Introduce local variable supporting target-type new syntax (#76342)

Author: CyrusNajmabadi

src/Features/CSharp/Portable/IntroduceVariable/CSharpIntroduceVariableService_IntroduceLocal.cs

@@ -9,10 +9,12 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeCleanup;
+using Microsoft.CodeAnalysis.CSharp.CodeStyle.TypeStyle;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
+using Microsoft.CodeAnalysis.CSharp.Simplification;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Editing;
 using Microsoft.CodeAnalysis.Formatting;
@@ -28,6 +30,7 @@ internal sealed partial class CSharpIntroduceVariableService
 {
     protected override Document IntroduceLocal(
         SemanticDocument document,
+        CodeCleanupOptions options,
         ExpressionSyntax expression,
         bool allOccurrences,
         bool isConstant,
@@ -47,14 +50,25 @@ protected override Document IntroduceLocal(
             ? TokenList(ConstKeyword)
             : default;
 
+        var updatedExpression = expression.WithoutTrivia();
+        var simplifierOptions = (CSharpSimplifierOptions)options.SimplifierOptions;
+
+        // If the target-type new syntax is preferred and "var" is not preferred under any circumstance, then we use the target-type new syntax.
+        // The approach is not exhaustive. We aim to support codebases that rely strictly on the target-type new syntax (i.e., no "var").
+        if (simplifierOptions.ImplicitObjectCreationWhenTypeIsApparent.Value && simplifierOptions.GetUseVarPreference() == UseVarPreference.None
+            && updatedExpression is ObjectCreationExpressionSyntax objectCreationExpression)
+        {
+            updatedExpression = ImplicitObjectCreationExpression(objectCreationExpression.ArgumentList, objectCreationExpression.Initializer);
+        }
+
         var declarationStatement = LocalDeclarationStatement(
             modifiers,
             VariableDeclaration(
                 GetTypeSyntax(document, expression, cancellationToken),
                 [VariableDeclarator(
                     newLocalNameToken.WithAdditionalAnnotations(RenameAnnotation.Create()),
                     argumentList: null,
-                    EqualsValueClause(expression.WithoutTrivia()))]));
+                    EqualsValueClause(updatedExpression))]));
 
         switch (containerToGenerateInto)
         {

src/Features/CSharpTest/IntroduceVariable/IntroduceVariableTests.cs

@@ -935,13 +935,63 @@ class Program
             {
                 static void Main()
                 {
-                    G<int>.@class {|Rename:@class|} = new G<int>.@class();
+                    G<int>.@class {|Rename:@class|} = new();
                     G<int>.Add(@class);
                 }
             }
             """);
     }
 
+    [Fact]
+    public async Task TestNameVerbatimIdentifier1NoVar_1()
+    {
+        await TestInRegularAndScriptAsync(
+            """
+            static class G<T>
+            {
+                public class @class
+                {
+                }
+
+                public static void Add(object @class)
+                {
+                }
+            }
+
+            class Program
+            {
+                static void Main()
+                {
+                    G<int>.Add([|new G<int>.@class()|]);
+                }
+            }
+            """,
+            """
+            static class G<T>
+            {
+                public class @class
+                {
+                }
+
+                public static void Add(object @class)
+                {
+                }
+            }
+
+            class Program
+            {
+                static void Main()
+                {
+                    G<int>.@class {|Rename:@class|} = new G<int>.@class();
+                    G<int>.Add(@class);
+                }
+            }
+            """, options: new(GetLanguage())
+            {
+                { CSharpCodeStyleOptions.ImplicitObjectCreationWhenTypeIsApparent, CodeStyleOption2.FalseWithSilentEnforcement }
+            });
+    }
+
     [Fact]
     public async Task TestNameVerbatimIdentifier2()
     {
@@ -1018,7 +1068,7 @@ public static void Add(object @class)
 
                 static void Main()
                 {
-                    G<int>.@class {|Rename:@class|} = new G<int>.@class();
+                    G<int>.@class {|Rename:@class|} = new();
                     G<int>.Add(@class);
                 }
             }
@@ -3001,7 +3051,7 @@ class Program
             {
                 static void Main()
                 {
-                    Nullable<int*> {|Rename:v|} = new Nullable<int*>();
+                    Nullable<int*> {|Rename:v|} = new();
                     v.GetValueOrDefault();
                 }
             }
@@ -4283,6 +4333,56 @@ public T this[int i]
         await TestInRegularAndScriptAsync(code, expected, options: ImplicitTypingEverywhere());
     }
 
