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Allow ref structs to implement interfaces, respect "allows ref struct" during constraints check. #72537

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merged 2 commits into from
Mar 15, 2024
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Allow ref structs to implement interfaces, respect "allows ref struct" during constraints check. #72537

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Allow ref structs to implement interfaces, respect "allows refg struc…
AlekseyTs Mar 14, 2024
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AlekseyTs Mar 14, 2024
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16 changes: 13 additions & 3 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 @@ -8282,10 +8282,14 @@ private void CheckReceiverAndRuntimeSupportForSymbolAccess(SyntaxNode node, Boun
}
}

if (!Compilation.Assembly.RuntimeSupportsDefaultInterfaceImplementation && Compilation.SourceModule != symbol.ContainingModule)
if (receiverOpt is { Type: TypeParameterSymbol { AllowByRefLike: true } } &&
isNotImplementableInstanceMember(symbol))
{
if (!symbol.IsStatic && !(symbol is TypeSymbol) &&
!symbol.IsImplementableInterfaceMember())
Error(diagnostics, ErrorCode.ERR_BadNonVirtualInterfaceMemberAccessOnAllowsRefLike, node);
}
else if (!Compilation.Assembly.RuntimeSupportsDefaultInterfaceImplementation && Compilation.SourceModule != symbol.ContainingModule)
{
if (isNotImplementableInstanceMember(symbol))
{
Error(diagnostics, ErrorCode.ERR_RuntimeDoesNotSupportDefaultInterfaceImplementation, node);
}
Expand All @@ -8303,6 +8307,12 @@ private void CheckReceiverAndRuntimeSupportForSymbolAccess(SyntaxNode node, Boun
}
}
}

static bool isNotImplementableInstanceMember(Symbol symbol)
{
return !symbol.IsStatic && !(symbol is TypeSymbol) &&
!symbol.IsImplementableInterfaceMember();
}
}

private BoundExpression BindEventAccess(
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5 changes: 5 additions & 0 deletions src/Compilers/CSharp/Portable/Binder/Semantics/Conversions/ConversionsBase.cs
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Expand Up @@ -2921,6 +2921,11 @@ private bool HasImplicitEffectiveInterfaceSetConversion(TypeParameterSymbol sour
}

private bool HasAnyBaseInterfaceConversion(TypeSymbol derivedType, TypeSymbol baseType, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
return ImplementsVarianceCompatibleInterface(derivedType, baseType, ref useSiteInfo);
}

internal bool ImplementsVarianceCompatibleInterface(TypeSymbol derivedType, TypeSymbol baseType, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
Debug.Assert((object)derivedType != null);
Debug.Assert((object)baseType != null);
Expand Down
12 changes: 9 additions & 3 deletions src/Compilers/CSharp/Portable/CSharpResources.resx
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Expand Up @@ -2105,9 +2105,6 @@ If such a class is used as a base class and if the deriving class defines a dest
<data name="ERR_StaticClassInterfaceImpl" xml:space="preserve">
<value>'{0}': static classes cannot implement interfaces</value>
</data>
<data name="ERR_RefStructInterfaceImpl" xml:space="preserve">
<value>'{0}': ref structs cannot implement interfaces</value>
</data>
<data name="ERR_OperatorInStaticClass" xml:space="preserve">
<value>'{0}': static classes cannot contain user-defined operators</value>
</data>
Expand Down Expand Up @@ -7917,4 +7914,13 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
<data name="ERR_ClassIsCombinedWithRefStruct" xml:space="preserve">
<value>Cannot allow ref structs for a type parameter known from other constraints to be a class</value>
</data>
<data name="ERR_NotRefStructConstraintNotSatisfied" xml:space="preserve">
<value>The type '{2}' may not be a ref struct or a type parameter allowing ref structs in order to use it as parameter '{1}' in the generic type or method '{0}'</value>
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@cston cston Mar 14, 2024 •
edited by AlekseyTs
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The type '{2}' may not be a ref struct or a type parameter allowing ref structs in order to use it as parameter '{1}' in the generic type or method '{0}'

Perhaps: "The type ... must not be a ref struct ... in order to use it as type parameter ..." #Resolved

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For "may not be a", I think I used the following message as a template:

  <data name="ERR_LambdaInIsAs" xml:space="preserve">
    <value>The first operand of an 'is' or 'as' operator may not be a lambda expression, anonymous method, or method group.</value>
  </data>

For "in order to use it as parameter", there is a "prior art" too:

  <data name="ERR_RefConstraintNotSatisfied" xml:space="preserve">
    <value>The type '{2}' must be a reference type in order to use it as parameter '{1}' in the generic type or method '{0}'</value>
  </data>

I can make the suggested change if you still think it is needed. Please let me know.

