Properly show defaults for value types in sighelp

src/Features/Core/Portable/ChangeSignature/AbstractChangeSignatureService.cs

@@ -166,11 +166,8 @@ internal ChangeSignatureResult ChangeSignatureWithContext(ChangeSignatureAnalyze
 
         internal ChangeSignatureOptionsResult GetChangeSignatureOptions(ChangeSignatureAnalyzedContext context)
         {
-            var notificationService = context.Solution.Workspace.Services.GetService<INotificationService>();
             var changeSignatureOptionsService = context.Solution.Workspace.Services.GetService<IChangeSignatureOptionsService>();
-
-            var isExtensionMethod = context.Symbol is IMethodSymbol && (context.Symbol as IMethodSymbol).IsExtensionMethod;
-            return changeSignatureOptionsService.GetChangeSignatureOptions(context.Symbol, context.ParameterConfiguration, notificationService);
+            return changeSignatureOptionsService.GetChangeSignatureOptions(context.Symbol, context.ParameterConfiguration);
         }
 
         private static async Task<ImmutableArray<ReferencedSymbol>> FindChangeSignatureReferencesAsync(

src/Features/Core/Portable/ChangeSignature/IChangeSignatureOptionsService.cs

@@ -3,15 +3,11 @@
 // See the LICENSE file in the project root for more information.
 
 using Microsoft.CodeAnalysis.Host;
-using Microsoft.CodeAnalysis.Notification;
 
 namespace Microsoft.CodeAnalysis.ChangeSignature
 {
     internal interface IChangeSignatureOptionsService : IWorkspaceService
     {
-        ChangeSignatureOptionsResult GetChangeSignatureOptions(
-            ISymbol symbol,
-            ParameterConfiguration parameters,
-            INotificationService notificationService);
+        ChangeSignatureOptionsResult GetChangeSignatureOptions(ISymbol symbol, ParameterConfiguration parameters);
     }
 }

src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureDialogViewModel.cs

@@ -20,11 +20,9 @@ namespace Microsoft.VisualStudio.LanguageServices.Implementation.ChangeSignature
 {
     internal class ChangeSignatureDialogViewModel : AbstractNotifyPropertyChanged
     {
-        private readonly INotificationService _notificationService;
         private readonly IClassificationFormatMap _classificationFormatMap;
         private readonly ClassificationTypeMap _classificationTypeMap;
         private readonly ParameterConfiguration _originalParameterConfiguration;
-        private readonly ISymbol _symbol;
 
         private readonly ParameterViewModel _thisParameter;
         private readonly List<ParameterViewModel> _parameterGroup1;
@@ -34,10 +32,9 @@ internal class ChangeSignatureDialogViewModel : AbstractNotifyPropertyChanged
         private ImmutableArray<SymbolDisplayPart> _declarationParts;
         private bool _previewChanges;
 
-        internal ChangeSignatureDialogViewModel(INotificationService notificationService, ParameterConfiguration parameters, ISymbol symbol, IClassificationFormatMap classificationFormatMap, ClassificationTypeMap classificationTypeMap)
+        internal ChangeSignatureDialogViewModel(ParameterConfiguration parameters, ISymbol symbol, IClassificationFormatMap classificationFormatMap, ClassificationTypeMap classificationTypeMap)
         {
             _originalParameterConfiguration = parameters;
-            _notificationService = notificationService;
             _classificationFormatMap = classificationFormatMap;
             _classificationTypeMap = classificationTypeMap;
 
@@ -52,7 +49,6 @@ internal ChangeSignatureDialogViewModel(INotificationService notificationService
                 _paramsParameter = new ParameterViewModel(this, parameters.ParamsParameter);
             }
 
-            _symbol = symbol;
             _declarationParts = symbol.ToDisplayParts(s_symbolDeclarationDisplayFormat);
 
             _parameterGroup1 = parameters.ParametersWithoutDefaultValues.Select(p => new ParameterViewModel(this, p)).ToList();
@@ -509,25 +505,22 @@ public string Default
                 get
                 {
                     if (!ParameterSymbol.HasExplicitDefaultValue)
-                    {
                         return string.Empty;
-                    }
-                    switch (ParameterSymbol.Language)
+
+                    return ParameterSymbol.Language switch
                     {
-                        case LanguageNames.CSharp:
-                            return NullText("null");
-                        case LanguageNames.VisualBasic:
-                            return NullText("Nothing");
-                    }
-                    return string.Empty;
+                        LanguageNames.CSharp => NullText("null", "default"),
+                        LanguageNames.VisualBasic => NullText("Nothing", "Nothing"),
+                        _ => string.Empty,
+                    };
 
-                    string NullText(string @null)
+                    string NullText(string @null, string @default)
                     {
-                        return ParameterSymbol.ExplicitDefaultValue == null ? @null :
-                               ParameterSymbol.ExplicitDefaultValue is string ? "\"" + ParameterSymbol.ExplicitDefaultValue.ToString() + "\"" :
-                               ParameterSymbol.ExplicitDefaultValue.ToString();
+                        var value = ParameterSymbol.ExplicitDefaultValue;
+                        return value == null
+                            ? ParameterSymbol.Type.IsReferenceType ? @null : @default
+                            : value is string ? "\"" + value.ToString() + "\"" : value.ToString();
                     }
-
                 }
             }
 

src/VisualStudio/Core/Def/Implementation/ChangeSignature/VisualStudioChangeSignatureOptionsService.cs

@@ -25,9 +25,9 @@ public VisualStudioChangeSignatureOptionsService(IClassificationFormatMapService
             _classificationTypeMap = classificationTypeMap;
         }
 
-        public ChangeSignatureOptionsResult GetChangeSignatureOptions(ISymbol symbol, ParameterConfiguration parameters, INotificationService notificationService)
+        public ChangeSignatureOptionsResult GetChangeSignatureOptions(ISymbol symbol, ParameterConfiguration parameters)
         {
-            var viewModel = new ChangeSignatureDialogViewModel(notificationService, parameters, symbol, _classificationFormatMap, _classificationTypeMap);
+            var viewModel = new ChangeSignatureDialogViewModel(parameters, symbol, _classificationFormatMap, _classificationTypeMap);
 
             var dialog = new ChangeSignatureDialog(viewModel);
             var result = dialog.ShowModal();