Add type hints for collection expressions

src/EditorFeatures/Core/InlineHints/InlineHintsDataTaggerProvider.cs

@@ -70,7 +70,8 @@ protected override ITaggerEventSource CreateEventSource(ITextView textView, ITex
                 option.Equals(InlineHintsOptionsStorage.EnabledForTypes) ||
                 option.Equals(InlineHintsOptionsStorage.ForImplicitVariableTypes) ||
                 option.Equals(InlineHintsOptionsStorage.ForLambdaParameterTypes) ||
-                option.Equals(InlineHintsOptionsStorage.ForImplicitObjectCreation)));
+                option.Equals(InlineHintsOptionsStorage.ForImplicitObjectCreation) ||
+                option.Equals(InlineHintsOptionsStorage.ForCollectionExpressions)));
     }
 
     protected override void AddSpansToTag(ITextView? textView, ITextBuffer subjectBuffer, ref TemporaryArray<SnapshotSpan> result)

src/Features/CSharp/Portable/InlineHints/CSharpInlineTypeHintsService.cs

@@ -30,6 +30,7 @@ public CSharpInlineTypeHintsService()
         bool forImplicitVariableTypes,
         bool forLambdaParameterTypes,
         bool forImplicitObjectCreation,
+        bool forCollectionExpressions,
         CancellationToken cancellationToken)
     {
         if (forImplicitVariableTypes || displayAllOverride)
@@ -101,6 +102,19 @@ public CSharpInlineTypeHintsService()
             }
         }
 
+        if (forCollectionExpressions || displayAllOverride)
+        {
+            if (node is CollectionExpressionSyntax collectionExpression)
+            {
+                var type = semanticModel.GetTypeInfo(collectionExpression, cancellationToken).ConvertedType;
+                if (IsValidType(type))
+                {
+                    var span = new TextSpan(collectionExpression.OpenBracketToken.SpanStart, 0);
+                    return new(type, span, new TextChange(span, type.ToDisplayString(s_minimalTypeStyle)), leadingSpace: true);
+                }
+            }
+        }
+
         return null;
     }
 

src/Features/Core/Portable/InlineHints/AbstractInlineTypeHintsService.cs

@@ -25,6 +25,7 @@ internal abstract class AbstractInlineTypeHintsService : IInlineTypeHintsService
         bool forImplicitVariableTypes,
         bool forLambdaParameterTypes,
         bool forImplicitObjectCreation,
+        bool forCollectionExpressions,
         CancellationToken cancellationToken);
 
     public async Task<ImmutableArray<InlineHint>> GetInlineHintsAsync(
@@ -42,7 +43,8 @@ public async Task<ImmutableArray<InlineHint>> GetInlineHintsAsync(
         var forImplicitVariableTypes = enabledForTypes && options.ForImplicitVariableTypes;
         var forLambdaParameterTypes = enabledForTypes && options.ForLambdaParameterTypes;
         var forImplicitObjectCreation = enabledForTypes && options.ForImplicitObjectCreation;
-        if (!forImplicitVariableTypes && !forLambdaParameterTypes && !forImplicitObjectCreation && !displayAllOverride)
+        var forCollectionExpressions = enabledForTypes && options.ForCollectionExpressions;
+        if (!forImplicitVariableTypes && !forLambdaParameterTypes && !forImplicitObjectCreation && !forCollectionExpressions && !displayAllOverride)
             return [];
 
         var anonymousTypeService = document.GetRequiredLanguageService<IStructuralTypeDisplayService>();
@@ -59,6 +61,7 @@ public async Task<ImmutableArray<InlineHint>> GetInlineHintsAsync(
                 forImplicitVariableTypes,
                 forLambdaParameterTypes,
                 forImplicitObjectCreation,
+                forCollectionExpressions,
                 cancellationToken);
             if (hintOpt == null)
                 continue;

src/Features/Core/Portable/InlineHints/InlineTypeHintsOptions.cs

@@ -13,6 +13,7 @@ internal readonly record struct InlineTypeHintsOptions
     [DataMember] public bool ForImplicitVariableTypes { get; init; } = true;
     [DataMember] public bool ForLambdaParameterTypes { get; init; } = true;
     [DataMember] public bool ForImplicitObjectCreation { get; init; } = true;
+    [DataMember] public bool ForCollectionExpressions { get; init; } = true;
 
