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Fix unsafe context when binding multiple static usings #82427

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Fix unsafe context when binding multiple static usings #82427

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7048428
Fix unsafe context when binding multiple static usings
jjonescz Feb 17, 2026
4ffbb9c
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jjonescz Feb 18, 2026
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25 changes: 19 additions & 6 deletions src/Compilers/CSharp/Portable/Symbols/Source/SourceNamespaceSymbol.AliasesAndUsings.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -641,9 +641,10 @@ UsingsAndDiagnostics buildUsings(
ImmutableDictionary<string, AliasAndUsingDirective>.Builder? usingAliasesMap = null;
ArrayBuilder<AliasAndUsingDirective>? usingAliases = null;

// A binder that contains the extern aliases but not the usings. The resolution of the target of a using directive or alias
// Binders that contain the extern aliases but not the usings. The resolution of the target of a using directive or alias
// should not make use of other peer usings.
Binder? declarationBinder = null;
Binder? declarationBinderSafe = null;
Binder? declarationBinderUnsafe = null; // with UnsafeRegion flag

PooledHashSet<NamespaceOrTypeSymbol>? uniqueUsings = null;
PooledHashSet<NamespaceOrTypeSymbol>? uniqueGlobalUsings = null;
Expand Down Expand Up @@ -732,7 +733,7 @@ UsingsAndDiagnostics buildUsings(
continue;
}

var flags = BinderFlags.SuppressConstraintChecks;
bool needsUnsafeBinder = false;
if (usingDirective.UnsafeKeyword != default)
{
var unsafeKeywordLocation = usingDirective.UnsafeKeyword.GetLocation();
Expand All @@ -746,7 +747,7 @@ UsingsAndDiagnostics buildUsings(
declaringSymbol.CheckUnsafeModifier(DeclarationModifiers.Unsafe, unsafeKeywordLocation, diagnostics);
}

flags |= BinderFlags.UnsafeRegion;
needsUnsafeBinder = true;
}
else
{
Expand All @@ -755,14 +756,26 @@ UsingsAndDiagnostics buildUsings(
// List<int*[]>;` to be written. In 12.0 and onwards though, we require the code to
// explicitly contain the `unsafe` keyword.
if (!compilation.IsFeatureEnabled(MessageID.IDS_FeatureUsingTypeAlias))
flags |= BinderFlags.UnsafeRegion;
needsUnsafeBinder = true;
}

var directiveDiagnostics = BindingDiagnosticBag.GetInstance();
Debug.Assert(directiveDiagnostics.DiagnosticBag is object);
Debug.Assert(directiveDiagnostics.DependenciesBag is object);

declarationBinder ??= compilation.GetBinderFactory(declarationSyntax.SyntaxTree).GetBinder(usingDirective.NamespaceOrType).WithAdditionalFlags(flags);
declarationBinderSafe ??= compilation.GetBinderFactory(declarationSyntax.SyntaxTree).GetBinder(usingDirective.NamespaceOrType).WithAdditionalFlags(BinderFlags.SuppressConstraintChecks);

Binder declarationBinder;
if (needsUnsafeBinder)
{
declarationBinderUnsafe ??= declarationBinderSafe.WithAdditionalFlags(BinderFlags.UnsafeRegion);
declarationBinder = declarationBinderUnsafe;
}
else
{
declarationBinder = declarationBinderSafe;
}

var imported = declarationBinder.BindNamespaceOrTypeSymbol(usingDirective.NamespaceOrType, directiveDiagnostics, basesBeingResolved).NamespaceOrTypeSymbol;
bool addDirectiveDiagnostics = true;

Expand Down
48 changes: 48 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/UnsafeTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -13251,6 +13251,54 @@ unsafe void M2(X t) { }
Diagnostic(ErrorCode.ERR_UnsafeNeeded, "X").WithLocation(6, 13));
}

[Fact]
public void UsingAlias_Multiple()
{
CreateCompilation("""
#pragma warning disable CS8019 // unnecessary using
using unsafe X = System.Collections.Generic.List<int*[]>;
using Y = System.Collections.Generic.List<long*[]>;
""",
options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics(
// (3,43): error CS0214: Pointers and fixed size buffers may only be used in an unsafe context
// using Y = System.Collections.Generic.List<long*[]>;
Diagnostic(ErrorCode.ERR_UnsafeNeeded, "long*").WithLocation(3, 43));

CreateCompilation("""
#pragma warning disable CS8019 // unnecessary using
using X = System.Collections.Generic.List<int*[]>;
using unsafe Y = System.Collections.Generic.List<long*[]>;
""",
options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics(
// (2,43): error CS0214: Pointers and fixed size buffers may only be used in an unsafe context
// using X = System.Collections.Generic.List<int*[]>;
Diagnostic(ErrorCode.ERR_UnsafeNeeded, "int*").WithLocation(2, 43));
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/82426")]
public void UsingStatic_Multiple()
{
CreateCompilation("""
#pragma warning disable CS8019 // unnecessary using
using static unsafe System.Collections.Generic.List<int*[]>;
using static System.Collections.Generic.List<long*[]>;
""",
options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics(
// (3,46): error CS0214: Pointers and fixed size buffers may only be used in an unsafe context
// using static System.Collections.Generic.List<long*[]>;
Diagnostic(ErrorCode.ERR_UnsafeNeeded, "long*").WithLocation(3, 46));

CreateCompilation("""
#pragma warning disable CS8019 // unnecessary using
using static System.Collections.Generic.List<int*[]>;
using static unsafe System.Collections.Generic.List<long*[]>;
""",
options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics(
// (2,46): error CS0214: Pointers and fixed size buffers may only be used in an unsafe context
// using static System.Collections.Generic.List<int*[]>;
Diagnostic(ErrorCode.ERR_UnsafeNeeded, "int*").WithLocation(2, 46));
}

[Fact]
public void TestStructWithReferenceToItselfThroughAliasPointer1()
{
Expand Down