+    [Fact]
+    public async Task TestIntroduceLocalWithTargetTypedNew()
+    {
+        var code =
+            """
+            using System;
+            class SampleType
+            {
+                public SampleType() 
+                {
+                    int sum = Sum([|new Numbers()|]);
+                }
+
+                private int Sum(Numbers numbers) 
+                {
+                    return 42;
+                }
+
+                private class Numbers {}
+            }
+            """;
+
+        var expected =
+            """
+            using System;
+            class SampleType
+            {
+                public SampleType() 
+                {
+                    Numbers {|Rename:numbers|} = new();
+                    int sum = Sum(numbers);
+                }
+
+                private int Sum(Numbers numbers) 
+                {
+                    return 42;
+                }
+
+                private class Numbers {}
+            }
+            """;
+
+        OptionsCollection optionsCollection = new(GetLanguage())
+        {
+            { CSharpCodeStyleOptions.ImplicitObjectCreationWhenTypeIsApparent, new CodeStyleOption2<bool>(true, NotificationOption2.Warning) },
+        };
+
+        await TestInRegularAndScriptAsync(code, expected, options: optionsCollection);
+    }
+
     [Fact]
     public async Task TestIntroduceFieldInExpressionBodiedPropertyGetter()
     {

src/Features/Core/Portable/IntroduceVariable/AbstractIntroduceVariableService.IntroduceVariableCodeAction.cs

@@ -64,7 +64,7 @@ private async Task<Document> GetChangedDocumentCoreAsync(CancellationToken cance
             }
             else if (_isLocal)
             {
-                return _service.IntroduceLocal(_semanticDocument, _expression, _allOccurrences, _isConstant, cancellationToken);
+                return _service.IntroduceLocal(_semanticDocument, Options, _expression, _allOccurrences, _isConstant, cancellationToken);
             }
             else
             {

src/Features/Core/Portable/IntroduceVariable/AbstractIntroduceVariableService.cs

@@ -13,6 +13,7 @@
 using Microsoft.CodeAnalysis.CodeActions;
 using Microsoft.CodeAnalysis.CodeCleanup;
 using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Formatting;
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.LanguageService;
@@ -50,7 +51,7 @@ internal abstract partial class AbstractIntroduceVariableService<TService, TExpr
     protected abstract bool IsExpressionInStaticLocalFunction(TExpressionSyntax expression);
 
     protected abstract Document IntroduceQueryLocal(SemanticDocument document, TExpressionSyntax expression, bool allOccurrences, CancellationToken cancellationToken);
-    protected abstract Document IntroduceLocal(SemanticDocument document, TExpressionSyntax expression, bool allOccurrences, bool isConstant, CancellationToken cancellationToken);
+    protected abstract Document IntroduceLocal(SemanticDocument document, CodeCleanupOptions options, TExpressionSyntax expression, bool allOccurrences, bool isConstant, CancellationToken cancellationToken);
     protected abstract Task<Document> IntroduceFieldAsync(SemanticDocument document, TExpressionSyntax expression, bool allOccurrences, bool isConstant, CancellationToken cancellationToken);
 
     protected abstract int DetermineFieldInsertPosition(TTypeDeclarationSyntax oldDeclaration, TTypeDeclarationSyntax newDeclaration);

src/Features/VisualBasic/Portable/IntroduceVariable/VisualBasicIntroduceVariableService_IntroduceLocal.vb

@@ -6,13 +6,15 @@ Imports System.Threading
 Imports Microsoft.CodeAnalysis
 Imports Microsoft.CodeAnalysis.CodeActions
 Imports Microsoft.CodeAnalysis.Formatting
+Imports Microsoft.CodeAnalysis.CodeCleanup
 Imports Microsoft.CodeAnalysis.VisualBasic
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
 
 Namespace Microsoft.CodeAnalysis.VisualBasic.IntroduceVariable
     Partial Friend Class VisualBasicIntroduceVariableService
         Protected Overrides Function IntroduceLocal(
                 document As SemanticDocument,
+                options As CodeCleanupOptions,
                 expression As ExpressionSyntax,
                 allOccurrences As Boolean,
                 isConstant As Boolean,

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Simplification/CSharpSimplifierOptions.cs

@@ -28,6 +28,7 @@ internal sealed record class CSharpSimplifierOptions : SimplifierOptions, IEquat
     [DataMember] public CodeStyleOption2<bool> AllowEmbeddedStatementsOnSameLine { get; init; } = CodeStyleOption2.TrueWithSilentEnforcement;
     [DataMember] public CodeStyleOption2<PreferBracesPreference> PreferBraces { get; init; } = s_defaultPreferBraces;
     [DataMember] public CodeStyleOption2<bool> PreferThrowExpression { get; init; } = CodeStyleOption2.TrueWithSuggestionEnforcement;
+    [DataMember] public CodeStyleOption2<bool> ImplicitObjectCreationWhenTypeIsApparent { get; init; } = CodeStyleOption2.FalseWithSilentEnforcement;
 
     public CSharpSimplifierOptions()
     {
@@ -43,6 +44,7 @@ public CSharpSimplifierOptions(IOptionsReader options)
         AllowEmbeddedStatementsOnSameLine = options.GetOption(CSharpCodeStyleOptions.AllowEmbeddedStatementsOnSameLine);
         PreferBraces = options.GetOption(CSharpCodeStyleOptions.PreferBraces);
         PreferThrowExpression = options.GetOption(CSharpCodeStyleOptions.PreferThrowExpression);
+        ImplicitObjectCreationWhenTypeIsApparent = options.GetOption(CSharpCodeStyleOptions.ImplicitObjectCreationWhenTypeIsApparent);
     }
 
     public UseVarPreference GetUseVarPreference()