MsgPack006 diagnostic error is not properly located on the attribute instead of the intended formatter class

src/MessagePackAnalyzer/TypeCollector.cs

@@ -191,8 +191,9 @@ namespace MessagePackAnalyzer
                 var isMessagePackFormatter = formatterType.AllInterfaces.Any(x => x.Equals(this.typeReferences.MessagePackFormatter));
                 if (!isMessagePackFormatter)
                 {
+                    var location = formatterAttr.ApplicationSyntaxReference.SyntaxTree.GetLocation(formatterAttr.ApplicationSyntaxReference.Span);
                     var typeInfo = ImmutableDictionary.Create<string, string>().Add("type", formatterType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat));
-                    this.ReportContext.Add(Diagnostic.Create(MessagePackAnalyzer.MessageFormatterMustBeMessagePackFormatter, formatterType.Locations[0], typeInfo));
+                    this.ReportContext.Add(Diagnostic.Create(MessagePackAnalyzer.MessageFormatterMustBeMessagePackFormatter, location, typeInfo));
                 }
 
                 return;

tests/MessagePackAnalyzer.Tests/MessagePackAnalyzerTests.cs

@@ -57,9 +57,9 @@ public class SomeClass {
     {
         string input = Preamble + @"using MessagePack.Formatters;
 
-public class {|MsgPack006:InvalidMessageFormatter|} { }
+public class InvalidMessageFormatter { }
 
-[MessagePackFormatter(typeof(InvalidMessageFormatter))]
+[{|MsgPack006:MessagePackFormatter(typeof(InvalidMessageFormatter))|}]
 public struct Foo
 {
 }
@@ -74,7 +74,6 @@ public class SomeClass {
         await VerifyCS.VerifyAnalyzerAsync(input);
     }
 
-
     [Fact]
     public async Task NullStringKey()
     {