</data>
<data name="ERR_RefStructDoesNotSupportDefaultInterfaceImplementationForMember" xml:space="preserve">
<value>'{0}' cannot implement interface member '{1}' for ref struct '{2}'.</value>
</data>
<data name="ERR_BadNonVirtualInterfaceMemberAccessOnAllowsRefLike" xml:space="preserve">
<value>A non-virtual instance interface member cannot be accessed on a type parameter that allows ref struct.</value>
</data>
</root>
5 changes: 4 additions & 1 deletion src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
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Expand Up @@ -1528,7 +1528,7 @@ internal enum ErrorCode
ERR_FieldsInRoStruct = 8340,
ERR_AutoPropsInRoStruct = 8341,
ERR_FieldlikeEventsInRoStruct = 8342,
ERR_RefStructInterfaceImpl = 8343,
// ERR_RefStructInterfaceImpl = 8343,
ERR_BadSpecialByRefIterator = 8344,
ERR_FieldAutoPropCantBeByRefLike = 8345,
ERR_StackAllocConversionNotPossible = 8346,
Expand Down Expand Up @@ -2304,6 +2304,9 @@ internal enum ErrorCode
ERR_RefStructConstraintAlreadySpecified = 9501,
ERR_AllowsClauseMustBeLast = 9502,
ERR_ClassIsCombinedWithRefStruct = 9503,
ERR_NotRefStructConstraintNotSatisfied = 9504,
ERR_RefStructDoesNotSupportDefaultInterfaceImplementationForMember = 9505,
ERR_BadNonVirtualInterfaceMemberAccessOnAllowsRefLike = 9506,

#endregion

Expand Down
4 changes: 3 additions & 1 deletion src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs
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Expand Up @@ -1839,7 +1839,6 @@ internal static bool IsBuildOnlyDiagnostic(ErrorCode code)
case ErrorCode.ERR_FieldsInRoStruct:
case ErrorCode.ERR_AutoPropsInRoStruct:
case ErrorCode.ERR_FieldlikeEventsInRoStruct:
case ErrorCode.ERR_RefStructInterfaceImpl:
case ErrorCode.ERR_BadSpecialByRefIterator:
case ErrorCode.ERR_FieldAutoPropCantBeByRefLike:
case ErrorCode.ERR_StackAllocConversionNotPossible:
Expand Down Expand Up @@ -2434,6 +2433,9 @@ internal static bool IsBuildOnlyDiagnostic(ErrorCode code)
case ErrorCode.ERR_RefStructConstraintAlreadySpecified:
case ErrorCode.ERR_AllowsClauseMustBeLast:
case ErrorCode.ERR_ClassIsCombinedWithRefStruct:
case ErrorCode.ERR_NotRefStructConstraintNotSatisfied:
case ErrorCode.ERR_RefStructDoesNotSupportDefaultInterfaceImplementationForMember:
case ErrorCode.ERR_BadNonVirtualInterfaceMemberAccessOnAllowsRefLike:
return false;
default:
// NOTE: All error codes must be explicitly handled in this switch statement
Expand Down
45 changes: 38 additions & 7 deletions src/Compilers/CSharp/Portable/Symbols/ConstraintsHelper.cs
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Expand Up @@ -927,13 +927,37 @@ private static bool CheckBasicConstraints(
ArrayBuilder<TypeParameterDiagnosticInfo> nullabilityDiagnosticsBuilderOpt,
ref ArrayBuilder<TypeParameterDiagnosticInfo> useSiteDiagnosticsBuilder)
{
if (typeArgument.Type.IsPointerOrFunctionPointer() || typeArgument.IsRestrictedType() || typeArgument.IsVoidType())
if (typeArgument.Type.IsPointerOrFunctionPointer() || typeArgument.IsRestrictedType(ignoreSpanLikeTypes: true) || typeArgument.IsVoidType())
{
// "The type '{0}' may not be used as a type argument"
diagnosticsBuilder.Add(new TypeParameterDiagnosticInfo(typeParameter, new UseSiteInfo<AssemblySymbol>(new CSDiagnosticInfo(ErrorCode.ERR_BadTypeArgument, typeArgument.Type))));
return false;
}