     public InlineTypeHintsOptions()
     {

src/LanguageServer/Protocol/Features/Options/InlineHintsOptionsStorage.cs

@@ -37,6 +37,7 @@ public static InlineTypeHintsOptions GetInlineTypeHintsOptions(this IGlobalOptio
                 ForImplicitVariableTypes = globalOptions.GetOption(ForImplicitVariableTypes, language),
                 ForLambdaParameterTypes = globalOptions.GetOption(ForLambdaParameterTypes, language),
                 ForImplicitObjectCreation = globalOptions.GetOption(ForImplicitObjectCreation, language),
+                ForCollectionExpressions = globalOptions.GetOption(ForCollectionExpressions, language),
             };
 
         // Note: inlay hints is the term used in LSP, we Want to use the LSP name when communicate with the LSP client.
@@ -105,5 +106,10 @@ public static InlineTypeHintsOptions GetInlineTypeHintsOptions(this IGlobalOptio
             new("csharp_enable_inlay_hints_for_implicit_object_creation",
                 defaultValue: InlineTypeHintsOptions.Default.ForImplicitObjectCreation,
                 group: s_inlayHintOptionGroup);
+
+        public static readonly PerLanguageOption2<bool> ForCollectionExpressions =
+            new("csharp_enable_inlay_hints_for_collection_expressions",
+                defaultValue: InlineTypeHintsOptions.Default.ForCollectionExpressions,
+                group: s_inlayHintOptionGroup);
     }
 }

src/LanguageServer/Protocol/Handler/Configuration/DidChangeConfigurationNotificationHandler_OptionList.cs

@@ -43,6 +43,7 @@ internal partial class DidChangeConfigurationNotificationHandler
             InlineHintsOptionsStorage.ForImplicitVariableTypes,
             InlineHintsOptionsStorage.ForLambdaParameterTypes,
             InlineHintsOptionsStorage.ForImplicitObjectCreation,
+            InlineHintsOptionsStorage.ForCollectionExpressions,
             FormattingOptions2.TabSize,
             FormattingOptions2.IndentationSize,
             FormattingOptions2.UseTabs,

src/LanguageServer/Protocol/Handler/InlayHint/InlayHintRefreshQueue.cs

@@ -45,7 +45,8 @@ private void OnOptionChanged(object? sender, OptionChangedEventArgs e)
                     option.Equals(InlineHintsOptionsStorage.EnabledForTypes) ||
                     option.Equals(InlineHintsOptionsStorage.ForImplicitVariableTypes) ||
                     option.Equals(InlineHintsOptionsStorage.ForLambdaParameterTypes) ||
-                    option.Equals(InlineHintsOptionsStorage.ForImplicitObjectCreation)))
+                    option.Equals(InlineHintsOptionsStorage.ForImplicitObjectCreation) ||
+                    option.Equals(InlineHintsOptionsStorage.ForCollectionExpressions)))
             {
                 EnqueueRefreshNotification(documentUri: null);
             }

src/LanguageServer/ProtocolUnitTests/Configuration/DidChangeConfigurationNotificationHandlerTest.cs

@@ -133,6 +133,7 @@ public void VerifyLspClientOptionNames()
                 "inlay_hints.csharp_enable_inlay_hints_for_implicit_variable_types",
                 "inlay_hints.csharp_enable_inlay_hints_for_lambda_parameter_types",
                 "inlay_hints.csharp_enable_inlay_hints_for_implicit_object_creation",
+                "inlay_hints.csharp_enable_inlay_hints_for_collection_expressions",
                 "code_style.formatting.indentation_and_spacing.tab_width",
                 "code_style.formatting.indentation_and_spacing.indent_size",
                 "code_style.formatting.indentation_and_spacing.indent_style",

src/VisualStudio/CSharp/Impl/Options/AdvancedOptionPageControl.xaml

@@ -375,6 +375,9 @@
                         <CheckBox x:Uid="ShowHintsForImplicitObjectCreation"
                                   x:Name="ShowHintsForImplicitObjectCreation"
                                   Content="{x:Static local:AdvancedOptionPageStrings.Option_Show_hints_for_implicit_object_creation}" />
+                        <CheckBox x:Uid="ShowHintsForCollectionExpressions"
+                                  x:Name="ShowHintsForCollectionExpressions"
+                                  Content="{x:Static local:AdvancedOptionPageStrings.Option_Show_hints_for_collection_expressions}" />
                     </StackPanel>
                 </StackPanel>
             </GroupBox>

