Fix bounds in on header attr #37837

src/EditorFeatures/CSharpTest/RefactoringHelpers/RefactoringHelpersTests.cs

@@ -527,6 +527,23 @@ public class Class1
             await TestMissingAsync<MethodDeclarationSyntax>(testText);
         }
 
+        [Fact]
+        [WorkItem(37837, "https://github.com/dotnet/roslyn/issues/37837")]
+        public async Task TestEmptyParameter()
+        {
+            var testText = @"
+using System;
+public class TestAttribute : Attribute { }
+public class Class1
+{
+    static void foo({|result:[Test][||]
+|}    {
+
+    }
+}";
+            await TestAsync<ParameterSyntax>(testText);
+        }
+
         [Fact]
         [WorkItem(37584, "https://github.com/dotnet/roslyn/issues/37584")]
         public async Task TestMissingEmptyMember2()

src/Features/Core/Portable/CodeRefactorings/AbstractRefactoringHelpersService.cs

@@ -473,10 +473,7 @@ private static TextSpan GetSpanWithoutAttributes(SyntaxNode node, SyntaxNode roo
                 var afterAttributesToken = root.FindTokenOnRightOfPosition(endOfAttributeLists);
 
                 var endOfNode = node.Span.End;
-                var startOfTokenAfterAttributes = afterAttributesToken.Span.Start;
-                var startOfNodeWithoutAttributes = endOfNode >= startOfTokenAfterAttributes
-                    ? afterAttributesToken.Span.Start
-                    : endOfNode;
+                var startOfNodeWithoutAttributes = Math.Min(afterAttributesToken.Span.Start, endOfNode);
 
                 return TextSpan.FromBounds(startOfNodeWithoutAttributes, endOfNode);
             }

src/Workspaces/Core/Portable/LanguageServices/SyntaxFactsService/AbstractSyntaxFactsService.cs

@@ -542,11 +542,16 @@ protected TNode TryGetAncestorForLocation<TNode>(int position, SyntaxNode root)
 
         protected int GetStartOfNodeExcludingAttributes(SyntaxNode node)
         {
-            var attributeLists = GetAttributeLists(node);
-            var start = attributeLists.LastOrDefault()?.GetLastToken().GetNextToken().SpanStart ??
-                        node.SpanStart;
+            var attributeList = GetAttributeLists(node);
+            if (attributeList.Any())
+            {
+                var endOfAttributeLists = attributeList.Last().Span.End;
+                var afterAttributesToken = node.FindTokenOnRightOfPosition(endOfAttributeLists);
+
+                return Math.Min(afterAttributesToken.Span.Start, node.Span.End);
+            }
 
-            return start;
+            return node.SpanStart;
         }
 
         public abstract SyntaxList<SyntaxNode> GetAttributeLists(SyntaxNode node);