Disallow declaration of indexers in absence of proper DefaultMemberAt…

…tribute. (#75099) Fixes #75032.
dotnet · Sep 30, 2024 · ba7fe35 · ba7fe35
1 parent 3c1810f
commit ba7fe35
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diff --git a/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 9.md b/docs/compilers/CSharp/Compiler Breaking Changes - DotNet 9.md
@@ -93,3 +93,15 @@ class C
     }
 }
 ```
+
+
+## Declaration of indexers in absence of proper declaration of DefaultMemberAttribute is no longer allowed.
+
+***Introduced in Visual Studio 2022 version 17.13***
+
+```cs
+public interface I1
+{
+    public I1 this[I1 args] { get; } // error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+}
+```
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamedTypeSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceNamedTypeSymbol.cs
@@ -1796,27 +1796,30 @@ protected override void AfterMembersCompletedChecks(BindingDiagnosticBag diagnos
             Debug.Assert(ObsoleteKind != ObsoleteAttributeKind.Uninitialized);
             Debug.Assert(GetMembers().All(m => m.ObsoleteKind != ObsoleteAttributeKind.Uninitialized));
 
-            if (ObsoleteKind != ObsoleteAttributeKind.None
-                || GetMembers().All(m => m is not MethodSymbol { MethodKind: MethodKind.Constructor, ObsoleteKind: ObsoleteAttributeKind.None } method
+            if (ObsoleteKind == ObsoleteAttributeKind.None
+                && !GetMembers().All(m => m is not MethodSymbol { MethodKind: MethodKind.Constructor, ObsoleteKind: ObsoleteAttributeKind.None } method
                                          || !method.ShouldCheckRequiredMembers()))
             {
-                return;
-            }
-
-            foreach (var member in GetMembers())
-            {
-                if (!member.IsRequired())
+                foreach (var member in GetMembers())
                 {
-                    continue;
-                }
+                    if (!member.IsRequired())
+                    {
+                        continue;
+                    }
 
-                if (member.ObsoleteKind != ObsoleteAttributeKind.None)
-                {
-                    // Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.
-                    diagnostics.Add(ErrorCode.WRN_ObsoleteMembersShouldNotBeRequired, member.GetFirstLocation(), member);
+                    if (member.ObsoleteKind != ObsoleteAttributeKind.None)
+                    {
+                        // Required member '{0}' should not be attributed with 'ObsoleteAttribute' unless the containing type is obsolete or all constructors are obsolete.
+                        diagnostics.Add(ErrorCode.WRN_ObsoleteMembersShouldNotBeRequired, member.GetFirstLocation(), member);
+                    }
                 }
             }
 
+            if (Indexers.FirstOrDefault() is PropertySymbol indexerSymbol)
+            {
+                Binder.GetWellKnownTypeMember(DeclaringCompilation, WellKnownMember.System_Reflection_DefaultMemberAttribute__ctor, diagnostics, indexerSymbol.TryGetFirstLocation() ?? GetFirstLocation());
+            }
+
             if (TypeKind == TypeKind.Struct && !IsRecordStruct && HasInlineArrayAttribute(out _))
             {
                 if (Layout.Kind == LayoutKind.Explicit)

diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/IndexerTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/IndexerTests.cs
@@ -9,6 +9,7 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.CSharp.UnitTests.Emit;
+using Microsoft.CodeAnalysis.Test.Utilities;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Test.Utilities;
 using Xunit;
@@ -1185,5 +1186,80 @@ static void Main()
         }
 
         #endregion Lowering
+
+        [Fact]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/75032")]
+        public void MissingDefaultMemberAttribute_01()
+        {
+            var text1 = @"
+public interface I1
+{
+    public I1 this[I1 args] { get; }
+}
+";
+            var comp1 = CreateCompilation(text1);
+            comp1.MakeMemberMissing(WellKnownMember.System_Reflection_DefaultMemberAttribute__ctor);
+
+            comp1.VerifyDiagnostics(
+                // (4,15): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public I1 this[I1 args] { get; }
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(4, 15)
+                );
+
+            comp1 = CreateCompilation(text1);
+            comp1.MakeTypeMissing(WellKnownType.System_Reflection_DefaultMemberAttribute);
+
+            comp1.VerifyDiagnostics(
+                // (4,15): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public I1 this[I1 args] { get; }
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(4, 15)
+                );
+
+            comp1 = CreateCompilation(text1);
+            comp1.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/75032")]
+        public void MissingDefaultMemberAttribute_02()
+        {
+            var text1 = @"
+public interface I1
+{
+    public I1 this[I1 args] { get; }
+}
+";
+            var comp1 = CreateCompilation(text1);
+
+            var text2 = @"
+class C : I1
+{
+    I1 I1.this[I1 args] => throw null;
+}
+";
+            var comp2 = CreateCompilation(text2, references: [comp1.ToMetadataReference()]);
+            comp2.MakeMemberMissing(WellKnownMember.System_Reflection_DefaultMemberAttribute__ctor);
+            comp2.VerifyEmitDiagnostics();
+        }
+
+        [Fact]
+        [WorkItem("https://github.com/dotnet/roslyn/issues/75032")]
+        public void MissingDefaultMemberAttribute_03()
+        {
+            var text1 = @"
+using System.Collections.Generic;
+
+class Program
+{
+    static IEnumerable<int> Test()
+    {
+        return [123];
+    }
+}
+";
+            var comp1 = CreateCompilation(text1);
+            comp1.MakeMemberMissing(WellKnownMember.System_Reflection_DefaultMemberAttribute__ctor);
+            CompileAndVerify(comp1).VerifyDiagnostics();
+        }
     }
 }
diff --git a/src/Compilers/CSharp/Test/Emit/Emit/InAttributeModifierTests.cs b/src/Compilers/CSharp/Test/Emit/Emit/InAttributeModifierTests.cs
@@ -1565,6 +1565,9 @@ class Test
 }";
 
             CreateEmptyCompilation(code).VerifyDiagnostics(
+                // (9,27): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public virtual object this[in object p] => null;
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(9, 27),