if (typeArgument.IsRefLikeType() || typeArgument.Type is TypeParameterSymbol { AllowByRefLike: true })
{
if (typeParameter.AllowByRefLike)
{
if (args.CurrentCompilation.SourceModule != typeParameter.ContainingModule)
{
if (MessageID.IDS_FeatureRefStructInterfaces.GetFeatureAvailabilityDiagnosticInfo(args.CurrentCompilation) is { } diagnosticInfo)
{
diagnosticsBuilder.Add(new TypeParameterDiagnosticInfo(typeParameter, new UseSiteInfo<AssemblySymbol>(diagnosticInfo)));
}

if (!args.CurrentCompilation.Assembly.RuntimeSupportsByRefLikeGenerics)
{
diagnosticsBuilder.Add(new TypeParameterDiagnosticInfo(typeParameter, new UseSiteInfo<AssemblySymbol>(new CSDiagnosticInfo(ErrorCode.ERR_RuntimeDoesNotSupportByRefLikeGenerics))));
}
}
}
else
{
diagnosticsBuilder.Add(new TypeParameterDiagnosticInfo(typeParameter, new UseSiteInfo<AssemblySymbol>(new CSDiagnosticInfo(ErrorCode.ERR_NotRefStructConstraintNotSatisfied, containingSymbol.ConstructedFrom(), typeParameter, typeArgument.Type))));
return false;
}
}

if (typeArgument.IsStatic)
{
// "'{0}': static types cannot be used as type arguments"
Expand Down Expand Up @@ -1307,13 +1331,20 @@ private static bool SatisfiesConstraintType(
return true;
}

// "... A boxing conversion (6.1.7), provided that type A is a non-nullable value type. ..."
// NOTE: we extend this to allow, for example, a conversion from Nullable<T> to object.
if (typeArgument.Type.IsValueType &&
conversions.HasBoxingConversion(typeArgument.Type.IsNullableType() ? ((NamedTypeSymbol)typeArgument.Type).ConstructedFrom : typeArgument.Type,
constraintType.Type, ref useSiteInfo))
if (typeArgument.Type.IsValueType)
{
return true;
// "... A boxing conversion (6.1.7), provided that type A is a non-nullable value type. ..."
// NOTE: we extend this to allow, for example, a conversion from Nullable<T> to object.
if (conversions.HasBoxingConversion(typeArgument.Type.IsNullableType() ? ((NamedTypeSymbol)typeArgument.Type).ConstructedFrom : typeArgument.Type,
constraintType.Type, ref useSiteInfo))
{
return true;
}

if (typeArgument.Type.IsRefLikeType && conversions.ImplementsVarianceCompatibleInterface(typeArgument.Type, constraintType.Type, ref useSiteInfo))
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@jjonescz jjonescz Mar 15, 2024 •
edited by AlekseyTs
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Why is this check needed specifically for ref struct type arguments - i.e., why they need different handling then normal structs for example? #Resolved

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Why is this check needed specifically for ref struct type arguments - i.e., why they need different handling then normal structs for example?

There are no boxing conversion for ref structs, therefore, the conversions.HasBoxingConversion check above fails.

{
return true;
}
}

if (typeArgument.TypeKind == TypeKind.TypeParameter)
Expand Down
3 changes: 1 addition & 2 deletions src/Compilers/CSharp/Portable/Symbols/Source/SourceNamedTypeSymbol_Bases.cs
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Expand Up @@ -569,8 +569,7 @@ private Tuple<NamedTypeSymbol, ImmutableArray<NamedTypeSymbol>> MakeOneDeclaredB

if (this.IsRefLikeType)
{
// '{0}': ref structs cannot implement interfaces
diagnostics.Add(ErrorCode.ERR_RefStructInterfaceImpl, location, this);
Binder.CheckFeatureAvailability(typeSyntax, MessageID.IDS_FeatureRefStructInterfaces, diagnostics);
}

