Improve the cases that 'simplify linq' works on (#76079)

src/Analyzers/CSharp/Analyzers/SimplifyLinqExpression/CSharpSimplifyLinqExpressionDiagnosticAnalyzer.cs

@@ -16,9 +16,11 @@ internal sealed class CSharpSimplifyLinqExpressionDiagnosticAnalyzer : AbstractS
 {
     protected override ISyntaxFacts SyntaxFacts => CSharpSyntaxFacts.Instance;
 
+    protected override bool ConflictsWithMemberByNameOnly => false;
+
     protected override IInvocationOperation? TryGetNextInvocationInChain(IInvocationOperation invocation)
-        // In C#, exention methods contain the methods they are being called from in the `this` parameter 
-        // So in the case of A().ExensionB() to get to ExensionB from A we do the following:
+        // In C#, extension methods contain the methods they are being called from in the `this` parameter 
+        // So in the case of A().ExtensionB() to get to ExtensionB from A we do the following:
         => invocation.Parent is IArgumentOperation argument &&
            argument.Parent is IInvocationOperation nextInvocation
                 ? nextInvocation

src/Analyzers/CSharp/Tests/SimplifyLinqExpression/CSharpSimplifyLinqExpressionFixAllTests.cs

@@ -124,7 +124,7 @@ static void M()
                     var test1 = [|test.Where(x => x.Equals('!')).Any()|];
                     var test2 = [|test.Where(x => x.Equals('!')).SingleOrDefault()|];
                     var test3 = [|test.Where(x => x.Equals('!')).Last()|];
-                    var test4 = test.Where(x => x.Equals('!')).Count();
+                    var test4 = [|test.Where(x => x.Equals('!')).Count()|];
                     var test5 = from x in test where x.Equals('!') select x;
                     var test6 = [|test.Where(a => [|a.Where(s => s.Equals("hello")).FirstOrDefault()|].Equals("hello")).FirstOrDefault()|];
                 }
@@ -143,7 +143,7 @@ static void M()
                     var test1 = test.Any(x => x.Equals('!'));
                     var test2 = test.SingleOrDefault(x => x.Equals('!'));
                     var test3 = test.Last(x => x.Equals('!'));
-                    var test4 = test.Where(x => x.Equals('!')).Count();
+                    var test4 = test.Count(x => x.Equals('!'));
                     var test5 = from x in test where x.Equals('!') select x;
                     var test6 = test.FirstOrDefault(a => a.FirstOrDefault(s => s.Equals("hello")).Equals("hello"));
                 }

src/Analyzers/CSharp/Tests/SimplifyLinqExpression/CSharpSimplifyLinqExpressionTests.cs

@@ -473,18 +473,23 @@ static void M()
     }
 
     [Fact]
-    public async Task TestUnsupportedFunction()
+    public async Task TestUnsupportedMethod()
     {
         var source = """
             using System;
             using System.Linq;
+            using System.Collections;
             using System.Collections.Generic;
-            namespace demo
+
+            class Test : IEnumerable<int>
             {
-                class Test
+                public IEnumerator<int> GetEnumerator() => null;
+                IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+                public int Count() => 0;
+
+                void M()
                 {
-                    static List<int> test1 = new List<int> { 3, 12, 4, 6, 20 };
-                    int test2 = test1.Where(x => x > 0).Count();
+                    int test2 = new Test().Where(x => x > 0).Count();
                 }
             }
             """;
@@ -563,4 +568,76 @@ static void Main(string[] args)
                 """
         }.RunAsync();
     }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/71293")]
+    public static async Task TestOffOfObjectCreation()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+                using System.Linq;
+                using System.Collections.Generic;
+
+                class C
+                {
+                    public void Test()
+                    {
+                        int cnt2 = [|new List<string>().Where(x => x.Equals("hello")).Count()|];
+                    }
+                }
+                """,
+            FixedCode = """
+                using System;
+                using System.Linq;
+                using System.Collections.Generic;
+                
+                class C
+                {
+                    public void Test()
+                    {
+                        int cnt2 = new List<string>().Count(x => x.Equals("hello"));
+                    }
+                }
+                """
+        }.RunAsync();
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/71293")]
+    public static async Task TestOffOfFieldReference()
+    {
+        await new VerifyCS.Test
+        {
+            TestCode = """
+                using System;
+                using System.Linq;
+                using System.Collections.Generic;
+
+                class C
+                {
+                    public void Test()
+                    {
+                        int cnt3 = [|s_wordsField.Where(x => x.Equals("hello")).Count()|];
+                    }
+
+                    private static readonly List<string> s_wordsField;
+                }
+                """,
+            FixedCode = """
+                using System;
+                using System.Linq;
+                using System.Collections.Generic;
+                
+                class C
+                {
+                    public void Test()
+                    {
+                        int cnt3 = s_wordsField.Count(x => x.Equals("hello"));
+                    }
+                
+                    private static readonly List<string> s_wordsField;
+                }
+                """
+        }.RunAsync();
+    }
 }