                 // (9,32): error CS0518: Predefined type 'System.Runtime.InteropServices.InAttribute' is not defined or imported
                 //     public virtual object this[in object p] => null;
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "in object p").WithArguments("System.Runtime.InteropServices.InAttribute").WithLocation(9, 32));
@@ -1588,7 +1591,11 @@ class Test
             CreateEmptyCompilation(code).VerifyDiagnostics(
                 // (10,20): error CS0518: Predefined type 'System.Runtime.InteropServices.InAttribute' is not defined or imported
                 //     public virtual ref readonly object this[object p] => ref value;
-                Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "ref readonly object").WithArguments("System.Runtime.InteropServices.InAttribute").WithLocation(10, 20));
+                Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "ref readonly object").WithArguments("System.Runtime.InteropServices.InAttribute").WithLocation(10, 20),
+                // (10,40): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public virtual ref readonly object this[object p] => ref value;
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(10, 40)
+                );
         }
 
         [Fact]

diff --git a/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IArgument.cs b/src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_IArgument.cs
@@ -2588,6 +2588,9 @@ void M1()
                 // (6,37): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     public int this[int x, int? y = 5]
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "5").WithArguments("System.Int32").WithLocation(6, 37),
+                // (6,16): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public int this[int x, int? y = 5]
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(6, 16),
                 // (5,27): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     private int _number = 0;
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "0").WithArguments("System.Int32").WithLocation(5, 27),
@@ -2766,6 +2769,9 @@ void M1()
                 // (5,12): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     public int this[int x, int? y = null]
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "int").WithArguments("System.Int32").WithLocation(5, 12),
+                // (5,16): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public int this[int x, int? y = null]
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(5, 16),
                 // (5,21): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     public int this[int x, int? y = null]
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "int").WithArguments("System.Int32").WithLocation(5, 21),
@@ -3829,6 +3835,9 @@ P M1()
                 // (5,37): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     public int this[int x, int? y = 0]
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "0").WithArguments("System.Int32").WithLocation(5, 37),
+                // (5,16): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public int this[int x, int? y = 0]
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(5, 16),
                 // (4,27): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     private int _number = 0;
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "0").WithArguments("System.Int32").WithLocation(4, 27),
@@ -3903,6 +3912,9 @@ P M1()
                 // (5,12): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     public int this[int x, int? y = null]
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "int").WithArguments("System.Int32").WithLocation(5, 12),
+                // (5,16): error CS0656: Missing compiler required member 'System.Reflection.DefaultMemberAttribute..ctor'
+                //     public int this[int x, int? y = null]
+                Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "this").WithArguments("System.Reflection.DefaultMemberAttribute", ".ctor").WithLocation(5, 16),
                 // (5,21): error CS0518: Predefined type 'System.Int32' is not defined or imported
                 //     public int this[int x, int? y = null]
                 Diagnostic(ErrorCode.ERR_PredefinedTypeNotFound, "int").WithArguments("System.Int32").WithLocation(5, 21),

diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/InitOnlyMemberTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/InitOnlyMemberTests.cs
@@ -4,6 +4,7 @@
 
 #nullable disable
 
+using System.Collections.Immutable;
 using System.Linq;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.CSharp.Symbols.Metadata.PE;
@@ -3462,7 +3463,10 @@ void M(C c)
 ";
 
             var reference = CreateMetadataReferenceFromIlSource(il);
-            var comp = CreateCompilation(source, references: new[] { reference }, parseOptions: TestOptions.Regular9);
+            var comp = CreateCompilation(source, references: new[] { reference }, parseOptions: TestOptions.Regular9,
+                options: TestOptions.ReleaseDll.WithSpecificDiagnosticOptions(
+                    // warning CS1685: The predefined type 'DefaultMemberAttribute' is defined in multiple assemblies
+                    ImmutableDictionary<string, ReportDiagnostic>.Empty.Add("CS1685", ReportDiagnostic.Suppress)));
             comp.VerifyEmitDiagnostics(
                 // (4,25): error CS0569: 'Derived.this[int]': cannot override 'C.this[int]' because it is not supported by the language
                 //     public override int this[int i] { set { throw null; } }
@@ -3558,7 +3562,10 @@ public class Derived2 : C
 ";
 
             var reference = CreateMetadataReferenceFromIlSource(il);
-            var comp = CreateCompilation(source, references: new[] { reference }, parseOptions: TestOptions.Regular9);
+            var comp = CreateCompilation(source, references: new[] { reference }, parseOptions: TestOptions.Regular9,
+                options: TestOptions.ReleaseDll.WithSpecificDiagnosticOptions(
+                    // warning CS1685: The predefined type 'DefaultMemberAttribute' is defined in multiple assemblies
+                    ImmutableDictionary<string, ReportDiagnostic>.Empty.Add("CS1685", ReportDiagnostic.Suppress)));
             comp.VerifyEmitDiagnostics(
                 // (4,39): error CS0570: 'C.this[int].set' is not supported by the language
                 //     public override int this[int i] { set { throw null; } }