if (baseType.ContainsDynamic())
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1 change: 1 addition & 0 deletions src/Compilers/CSharp/Portable/Symbols/SymbolExtensions.cs
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Expand Up @@ -201,6 +201,7 @@ public static Symbol ConstructedFrom(this Symbol symbol)
switch (symbol.Kind)
{
case SymbolKind.NamedType:
case SymbolKind.ErrorType:
return ((NamedTypeSymbol)symbol).ConstructedFrom;

case SymbolKind.Method:
Expand Down
52 changes: 31 additions & 21 deletions src/Compilers/CSharp/Portable/Symbols/TypeSymbol.cs
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Expand Up @@ -1618,34 +1618,44 @@ private static void CheckForImplementationOfCorrespondingPropertyOrEvent(MethodS

private static void ReportDefaultInterfaceImplementationMatchDiagnostics(Symbol interfaceMember, TypeSymbol implementingType, Symbol implicitImpl, BindingDiagnosticBag diagnostics)
{
if (interfaceMember.Kind == SymbolKind.Method && implementingType.ContainingModule != implicitImpl.ContainingModule)
if (interfaceMember.Kind == SymbolKind.Method)
{
// The default implementation is coming from a different module, which means that we probably didn't check
// for the required runtime capability or language version
bool isStatic = implicitImpl.IsStatic;
var feature = isStatic ? MessageID.IDS_FeatureStaticAbstractMembersInInterfaces : MessageID.IDS_DefaultInterfaceImplementation;

LanguageVersion requiredVersion = feature.RequiredVersion();
LanguageVersion? availableVersion = implementingType.DeclaringCompilation?.LanguageVersion;
if (requiredVersion > availableVersion)
if (!isStatic && implementingType.IsRefLikeType)
{
diagnostics.Add(ErrorCode.ERR_LanguageVersionDoesNotSupportInterfaceImplementationForMember,
diagnostics.Add(ErrorCode.ERR_RefStructDoesNotSupportDefaultInterfaceImplementationForMember,
GetInterfaceLocation(interfaceMember, implementingType),
implicitImpl, interfaceMember, implementingType,
feature.Localize(),
availableVersion.GetValueOrDefault().ToDisplayString(),
new CSharpRequiredLanguageVersion(requiredVersion));
implicitImpl, interfaceMember, implementingType);
}

if (!(isStatic ?
implementingType.ContainingAssembly.RuntimeSupportsStaticAbstractMembersInInterfaces :
implementingType.ContainingAssembly.RuntimeSupportsDefaultInterfaceImplementation))
else if (implementingType.ContainingModule != implicitImpl.ContainingModule)
{
diagnostics.Add(isStatic ?
ErrorCode.ERR_RuntimeDoesNotSupportStaticAbstractMembersInInterfacesForMember :
ErrorCode.ERR_RuntimeDoesNotSupportDefaultInterfaceImplementationForMember,
GetInterfaceLocation(interfaceMember, implementingType),
implicitImpl, interfaceMember, implementingType);
// The default implementation is coming from a different module, which means that we probably didn't check
// for the required runtime capability or language version
var feature = isStatic ? MessageID.IDS_FeatureStaticAbstractMembersInInterfaces : MessageID.IDS_DefaultInterfaceImplementation;

LanguageVersion requiredVersion = feature.RequiredVersion();
LanguageVersion? availableVersion = implementingType.DeclaringCompilation?.LanguageVersion;
if (requiredVersion > availableVersion)
{
diagnostics.Add(ErrorCode.ERR_LanguageVersionDoesNotSupportInterfaceImplementationForMember,
GetInterfaceLocation(interfaceMember, implementingType),
implicitImpl, interfaceMember, implementingType,
feature.Localize(),
availableVersion.GetValueOrDefault().ToDisplayString(),
new CSharpRequiredLanguageVersion(requiredVersion));
}

if (!(isStatic ?
implementingType.ContainingAssembly.RuntimeSupportsStaticAbstractMembersInInterfaces :
implementingType.ContainingAssembly.RuntimeSupportsDefaultInterfaceImplementation))
{
diagnostics.Add(isStatic ?
ErrorCode.ERR_RuntimeDoesNotSupportStaticAbstractMembersInInterfacesForMember :
ErrorCode.ERR_RuntimeDoesNotSupportDefaultInterfaceImplementationForMember,
GetInterfaceLocation(interfaceMember, implementingType),
implicitImpl, interfaceMember, implementingType);
}
}
}
}
Expand Down
20 changes: 15 additions & 5 deletions src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf
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