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Extensions: fix issue with GetParameterOrExtensionParameter #79402

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Merged
merged 4 commits into from
Jul 21, 2025
Merged

Extensions: fix issue with GetParameterOrExtensionParameter #79402

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3863d2e
Extensions: fix issue with GetParameterOrExtensionParameter
Jul 11, 2025
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Address feedback
Jul 18, 2025
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Jul 18, 2025
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Merge remote-tracking branch 'dotnet/main' into extensions-getparameter
Jul 21, 2025
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6 changes: 3 additions & 3 deletions src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2091,19 +2091,19 @@ private void RemoveWorseMembers<TMember>(ArrayBuilder<MemberResolutionResult<TMe
private static ParameterSymbol GetParameterOrExtensionParameter<TMember>(int argIndex, MemberAnalysisResult result, ImmutableArray<ParameterSymbol> parameters, TMember member)
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@AlekseyTs AlekseyTs Jul 18, 2025 •
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GetParameterOrExtensionParameter

Let's make this a local function in BetterFunctionMember. It looks like it is used only in that function, and that function is a source of mismatch between parameters and arguments,

where TMember : Symbol
{
int paramIndex = result.ParameterFromArgument(argIndex);
if (member.GetIsNewExtensionMember())
{
if (argIndex == 0)
if (paramIndex == 0)
{
ParameterSymbol? extensionParameter = member.ContainingType.ExtensionParameter;
Debug.Assert(extensionParameter is not null);
return extensionParameter;
}

argIndex--;
paramIndex--;
}

int paramIndex = result.ParameterFromArgument(argIndex);
return parameters[paramIndex];
}

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206 changes: 206 additions & 0 deletions src/Compilers/CSharp/Test/Emit3/Semantics/ExtensionTests2.cs
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Expand Up @@ -14361,5 +14361,211 @@ public static class E
var extension = (SourceNamedTypeSymbol)comp.GetMember<NamedTypeSymbol>("E").GetTypeMembers().Single();
AssertEx.Equal("extension([MyAttribute/*()*/] System.Int32)", extension.ComputeExtensionMarkerRawName());
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_01()
{
var src = """
public static class E
{
extension(object @this)
{
public void M<T>(T x)
{
@this.M(x, default);
}

public void M(params System.ReadOnlySpan<object> span)
{
}

private void M<T>(T x, System.ReadOnlySpan<object> span)
{
}
}
}
""";
var comp = CreateCompilation(src, targetFramework: TargetFramework.Net90);
comp.VerifyEmitDiagnostics();
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@AlekseyTs AlekseyTs Jul 18, 2025 •
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comp.VerifyEmitDiagnostics();

Let's execute and observe result. #Closed

}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_02()
{
var src = """
new object().M(a: null);

public static class E
{
extension(object o1)
{
public void M(object a) { }

public void M(string a) { System.Console.Write("ran"); }
}
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_03()
{
var src = """
new object().M(a: null);

public static class E
{
extension(object o1)
{
public void M(object a) { }
}

public static void M(this object o, string a) { System.Console.Write("ran"); }
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_04()
{
var src = """
new object().M(a: null);

public static class E
{
extension(object o1)
{
public void M(string a) { System.Console.Write("ran"); }
}

public static void M(this object o, object a) { }
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_05()
{
var src = """
new object().M(a: null);

public static class E
{
extension(object o1)
{
public void M(object a) { }
public void M(params int[] a) { System.Console.Write("ran"); }
}
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_06()
{
var src = """
new object().M(1, 2);

public static class E
{
extension(object o1)
{
public void M(int x1, int x2) { System.Console.Write("ran"); }
public void M(params int[] a) { }
}
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_07()
{
var src = """
new object().M(a: 1, 2);

public static class E
{
extension(object o1)
{
public void M(int a, int b) { System.Console.Write("ran"); }
public void M(params int[] a) { }
}
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_08()
{
var src = """
new object().M(index: 0, 1, 2);

public static class E
{
extension(object o1)
{
public void M(int index, int a, int b) { System.Console.Write("ran"); }
public void M(int index, params int[] a) { }
}
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_09()
{
var src = """
object.M(index: 0, 1, 2);

public static class E
{
extension(object)
{
public static void M(int index, int a, int b) { System.Console.Write("ran"); }
public static void M(int index, params int[] a) { }
}
}
""";
var comp = CreateCompilation(src);
CompileAndVerify(comp, expectedOutput: "ran").VerifyDiagnostics();
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/79193")]
public void OverloadResolution_10()
{
var src = """
1.M(2);

public static class E
{
extension(params int[] i)
{
public static void M() { }
}
}
""";
var comp = CreateCompilation(src);
comp.VerifyEmitDiagnostics(
// (5,15): error CS1670: params is not valid in this context
// extension(params int[] i)
Diagnostic(ErrorCode.ERR_IllegalParams, "params").WithLocation(5, 15),
// (1,3): error CS1501: No overload for method 'M' takes 1 arguments
// 1.M(2);
Diagnostic(ErrorCode.ERR_BadArgCount, "M").WithArguments("M", "1").WithLocation(1, 3));
}
}

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