From 98ae1a1499db9801bbd73cef338550eea3d52df7 Mon Sep 17 00:00:00 2001
From: Alexander Luzgarev <mahalex@gmail.com>
Date: Thu, 21 Apr 2022 18:12:26 +0200
Subject: [PATCH] Fix infinite loop when parsing parameter list

This fixes a bug reported by David Garrison: on
encountering the new function argument validation
syntax, the parser went into an infinite loop.
---
 Parser.Tests/MParserShould.cs   | 30 ++++++++++++++++++++++++++++++
 Parser/Internal/MParserGreen.cs |  4 ++++
 2 files changed, 34 insertions(+)

diff --git a/Parser.Tests/MParserShould.cs b/Parser.Tests/MParserShould.cs
index 7aa648d..0a47f54 100644
--- a/Parser.Tests/MParserShould.cs
+++ b/Parser.Tests/MParserShould.cs
@@ -1,5 +1,6 @@
 using Xunit;
 using FluentAssertions;
+using System;
 
 namespace Parser.Tests
 {
@@ -150,5 +151,34 @@ namespace Parser.Tests
             rhs.Span.Start.Should().Be(16);
             rhs.Span.End.Should().Be(17);
         }
+
+        [Fact]
+        public void NotHangOnUnknownSyntax()
+        {
+            var text = @"
+classdef myClass
+    properties
+        Channel;
+        NodeID;
+        Node;
+    end
+    methods
+        function this = sendData(this, arg1, arg2)
+            arguments
+                this (1,1) myClass
+                arg1 (1,1) double {mustBeNonnegative}
+                arg2 (1,1) double {mustBeNonnegative}
+            end
+            If (arg1 = 0)
+            this.NodeID = 3;
+        end
+    end
+    function this = getData(this, arg1, arg2)
+    end
+end";
+            var sut = GetSut(text);
+            Func<SyntaxTree> action = sut.Parse;
+            action.Should().Throw<ParsingException>();
+        }
     }
 }
\ No newline at end of file
diff --git a/Parser/Internal/MParserGreen.cs b/Parser/Internal/MParserGreen.cs
index 32851ba..f9d3480 100644
--- a/Parser/Internal/MParserGreen.cs
+++ b/Parser/Internal/MParserGreen.cs
@@ -170,6 +170,10 @@ namespace Parser.Internal
                 {
                     var identifierToken = EatToken(TokenKind.IdentifierToken);
                     builder.Add(Factory.IdentifierNameExpressionSyntax(identifierToken));
+                    if (identifierToken.IsMissing)
+                    {
+                        break;
+                    }
                 }
             }