Merge pull request #9268 from Pilchie/Port150343

Dont add IndentOperation for Broken BracketedArgumentList

src/EditorFeatures/CSharp/Formatting/Indentation/CSharpIndentationService.cs

@@ -116,7 +116,9 @@ public override void AddIndentBlockOperations(List<IndentBlockOperation> list, S
                 }
 
                 var argument = node as BaseArgumentListSyntax;
-                if (argument != null && argument.Parent.Kind() != SyntaxKind.ThisConstructorInitializer)
+                if (argument != null &&
+                    argument.Parent.Kind() != SyntaxKind.ThisConstructorInitializer &&
+                    !IsBracketedArgumentListMissingBrackets(argument as BracketedArgumentListSyntax))
                 {
                     AddIndentBlockOperations(list, argument);
                     return;
@@ -153,6 +155,11 @@ public override void AddIndentBlockOperations(List<IndentBlockOperation> list, S
                 }
             }
 
+            private bool IsBracketedArgumentListMissingBrackets(BracketedArgumentListSyntax node)
+            {
+                return node != null && node.OpenBracketToken.IsMissing && node.CloseBracketToken.IsMissing;
+            }
+
             private void ReplaceCaseIndentationRules(List<IndentBlockOperation> list, SyntaxNode node)
             {
                 var section = node as SwitchSectionSyntax;

src/EditorFeatures/CSharpTest/Formatting/Indentation/SmartIndenterTests.cs

@@ -2570,6 +2570,26 @@ class C
                 expectedIndentation: 8);
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.SmartIndent)]
+        public async Task DontCreateIndentOperationForBrokenBracketedArgumentList()
+        {
+            var code = @"
+class Program
+{
+    static void M()
+    {
+        string (userInput == ""Y"")
+
+    }
+}
+";
+
+            await AssertSmartIndentAsync(
+                code,
+                indentationLine: 6,
+                expectedIndentation: 12);
+        }
+
         private static async Task AssertSmartIndentInProjectionAsync(string markup, int expectedIndentation, CSharpParseOptions options = null)
         {
             var optionsSet = options != null