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Handle cases where 'field' keyword shouldn't generate a field (#60806)
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* Handle cases where 'field' keyword shouldn't generate a field
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@Youssef1313
Youssef1313 authored Apr 28, 2022
1 parent 76f40a3 commit 1bcdda0
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4 changes: 4 additions & 0 deletions src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1573,6 +1573,10 @@ private BoundExpression BindIdentifier(
{
Error(diagnostics, ErrorCode.ERR_FieldKeywordInsideNameOf, node);
}
else if (backingField.ContainingType.IsInterface && !backingField.IsStatic)
{
Error(diagnostics, ErrorCode.ERR_InterfacesCantContainFields, node);
}
}
}
}
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195 changes: 195 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/PropertyFieldKeywordTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,201 @@ private void VerifyTypeIL(CSharpCompilation compilation, string typeName, string
CompileAndVerify(compilation).VerifyTypeIL(typeName, expected);
}

[Fact]
public void TestInInterface()
{
var comp = CreateCompilation(@"
public interface I
{
public int P1 { get => field; }
public int P2 { get => field; set => field = value; }
public int P3 { get { _ = field; return field; } set => field = value; }
public int P4 { get => field; } = 0;
public int P5 { get => field; set => field = value; } = 0;
public int P6 { get { _ = field; return field; } set => field = value; } = 0;
}
", targetFramework: TargetFramework.NetCoreApp); // setting TargetFramework for DefaultImplementationsOfInterfaces to exist.

var accessorBindingData = new SourcePropertySymbolBase.AccessorBindingData();
comp.TestOnlyCompilationData = accessorBindingData;
comp.VerifyDiagnostics(
// (4,28): error CS0525: Interfaces cannot contain instance fields
// public int P1 { get => field; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(4, 28),
// (6,28): error CS0525: Interfaces cannot contain instance fields
// public int P2 { get => field; set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(6, 28),
// (6,42): error CS0525: Interfaces cannot contain instance fields
// public int P2 { get => field; set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(6, 42),
// (8,31): error CS0525: Interfaces cannot contain instance fields
// public int P3 { get { _ = field; return field; } set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(8, 31),
// (8,45): error CS0525: Interfaces cannot contain instance fields
// public int P3 { get { _ = field; return field; } set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(8, 45),
// (8,61): error CS0525: Interfaces cannot contain instance fields
// public int P3 { get { _ = field; return field; } set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(8, 61),
// (10,16): error CS8053: Instance properties in interfaces cannot have initializers.
// public int P4 { get => field; } = 0;
Diagnostic(ErrorCode.ERR_InstancePropertyInitializerInInterface, "P4").WithArguments("I.P4").WithLocation(10, 16),
// (10,28): error CS0525: Interfaces cannot contain instance fields
// public int P4 { get => field; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(10, 28),
// (12,16): error CS8053: Instance properties in interfaces cannot have initializers.
// public int P5 { get => field; set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InstancePropertyInitializerInInterface, "P5").WithArguments("I.P5").WithLocation(12, 16),
// (12,28): error CS0525: Interfaces cannot contain instance fields
// public int P5 { get => field; set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(12, 28),
// (12,42): error CS0525: Interfaces cannot contain instance fields
// public int P5 { get => field; set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(12, 42),
// (14,16): error CS8053: Instance properties in interfaces cannot have initializers.
// public int P6 { get { _ = field; return field; } set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InstancePropertyInitializerInInterface, "P6").WithArguments("I.P6").WithLocation(14, 16),
// (14,31): error CS0525: Interfaces cannot contain instance fields
// public int P6 { get { _ = field; return field; } set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(14, 31),
// (14,45): error CS0525: Interfaces cannot contain instance fields
// public int P6 { get { _ = field; return field; } set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(14, 45),
// (14,61): error CS0525: Interfaces cannot contain instance fields
// public int P6 { get { _ = field; return field; } set => field = value; } = 0;
Diagnostic(ErrorCode.ERR_InterfacesCantContainFields, "field").WithLocation(14, 61)
);
var @interface = comp.GetTypeByMetadataName("I");
Assert.Empty(@interface.GetMembers().OfType<FieldSymbol>());
var fieldsToEmit = @interface.GetFieldsToEmit().ToArray();
Assert.Equal(6, fieldsToEmit.Length);
Assert.Equal("System.Int32 I.<P1>k__BackingField", fieldsToEmit[0].ToTestDisplayString());
Assert.Equal("System.Int32 I.<P2>k__BackingField", fieldsToEmit[1].ToTestDisplayString());
Assert.Equal("System.Int32 I.<P3>k__BackingField", fieldsToEmit[2].ToTestDisplayString());
Assert.Equal("System.Int32 I.<P4>k__BackingField", fieldsToEmit[3].ToTestDisplayString());
Assert.Equal("System.Int32 I.<P5>k__BackingField", fieldsToEmit[4].ToTestDisplayString());
Assert.Equal("System.Int32 I.<P6>k__BackingField", fieldsToEmit[5].ToTestDisplayString());
Assert.Equal(0, accessorBindingData.NumberOfPerformedAccessorBinding);
}