src/Analyzers/Core/Analyzers/SimplifyLinqExpression/AbstractSimplifyLinqExpressionDiagnosticAnalyzer.cs

@@ -17,7 +17,7 @@ internal abstract class AbstractSimplifyLinqExpressionDiagnosticAnalyzer<TInvoca
     where TInvocationExpressionSyntax : SyntaxNode
     where TMemberAccessExpressionSyntax : SyntaxNode
 {
-    private static readonly IImmutableSet<string> s_nonEnumerableReturningLinqMethodNames =
+    private static readonly ImmutableHashSet<string> s_nonEnumerableReturningLinqMethodNames =
         ImmutableHashSet.Create(
             nameof(Enumerable.First),
             nameof(Enumerable.Last),
@@ -30,6 +30,8 @@ internal abstract class AbstractSimplifyLinqExpressionDiagnosticAnalyzer<TInvoca
 
     protected abstract ISyntaxFacts SyntaxFacts { get; }
 
+    protected abstract bool ConflictsWithMemberByNameOnly { get; }
+
     public AbstractSimplifyLinqExpressionDiagnosticAnalyzer()
         : base(IDEDiagnosticIds.SimplifyLinqExpressionDiagnosticId,
                EnforceOnBuildValues.SimplifyLinqExpression,
@@ -49,19 +51,13 @@ protected override void InitializeWorker(AnalysisContext context)
     private void OnCompilationStart(CompilationStartAnalysisContext context)
     {
         if (!TryGetEnumerableTypeSymbol(context.Compilation, out var enumerableType))
-        {
             return;
-        }
 
         if (!TryGetLinqWhereExtensionMethod(enumerableType, out var whereMethodSymbol))
-        {
             return;
-        }
 
         if (!TryGetLinqMethodsThatDoNotReturnEnumerables(enumerableType, out var linqMethodSymbols))
-        {
             return;
-        }
 
         context.RegisterOperationAction(
             context => AnalyzeInvocationOperation(context, enumerableType, whereMethodSymbol, linqMethodSymbols),
@@ -141,12 +137,19 @@ public void AnalyzeInvocationOperation(OperationAnalysisContext context, INamedT
             return;
         }
 
+        // Do not offer to transpose if there is already a method on the collection named the same as the linq extension
+        // method.  This would cause us to call the instance method after the transformation, not the extension method.
         if (!targetTypeSymbol.Equals(enumerableType, SymbolEqualityComparer.Default) &&
             targetTypeSymbol.MemberNames.Contains(name))
         {
-            // Do not offer to transpose if there is already a member on the collection named the same as the linq extension method
-            // example: list.Where(x => x != null).Count() cannot be changed to list.Count(x => x != null) as List<T> already has a member named Count
-            return;
+            // VB conflicts if any member has the same name (like a Count property vs Count extension method).
+            if (this.ConflictsWithMemberByNameOnly)
+                return;
+
+            // C# conflicts only if it is a method as well.  So a Count property will not conflict with a Count
+            // extension method.
+            if (targetTypeSymbol.GetMembers(name).Any(m => m is IMethodSymbol))
+                return;
         }
 
         context.ReportDiagnostic(Diagnostic.Create(Descriptor, nextInvocation.Syntax.GetLocation()));
@@ -161,25 +164,27 @@ bool IsInvocationNonEnumerableReturningLinqMethod(IInvocationOperation invocatio
 
