizer.getTokenNames()));
+		return recoverSet;
 	}
 
 	/** Consume tokens until one matches the given token set */
diff --git a/runtime/Java/src/org/antlr/v4/runtime/Parser.java b/runtime/Java/src/org/antlr/v4/runtime/Parser.java
index 0e5059cee..3d5622e1c 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/Parser.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/Parser.java
@@ -547,7 +547,24 @@ public abstract class Parser extends Recognizer<Token, ParserATNSimulator> {
         ATN atn = getInterpreter().atn;
 		ParserRuleContext ctx = _ctx;
         ATNState s = atn.states.get(ctx.s);
-		return atn.nextTokens(s, ctx);
+        IntervalSet following = atn.nextTokens(s);
+//        System.out.println("following "+s+"="+following);
+        if ( !following.contains(Token.EPSILON) ) return following;
+        IntervalSet expected = new IntervalSet();
+        expected.addAll(following);
+        expected.remove(Token.EPSILON);
+        while ( ctx!=null && ctx.invokingState>=0 && following.contains(Token.EPSILON) ) {
+            ATNState invokingState = atn.states.get(ctx.invokingState);
+            RuleTransition rt = (RuleTransition)invokingState.transition(0);
+            following = atn.nextTokens(rt.followState);
+            expected.addAll(following);
+            expected.remove(Token.EPSILON);
+            ctx = (ParserRuleContext)ctx.parent;
+        }
+        if ( following.contains(Token.EPSILON) ) {
+            expected.add(Token.EOF);
+        }
+        return expected;
    	}
 
     public IntervalSet getExpectedTokensWithinCurrentRule() {