Merge pull request #3179 from vweijsters/fix-3160

Workaround for issue #3160

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers/Helpers/DictionaryExtensions.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+namespace StyleCop.Analyzers.Helpers
+{
+    using System.Collections.Generic;
+
+    internal static class DictionaryExtensions
+    {
+        public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue)
+          where TKey : notnull
+        {
+            if (!dictionary.TryGetValue(key, out var value))
+            {
+                value = defaultValue;
+            }
+
+            return value;
+        }
+    }
+}

StyleCop.Analyzers/StyleCop.Analyzers/OrderingRules/SA1201ElementsMustAppearInTheCorrectOrder.cs

@@ -296,7 +296,11 @@ private static void HandleMemberList(SyntaxNodeAnalysisContext context, Immutabl
 
                 if (index > nextIndex)
                 {
-                    context.ReportDiagnostic(Diagnostic.Create(Descriptor, NamedTypeHelpers.GetNameOrIdentifierLocation(members[i + 1]), MemberNames[nextElementSyntaxKind], MemberNames[elementSyntaxKind]));
+                    // [Issue #3160] Added hardening here to make sure that this won't crash when working with invalid code.
+                    var nextElementMemberName = MemberNames.GetValueOrDefault(nextElementSyntaxKind, "<unknown>");
+                    var elementMemberName = MemberNames.GetValueOrDefault(elementSyntaxKind, "<unknown>");
+
+                    context.ReportDiagnostic(Diagnostic.Create(Descriptor, NamedTypeHelpers.GetNameOrIdentifierLocation(members[i + 1]), nextElementMemberName, elementMemberName));
                 }
             }
         }