         INamedTypeSymbol? TryGetSymbolOfMemberAccess(IInvocationOperation invocation)
         {
-            if (invocation.Syntax is TInvocationExpressionSyntax invocationNode &&
-                SyntaxFacts.GetExpressionOfInvocationExpression(invocationNode) is TMemberAccessExpressionSyntax memberAccess &&
-                SyntaxFacts.GetExpressionOfMemberAccessExpression(memberAccess) is SyntaxNode expression)
+            if (invocation.Syntax is not TInvocationExpressionSyntax invocationNode ||
+                SyntaxFacts.GetExpressionOfInvocationExpression(invocationNode) is not TMemberAccessExpressionSyntax memberAccess ||
+                SyntaxFacts.GetExpressionOfMemberAccessExpression(memberAccess) is not SyntaxNode expression)
             {
-                return invocation.SemanticModel?.GetTypeInfo(expression).Type as INamedTypeSymbol;
+                return null;
             }
 
-            return null;
+            return invocation.SemanticModel?.GetTypeInfo(expression).Type as INamedTypeSymbol;
         }
 
         string? TryGetMethodName(IInvocationOperation invocation)
         {
-            if (invocation.Syntax is TInvocationExpressionSyntax invocationNode &&
-                SyntaxFacts.GetExpressionOfInvocationExpression(invocationNode) is TMemberAccessExpressionSyntax memberAccess)
+            if (invocation.Syntax is not TInvocationExpressionSyntax invocationNode ||
+                SyntaxFacts.GetExpressionOfInvocationExpression(invocationNode) is not TMemberAccessExpressionSyntax memberAccess)
             {
-                return SyntaxFacts.GetNameOfMemberAccessExpression(memberAccess).GetText().ToString();
+                return null;
             }
 
-            return null;
+            var memberName = SyntaxFacts.GetNameOfMemberAccessExpression(memberAccess);
+            var identifier = SyntaxFacts.GetIdentifierOfSimpleName(memberName);
+            return identifier.ValueText;
         }
     }
 }

src/Analyzers/VisualBasic/Analyzers/SimplifyLinqExpression/VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer.vb

@@ -16,6 +16,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.SimplifyLinqExpression
 
         Protected Overrides ReadOnly Property SyntaxFacts As ISyntaxFacts = VisualBasicSyntaxFacts.Instance
 
+        Protected Overrides ReadOnly Property ConflictsWithMemberByNameOnly As Boolean = True
+
         Protected Overrides Function TryGetNextInvocationInChain(invocation As IInvocationOperation) As IInvocationOperation
             ' Unlike C# in VB exension methods are related in a simple child-parent relationship
             ' so in the case of A().ExensionB() to get from A to ExensionB we just need to get the parent of A

src/Analyzers/VisualBasic/Tests/SimplifyLinqExpression/VisualBasicSimplifyLinqExpressionTests.vb

@@ -5,6 +5,10 @@
 Imports Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions
 Imports Microsoft.CodeAnalysis.SimplifyLinqExpression
 
+Imports VerifyVB = Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions.VisualBasicCodeFixVerifier(Of
+    Microsoft.CodeAnalysis.VisualBasic.SimplifyLinqExpression.VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer,
+    Microsoft.CodeAnalysis.SimplifyLinqExpression.SimplifyLinqExpressionCodeFixProvider)
+
 Namespace Microsoft.CodeAnalysis.VisualBasic.SimplifyLinqExpression
     <Trait(Traits.Feature, Traits.Features.CodeActionsSimplifyLinqExpression)>
     Partial Public Class VisualBasicSimplifyLinqExpressionTests
@@ -41,7 +45,7 @@ Module T
     End Sub
 End Module"
 
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyCodeFixAsync(testCode, fixedCode)
+            Await VerifyVB.VerifyCodeFixAsync(testCode, fixedCode)
         End Function
 
         <Theory>
@@ -66,7 +70,7 @@ Module T
     End Sub
 End Module"
 
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyAnalyzerAsync(testCode)
+            Await VerifyVB.VerifyAnalyzerAsync(testCode)
         End Function
 
         <Theory>
@@ -101,7 +105,7 @@ Module T
         Dim test = (From x In data).{methodName}(Function(x) x = 1)
     End Sub
 End Module"
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyCodeFixAsync(testCode, fixedCode)
+            Await VerifyVB.VerifyCodeFixAsync(testCode, fixedCode)
         End Function
 
         <Theory>
@@ -126,7 +130,7 @@ Module T
     End Sub
 End Module"
 
