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Extension indexers: allow and resolve extension indexers #81607

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Extension indexers: allow and resolve extension indexers #81607

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17 changes: 8 additions & 9 deletions src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,6 @@ internal MethodInfo ReplaceWithExtensionImplementation(out bool wasError)
var setMethod = replace(SetMethod);
Symbol symbol = ReferenceEquals(Symbol, Method) && method is not null ? method : Symbol;

Debug.Assert(SetMethod?.IsExtensionBlockMember() != true);
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@AlekseyTs AlekseyTs Dec 10, 2025

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Debug.Assert(SetMethod?.IsExtensionBlockMember() != true);

It is not obvious why this condition was correct for properties and isn't for indexers. Is it still worth asserting for properties?

wasError = (Method is not null && method is null) || (SetMethod is not null && setMethod is null);

return new MethodInfo(symbol, method, setMethod);
Expand Down Expand Up @@ -634,10 +633,11 @@ private BoundIndexerAccess BindIndexerDefaultArgumentsAndParamsCollection(BoundI
{
var coreValueKind = valueKind & ValueKindSignificantBitsMask;
AccessorKind accessorKind = GetIndexerAccessorKind(indexerAccess, valueKind);
var useSetAccessor = coreValueKind == BindValueKind.Assignable && indexerAccess.Indexer.RefKind != RefKind.Ref;
PropertySymbol indexer = indexerAccess.Indexer;
var useSetAccessor = coreValueKind == BindValueKind.Assignable && indexer.RefKind != RefKind.Ref;
var accessorForDefaultArguments = useSetAccessor
? indexerAccess.Indexer.GetOwnOrInheritedSetMethod()
: indexerAccess.Indexer.GetOwnOrInheritedGetMethod();
? indexer.GetOwnOrInheritedSetMethod()
: indexer.GetOwnOrInheritedGetMethod();
if (accessorForDefaultArguments is not null)
{
var argumentsBuilder = ArrayBuilder<BoundExpression>.GetInstance(accessorForDefaultArguments.ParameterCount);
Expand All @@ -664,7 +664,7 @@ private BoundIndexerAccess BindIndexerDefaultArgumentsAndParamsCollection(BoundI
}

BitVector defaultArguments = default;
Debug.Assert(parameters.Length == indexerAccess.Indexer.Parameters.Length);
Debug.Assert(parameters.Length == indexer.Parameters.Length);

ImmutableArray<string?> argumentNamesOpt = indexerAccess.ArgumentNamesOpt;

Expand All @@ -690,9 +690,8 @@ private BoundIndexerAccess BindIndexerDefaultArgumentsAndParamsCollection(BoundI
}
}

// Tracked by https://github.com/dotnet/roslyn/issues/78829 : caller info on extension parameter of an extension indexer will need the receiver/argument to be passed
Debug.Assert(!indexerAccess.Indexer.IsExtensionBlockMember());
BindDefaultArguments(indexerAccess.Syntax, parameters, extensionReceiver: null, argumentsBuilder, refKindsBuilderOpt, namesBuilder, ref argsToParams, out defaultArguments, indexerAccess.Expanded, enableCallerInfo: true, diagnostics: diagnostics);
BoundExpression? extensionReceiver = indexer.IsExtensionBlockMember() ? indexerAccess.ReceiverOpt : null;
BindDefaultArguments(indexerAccess.Syntax, parameters, extensionReceiver, argumentsBuilder, refKindsBuilderOpt, namesBuilder, ref argsToParams, out defaultArguments, indexerAccess.Expanded, enableCallerInfo: true, diagnostics: diagnostics);

if (namesBuilder is object)
{
Expand All @@ -704,7 +703,7 @@ private BoundIndexerAccess BindIndexerDefaultArgumentsAndParamsCollection(BoundI
indexerAccess = indexerAccess.Update(
indexerAccess.ReceiverOpt,
indexerAccess.InitialBindingReceiverIsSubjectToCloning,
indexerAccess.Indexer,
indexer,
argumentsBuilder.ToImmutableAndFree(),
argumentNamesOpt,
refKindsBuilderOpt?.ToImmutableOrNull() ?? default,
Expand Down
8 changes: 8 additions & 0 deletions src/Compilers/CSharp/Portable/Binder/Binder.cs
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Expand Up @@ -762,6 +762,14 @@ internal static void ReportDiagnosticsIfDisallowedExtension(BindingDiagnosticBag
}
}

internal static void ReportDiagnosticsIfDisallowedExtensionIndexer(BindingDiagnosticBag diagnostics, PropertySymbol property, SyntaxNode syntax)
{
if (property.IsExtensionBlockMember())
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@AlekseyTs AlekseyTs Dec 10, 2025 •
edited by jcouv
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property

How do we know that this is an indexer? #Pending

{
MessageID.IDS_FeatureExtensionIndexers.CheckFeatureAvailability(diagnostics, syntax);
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@AlekseyTs AlekseyTs Dec 11, 2025 •
edited by jcouv
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MessageID.IDS_FeatureExtensionIndexers.CheckFeatureAvailability(diagnostics, syntax);

Consider skipping the check if the indexer is declared in the same module. We already complained on the declaration #Pending

}
}

internal static void ReportDiagnosticsIfUnmanagedCallersOnly(BindingDiagnosticBag diagnostics, MethodSymbol symbol, SyntaxNodeOrToken syntax, bool isDelegateConversion)
{
var unmanagedCallersOnlyAttributeData = symbol.GetUnmanagedCallersOnlyAttributeData(forceComplete: false);
Expand Down
4 changes: 3 additions & 1 deletion src/Compilers/CSharp/Portable/Binder/Binder_Crefs.cs
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Expand Up @@ -242,6 +242,7 @@ private ImmutableArray<Symbol> BindExtensionMemberCref(ExtensionMemberCrefSyntax
memberName = GetOperatorMethodName(operatorSyntax);
parameters = operatorSyntax.Parameters;
}
// PROTOTYPE handle IndexerMemberCrefSyntax and check for LangVersion

if (memberName == null)
{
Expand Down Expand Up @@ -326,7 +327,8 @@ ImmutableArray<Symbol> computeSortedAndFilteredCrefExtensionMembers(NamespaceOrT

foreach (var candidate in candidates)
{
if (!SourceMemberContainerTypeSymbol.IsAllowedExtensionMember(candidate))
// PROTOTYPE we should find all the members supported in latest LangVer, but report if they require a new LangVer than current
if (!SourceMemberContainerTypeSymbol.IsAllowedExtensionMember(candidate, LanguageVersion.Preview))
{
continue;
}
Expand Down
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