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Fix type parameter scoping for local functions #59968

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Fix type parameter scoping for local functions #59968

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8576ad6
Fix type parameter scoping for local functions
Youssef1313 Mar 5, 2022
bb9ed8e
Fix LookupPosition test
Youssef1313 Mar 5, 2022
218dcaf
Use ParameterBinder
Youssef1313 Mar 5, 2022
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2 changes: 1 addition & 1 deletion src/Compilers/CSharp/Portable/Compilation/MemberSemanticModel.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -358,7 +358,7 @@ private static Binder GetEnclosingBinderInternalWithinRoot(SyntaxNode node, int
LocalFunctionSymbol function = GetDeclaredLocalFunction(binder, ownerOfTypeParametersInScope.Identifier);
if ((object)function != null)
{
binder = function.SignatureBinder;
binder = function.ParameterBinder;
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SignatureBinder is used for attribute binding, hence, it doesn't have type parameters in scope. This code path used by LookupPosition wants to have type parameters in scope, so I switched to using ParameterBinder here.

}
}

Expand Down
13 changes: 7 additions & 6 deletions src/Compilers/CSharp/Portable/Symbols/Source/LocalFunctionSymbol.cs
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Expand Up @@ -15,6 +15,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Symbols
internal sealed class LocalFunctionSymbol : SourceMethodSymbolWithAttributes
{
private readonly Binder _binder;
private readonly Binder? _withTypeParamsBinder;
private readonly Symbol _containingSymbol;
private readonly DeclarationModifiers _declarationModifiers;
private readonly ImmutableArray<SourceMethodTypeParameterSymbol> _typeParameters;
Expand Down Expand Up @@ -60,7 +61,7 @@ internal sealed class LocalFunctionSymbol : SourceMethodSymbolWithAttributes

if (syntax.TypeParameterList != null)
{
binder = new WithMethodTypeParametersBinder(this, binder);
_withTypeParamsBinder = new WithMethodTypeParametersBinder(this, binder);
_typeParameters = MakeTypeParameters(_declarationDiagnostics);
}
else
Expand Down Expand Up @@ -105,7 +106,7 @@ internal sealed class LocalFunctionSymbol : SourceMethodSymbolWithAttributes
/// </summary>
internal Binder ScopeBinder { get; }

internal override Binder ParameterBinder => _binder;
internal override Binder ParameterBinder => _withTypeParamsBinder ?? _binder;

internal LocalFunctionStatementSyntax Syntax => (LocalFunctionStatementSyntax)syntaxReferenceOpt.GetSyntax();

Expand Down Expand Up @@ -180,7 +181,7 @@ private void ComputeParameters()
var diagnostics = BindingDiagnosticBag.GetInstance(_declarationDiagnostics);

var parameters = ParameterHelpers.MakeParameters(
_binder,
_withTypeParamsBinder ?? _binder,
this,
this.Syntax.ParameterList,
arglistToken: out arglistToken,
Expand Down Expand Up @@ -239,7 +240,7 @@ internal void ComputeReturnType()

var diagnostics = BindingDiagnosticBag.GetInstance(_declarationDiagnostics);
TypeSyntax returnTypeSyntax = Syntax.ReturnType;
TypeWithAnnotations returnType = _binder.BindType(returnTypeSyntax.SkipRef(), diagnostics);
TypeWithAnnotations returnType = (_withTypeParamsBinder ?? _binder).BindType(returnTypeSyntax.SkipRef(), diagnostics);

var compilation = DeclaringCompilation;

Expand Down Expand Up @@ -476,7 +477,7 @@ public override ImmutableArray<ImmutableArray<TypeWithAnnotations>> GetTypeParam
var syntax = Syntax;
var diagnostics = BindingDiagnosticBag.GetInstance(_declarationDiagnostics);
var constraints = this.MakeTypeParameterConstraintTypes(
_binder,
_withTypeParamsBinder ?? _binder,
TypeParameters,
syntax.TypeParameterList,
syntax.ConstraintClauses,
Expand All @@ -501,7 +502,7 @@ public override ImmutableArray<TypeParameterConstraintKind> GetTypeParameterCons
{
var syntax = Syntax;
var constraints = this.MakeTypeParameterConstraintKinds(
_binder,
_withTypeParamsBinder ?? _binder,
TypeParameters,
syntax.TypeParameterList,
syntax.ConstraintClauses);
Expand Down
33 changes: 33 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/LocalFunctionTests.cs
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Expand Up @@ -7117,5 +7117,38 @@ async void F4()
// async static void B4<await>() { }
Diagnostic(ErrorCode.WRN_LowerCaseTypeName, "await").WithArguments("await").WithLocation(23, 30));
}

[Fact]
public void TypeParameterScope()
{
var comp = CreateCompilation(@"
class C
{
void M()
{
local<object>();

[My(nameof(TParameter))] // works, but why?
void local<TParameter>() { }
}

[My(nameof(TParameter))] // error CS0103: The name 'TParameter' does not exist in the current context
void M2<TParameter>() { }
}

public class MyAttribute : System.Attribute
{
public MyAttribute(string name1) { }
}
");
comp.VerifyDiagnostics(
// (8,20): error CS0103: The name 'TParameter' does not exist in the current context
// [My(nameof(TParameter))] // works, but why?
Diagnostic(ErrorCode.ERR_NameNotInContext, "TParameter").WithArguments("TParameter").WithLocation(8, 20),
// (12,16): error CS0103: The name 'TParameter' does not exist in the current context
// [My(nameof(TParameter))] // error CS0103: The name 'TParameter' does not exist in the current context
Diagnostic(ErrorCode.ERR_NameNotInContext, "TParameter").WithArguments("TParameter").WithLocation(12, 16)
);
}
}
}