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyAnalyzerAsync(testCode)
+            Await VerifyVB.VerifyAnalyzerAsync(testCode)
         End Function
 
         <Theory>
@@ -167,7 +171,7 @@ Module T
                               End Function)
     End Sub
 End Module"
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyCodeFixAsync(testCode, fixedCode)
+            Await VerifyVB.VerifyCodeFixAsync(testCode, fixedCode)
         End Function
 
         <Theory>
@@ -192,7 +196,7 @@ Module T
         Dim output = testvar2.Where(Function(x) x = 4).{methodName}()
     End Sub
 End Module"
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyAnalyzerAsync(testCode)
+            Await VerifyVB.VerifyAnalyzerAsync(testCode)
         End Function
 
         <Theory, CombinatorialData>
@@ -237,7 +241,7 @@ Module T
         Dim test1 = test.{firstMethod}(Function(x) x.{secondMethod}(Function(c) c.Equals(""!"")).Equals(""!""))
     End Sub
 End Module"
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyCodeFixAsync(testCode, fixedCode)
+            Await VerifyVB.VerifyCodeFixAsync(testCode, fixedCode)
         End Function
 
         <Theory>
@@ -273,7 +277,7 @@ Module T
     End Sub
 End Module"
 
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyCodeFixAsync(testCode, fixedCode)
+            Await VerifyVB.VerifyCodeFixAsync(testCode, fixedCode)
         End Function
 
         <Theory>
@@ -297,7 +301,7 @@ Module T
         Dim output = testvar1.Where(Function(x) x = 4).{methodName}(Function(x) x <> 1)
     End Sub
 End Module"
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyAnalyzerAsync(testCode)
+            Await VerifyVB.VerifyAnalyzerAsync(testCode)
         End Function
 
         <Fact>
@@ -313,7 +317,7 @@ Module T
         Dim output = testvar1.Where(Function(x) x = 4).Count()
     End Sub
 End Module"
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyAnalyzerAsync(testCode)
+            Await VerifyVB.VerifyAnalyzerAsync(testCode)
         End Function
 
         <Fact>
@@ -342,7 +346,7 @@ Module T
         Dim result = queryableData.Where(Expression.Lambda(Of Func(Of String, Boolean))(predicateBody, pe)).First()
     End Sub
 End Module"
-            Await VisualBasicCodeFixVerifier(Of VisualBasicSimplifyLinqExpressionDiagnosticAnalyzer, SimplifyLinqExpressionCodeFixProvider).VerifyAnalyzerAsync(testCode)
+            Await VerifyVB.VerifyAnalyzerAsync(testCode)
         End Function
     End Class
 End Namespace

src/Workspaces/CSharp/Portable/CodeGeneration/CSharpSyntaxGenerator.cs

@@ -1666,31 +1666,16 @@ private static SyntaxTokenList AsModifierList(Accessibility accessibility, Decla
     {
         using var _ = ArrayBuilder<SyntaxToken>.GetInstance(out var list);
 
-        switch (accessibility)
-        {
-            case Accessibility.Internal:
-                list.Add(InternalKeyword);
-                break;
-            case Accessibility.Public:
-                list.Add(PublicKeyword);
-                break;
-            case Accessibility.Private:
-                list.Add(PrivateKeyword);
-                break;
-            case Accessibility.Protected:
-                list.Add(ProtectedKeyword);
-                break;
-            case Accessibility.ProtectedOrInternal:
-                list.Add(ProtectedKeyword);
-                list.Add(InternalKeyword);
-                break;
-            case Accessibility.ProtectedAndInternal:
-                list.Add(PrivateKeyword);
-                list.Add(ProtectedKeyword);
-                break;
-            case Accessibility.NotApplicable:
-                break;
-        }
+        list.AddRange((IEnumerable<SyntaxToken>)(accessibility switch
+        {
+            Accessibility.Internal => [InternalKeyword],
+            Accessibility.Public => [PublicKeyword],
+            Accessibility.Private => [PrivateKeyword],
+            Accessibility.Protected => [ProtectedKeyword],
+            Accessibility.ProtectedOrInternal => [ProtectedKeyword, InternalKeyword],
+            Accessibility.ProtectedAndInternal => [PrivateKeyword, ProtectedKeyword],
+            _ => [],
+        }));
 
         if (modifiers.IsFile)
             list.Add(FileKeyword);