src/VisualStudio/CSharp/Impl/Options/AdvancedOptionPageControl.xaml.cs

@@ -192,6 +192,7 @@ public AdvancedOptionPageControl(OptionStore optionStore, IComponentModel compon
             BindToOption(ShowHintsForVariablesWithInferredTypes, InlineHintsOptionsStorage.ForImplicitVariableTypes, LanguageNames.CSharp);
             BindToOption(ShowHintsForLambdaParameterTypes, InlineHintsOptionsStorage.ForLambdaParameterTypes, LanguageNames.CSharp);
             BindToOption(ShowHintsForImplicitObjectCreation, InlineHintsOptionsStorage.ForImplicitObjectCreation, LanguageNames.CSharp);
+            BindToOption(ShowHintsForCollectionExpressions, InlineHintsOptionsStorage.ForCollectionExpressions, LanguageNames.CSharp);
 
             // Inheritance Margin
             // Leave the null converter here to make sure if the option value is get from the storage (if it is null), the feature will be enabled
@@ -244,6 +245,7 @@ private void UpdateInlineHintsOptions()
             ShowHintsForVariablesWithInferredTypes.IsEnabled = enabledForTypes;
             ShowHintsForLambdaParameterTypes.IsEnabled = enabledForTypes;
             ShowHintsForImplicitObjectCreation.IsEnabled = enabledForTypes;
+            ShowHintsForCollectionExpressions.IsEnabled = enabledForTypes;
         }
 
         private void DisplayInlineParameterNameHints_Checked(object sender, RoutedEventArgs e)

src/VisualStudio/CSharp/Impl/Options/AdvancedOptionPageStrings.cs

@@ -126,6 +126,9 @@ public static string Option_Show_hints_for_lambda_parameter_types
         public static string Option_Show_hints_for_implicit_object_creation
             => ServicesVSResources.Show_hints_for_implicit_object_creation;
 
+        public static string Option_Show_hints_for_collection_expressions
+            => ServicesVSResources.Show_hints_for_collection_expressions;
+
         public static string Option_Display_diagnostics_inline_experimental
             => ServicesVSResources.Display_diagnostics_inline_experimental;
 

src/VisualStudio/Core/Def/Options/VisualStudioOptionStorage.cs

@@ -330,6 +330,7 @@ public bool TryFetch(LocalUserRegistryOptionPersister persister, OptionKey2 opti
         {"dotnet_enable_inlay_hints_for_parameters", new RoamingProfileStorage("TextEditor.%LANGUAGE%.Specific.InlineParameterNameHints")},
         {"csharp_enable_inlay_hints_for_types", new RoamingProfileStorage("TextEditor.%LANGUAGE%.Specific.InlineTypeHints")},
         {"csharp_enable_inlay_hints_for_implicit_object_creation", new RoamingProfileStorage("TextEditor.%LANGUAGE%.Specific.InlineTypeHints.ForImplicitObjectCreation")},
+        {"csharp_enable_inlay_hints_for_collection_expressions", new RoamingProfileStorage("TextEditor.%LANGUAGE%.Specific.InlineTypeHints.ForCollectionExpressions")},
         {"csharp_enable_inlay_hints_for_implicit_variable_types", new RoamingProfileStorage("TextEditor.%LANGUAGE%.Specific.InlineTypeHints.ForImplicitVariableTypes")},
         {"dotnet_enable_inlay_hints_for_indexer_parameters", new RoamingProfileStorage("TextEditor.%LANGUAGE%.Specific.InlineParameterNameHints.ForArrayIndexers")},
         {"csharp_enable_inlay_hints_for_lambda_parameter_types", new RoamingProfileStorage("TextEditor.%LANGUAGE%.Specific.InlineTypeHints.ForLambdaParameterTypes")},

src/VisualStudio/Core/Def/ServicesVSResources.resx

@@ -1936,4 +1936,7 @@ Additional information: {1}</value>
   <data name="Prefer_static_anonymous_functions" xml:space="preserve">
     <value>Prefer static anonymous functions</value>
   </data>
+  <data name="Show_hints_for_collection_expressions" xml:space="preserve">
+    <value>Show hints for collection expressions</value>
+  </data>
 </root>