From d685e6f1409048fecc8f171f01c873c392923a74 Mon Sep 17 00:00:00 2001
From: Aaron Braunstein <aaron.braunstein@dremio.com>
Date: Thu, 26 Oct 2023 03:22:32 -0700
Subject: [PATCH] Do not explore beyond rule stop states when computing
 possible next tokens during error recovery

Fixes https://github.com/tunnelvisionlabs/antlr4/issues/84
---
 contributors.txt                              |  3 +-
 .../runtime/templates/ParserErrors/Index.stg  |  1 +
 .../templates/ParserErrors/TokenMismatch4.stg | 49 +++++++++++++++++++
 .../org/antlr/v4/runtime/atn/LL1Analyzer.java |  3 ++
 4 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/TokenMismatch4.stg

diff --git a/contributors.txt b/contributors.txt
index e57317c7d0..4acd825016 100644
--- a/contributors.txt
+++ b/contributors.txt
@@ -280,4 +280,5 @@ YYYY/MM/DD, github id, Full name, email
 2020/10/16, adarshbhat, Adarsh Bhat, adarshbhat@users.noreply.github.com
 2020/10/20, adamwojs, Adam Wójs, adam[at]wojs.pl
 2020/10/24, cliid, Jiwu Jang, jiwujang@naver.com
-2020/11/05, MichelHartmann, Michel Hartmann, MichelHartmann@users.noreply.github.com
\ No newline at end of file
+2020/11/05, MichelHartmann, Michel Hartmann, MichelHartmann@users.noreply.github.com
+2023/10/26, br0nstein, Aaron Braunstein, aa(last name)@gmail.com
\ No newline at end of file
diff --git a/runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/Index.stg b/runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/Index.stg
index 88e25c6f75..c7520b016a 100644
--- a/runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/Index.stg
+++ b/runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/Index.stg
@@ -32,5 +32,6 @@ TestTemplates ::= [
 	"NoViableAltAvoidance": [],
 	"TokenMismatch2": [],
 	"TokenMismatch3": [],
+	"TokenMismatch4": [],
 	"ExtraneousInput": []
 ]
diff --git a/runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/TokenMismatch4.stg b/runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/TokenMismatch4.stg
new file mode 100644
index 0000000000..d184d90e7f
--- /dev/null
+++ b/runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/ParserErrors/TokenMismatch4.stg
@@ -0,0 +1,49 @@
+TestType() ::= "Parser"
+
+Options ::= [
+	"Debug": false
+]
+
+Grammar ::= [
+	"T": {<grammar("T")>}
+]
+
+Input() ::= "SELECT CONCAT() FROM tbl"
+
+Rule() ::= "s"
+
+Output() ::= <<
+(selectStatement (selectQuery SELECT (expr (func CONCAT ( (expr )))) (fromClause FROM tbl)) limitOpt)
+Error encountered: [@3,14:14=')',\<7>,1:14]<\n>
+>>
+
+Errors() ::= <<
+line 1:14 mismatched input ')' expecting {IDENTIFIER, NUMBER}<\n>
+>>
+
+grammar(grammarName) ::= <<
+grammar <grammarName>;
+
+<ImportVisitor("T")>
+<ErrorVisitor("T")>
+
+s
+@init {
+<BuildParseTrees()>
+}
+@after {
+<ToStringTree("$r.ctx"):writeln()>
+<WalkVisitor("$ctx")>
+}
+  : r=selectStatement ;
+selectStatement : selectQuery limitOpt ;
+selectQuery : 'SELECT' (expr | '*') fromClause? ;
+limitOpt : ('LIMIT' NUMBER)? ;
+expr : func | IDENTIFIER | NUMBER ;
+fromClause : 'FROM' IDENTIFIER ;
+func : IDENTIFIER '(' expr ',' expr (',' expr)* ')' ;
+parenthesizedSelectQueryOrExpr : '(' (selectQuery limitOpt | expr) ')' ;
+IDENTIFIER : [a-zA-Z]+ ;
+NUMBER : [1-9][0-9]* ;
+WS : [ \r\t\n]+ -> skip ;
+>>
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 b337dfe9bc..2287abc442 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/atn/LL1Analyzer.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/atn/LL1Analyzer.java
@@ -190,6 +190,9 @@ protected void _LOOK(@NotNull ATNState s,
 					calledRuleStack.set(s.ruleIndex);
 				}
 			}
+			if (!PredictionContext.isEmptyLocal(ctx)) {
+				return;
+			}
         }
 
         int n = s.getNumberOfTransitions();