[Fact]
public void TestStaticInInterface()
{
var comp = CreateCompilation(@"
public interface I
{
public static int P { get => field; }
}
", targetFramework: TargetFramework.NetCoreApp); // setting TargetFramework for DefaultImplementationsOfInterfaces to exist.

var accessorBindingData = new SourcePropertySymbolBase.AccessorBindingData();
comp.TestOnlyCompilationData = accessorBindingData;
comp.VerifyDiagnostics();
VerifyTypeIL(comp, "I", @"
.class interface public auto ansi abstract I
{
// Fields
.field private static initonly int32 '<P>k__BackingField'
.custom instance void [System.Runtime]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (
01 00 00 00
)
// Methods
.method public hidebysig specialname static
int32 get_P () cil managed
{
// Method begins at RVA 0x2050
// Code size 6 (0x6)
.maxstack 8
IL_0000: ldsfld int32 I::'<P>k__BackingField'
IL_0005: ret
} // end of method I::get_P
// Properties
.property int32 P()
{
.get int32 I::get_P()
}
} // end of class I
");
var @interface = comp.GetTypeByMetadataName("I");
Assert.Equal("System.Int32 I.<P>k__BackingField", @interface.GetFieldsToEmit().Single().ToTestDisplayString());
Assert.Empty(@interface.GetMembers().OfType<FieldSymbol>());
Assert.Equal(0, accessorBindingData.NumberOfPerformedAccessorBinding);
}

[Fact]
public void TestStaticInInterface_DefaultImplementationsOfInterfacesIsMissing()
{
var comp = CreateCompilation(@"
public interface I
{
public static int P { get => field; }
}
");
comp.MakeMemberMissing(SpecialMember.System_Runtime_CompilerServices_RuntimeFeature__DefaultImplementationsOfInterfaces);
var accessorBindingData = new SourcePropertySymbolBase.AccessorBindingData();
comp.TestOnlyCompilationData = accessorBindingData;
comp.VerifyDiagnostics(
// (4,27): error CS8701: Target runtime doesn't support default interface implementation.
// public static int P { get => field; }
Diagnostic(ErrorCode.ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation, "get").WithLocation(4, 27)
);
var @interface = comp.GetTypeByMetadataName("I");
Assert.Equal("System.Int32 I.<P>k__BackingField", @interface.GetFieldsToEmit().Single().ToTestDisplayString());
Assert.Empty(@interface.GetMembers().OfType<FieldSymbol>());
Assert.Equal(0, accessorBindingData.NumberOfPerformedAccessorBinding);
}

[Fact]
public void TestAbstract()
{
var comp = CreateCompilation(@"
public abstract class C
{
public abstract int P { get => field; }
}
"); // setting TargetFramework for DefaultImplementationsOfInterfaces to exist.

var accessorBindingData = new SourcePropertySymbolBase.AccessorBindingData();
comp.TestOnlyCompilationData = accessorBindingData;
comp.VerifyDiagnostics(
// (4,29): error CS0500: 'C.P.get' cannot declare a body because it is marked abstract
// public abstract int P { get => field; }
Diagnostic(ErrorCode.ERR_AbstractHasBody, "get").WithArguments("C.P.get").WithLocation(4, 29)
);
var @class = comp.GetTypeByMetadataName("C");
Assert.Empty(@class.GetMembers().OfType<FieldSymbol>());
Assert.Empty(@class.GetFieldsToEmit());
Assert.Equal(0, accessorBindingData.NumberOfPerformedAccessorBinding);
}

[Fact]
public void TestExtern()
{
var comp = CreateCompilation(@"
public class C
{
public extern int P { get => field; }
}
");

var accessorBindingData = new SourcePropertySymbolBase.AccessorBindingData();
comp.TestOnlyCompilationData = accessorBindingData;
comp.VerifyDiagnostics(
// (4,27): error CS0179: 'C.P.get' cannot be extern and declare a body
// public extern int P { get => field; }
Diagnostic(ErrorCode.ERR_ExternHasBody, "get").WithArguments("C.P.get").WithLocation(4, 27)
);
var @class = comp.GetTypeByMetadataName("C");
Assert.Empty(@class.GetMembers().OfType<FieldSymbol>());
Assert.Empty(@class.GetFieldsToEmit());
Assert.Equal(0, accessorBindingData.NumberOfPerformedAccessorBinding);
}

[Fact]
public void TestNameOfFieldInAttribute()
{
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