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Let tuple/anonymous member name inference see through null suppression operator #80908

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Let tuple/anonymous member name inference see through null suppression operator #80908

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c268e35
Let tuple/anonymous member name inference see through null suppressio…
DoctorKrolic Oct 26, 2025
a00ccb2
Fix tests
DoctorKrolic Oct 26, 2025
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4 changes: 4 additions & 0 deletions src/Compilers/CSharp/Portable/Syntax/SyntaxNodeExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,10 @@ internal static SyntaxToken ExtractAnonymousTypeMemberName(this ExpressionSyntax

continue;

case SyntaxKind.SuppressNullableWarningExpression:
input = ((PostfixUnaryExpressionSyntax)input).Operand;
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@AlekseyTs AlekseyTs Oct 27, 2025

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input = ((PostfixUnaryExpressionSyntax)input).Operand;

It looks like this potentially can introduce a breaking change for an existing code. Let's add test(s) demonstrating that. And also let's document the breaking change. Once that is done, we can start an internal process for approving the breaking change.

continue;

default:
return default(SyntaxToken);
}
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6 changes: 3 additions & 3 deletions src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs
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Expand Up @@ -80646,9 +80646,9 @@ void M(C<string?> c)
Diagnostic(ErrorCode.WRN_NullReferenceReceiver, "t4.Item1").WithLocation(25, 9),

// line 6
// (34,52): warning CS8619: Nullability of reference types in value of type '(C<string?>, string)' doesn't match target type '(C<string>, string)'.
// (34,52): warning CS8619: Nullability of reference types in value of type '(C<string?> c, string)' doesn't match target type '(C<string>, string)'.
// (string, (C<string>, string)) t6 = (null!, (c!, null!)); // warn
Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "(c!, null!)").WithArguments("(C<string?>, string)", "(C<string>, string)").WithLocation(34, 52),
Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "(c!, null!)").WithArguments("(C<string?> c, string)", "(C<string>, string)").WithLocation(34, 52),

// line 8
// (44,51): warning CS8619: Nullability of reference types in value of type '(C<string?> c, string?)' doesn't match target type '(C<string>, string)'.
Expand Down Expand Up @@ -85853,7 +85853,7 @@ static void F(string? x, string? y)
{
(object a, long b) t = (x, 0)/*T:(string? x, int)*/; // 1
(object a, (long b, object c)) t2 = (x, (0, y)/*T:(int, string? y)*/)/*T:(string? x, (int, string? y))*/; // 2, 3
(object a, (long b, object c)) t3 = (x!, (0, y!)/*T:(int, string!)*/)/*T:(string!, (int, string!))*/;
(object a, (long b, object c)) t3 = (x!, (0, y!)/*T:(int, string! y)*/)/*T:(string! x, (int, string! y))*/;
(int b, string? c)? t4 = null;
(object? a, (long b, object? c)?) t5 = (x, t4)/*T:(string? x, (int b, string? c)? t4)*/;

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62 changes: 62 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/ValueTupleTests.cs
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Expand Up @@ -843,5 +843,67 @@ void M()
Assert.Equal("C", secondTupleArgInfo.Type.ToTestDisplayString());
Assert.Equal("C", secondTupleArgInfo.ConvertedType.ToTestDisplayString());
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/80752")]
public void ElementNameInference_FromLocal_NullSuppression()
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@AlekseyTs AlekseyTs Oct 27, 2025

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ElementNameInference_FromLocal_NullSuppression

It would be good to add a test with a motivating scenario for adding the suppression. I.e. a scenario that benefits from adding !.

{
var source = """
#nullable enable

class C
{
string M()
{
string? str = null;
C? c = null;
var t = (str!, c!);
return t.str ?? "";
}
}
""";

var comp = CreateCompilation(source);
comp.VerifyDiagnostics();

var tree = comp.SyntaxTrees.First();
var model = comp.GetSemanticModel(tree);

var tupleExpression = tree.GetCompilationUnitRoot().DescendantNodes().OfType<TupleExpressionSyntax>().Single();
var tupleTypeInfo = model.GetTypeInfo(tupleExpression);
Assert.Equal("(System.String str, C c)", tupleTypeInfo.Type.ToTestDisplayString());
Assert.Equal("(System.String str, C c)", tupleTypeInfo.ConvertedType.ToTestDisplayString());
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/80752")]
public void ElementNameInference_FromPropertyName_NullSuppression()
{
var source = """
#nullable enable

class C
{
public string? Prop1 { get; set; }

public string? Prop2 { get; set; }

string M(C c)
{
var t = (c.Prop1!, c.Prop2!);
return t.Prop1 ?? "";
}
}
""";

var comp = CreateCompilation(source);
comp.VerifyDiagnostics();

var tree = comp.SyntaxTrees.First();
var model = comp.GetSemanticModel(tree);

var tupleExpression = tree.GetCompilationUnitRoot().DescendantNodes().OfType<TupleExpressionSyntax>().Single();
var tupleTypeInfo = model.GetTypeInfo(tupleExpression);
Assert.Equal("(System.String Prop1, System.String Prop2)", tupleTypeInfo.Type.ToTestDisplayString());
Assert.Equal("(System.String Prop1, System.String Prop2)", tupleTypeInfo.ConvertedType.ToTestDisplayString());
}
}
}
74 changes: 74 additions & 0 deletions src/Compilers/CSharp/Test/Symbol/Symbols/AnonymousTypesSymbolTests.cs
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Expand Up @@ -1927,5 +1927,79 @@ .maxstack 2

this.CompileAndVerify(compilation).VerifyIL("C.Main", expectedIL);
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/80752")]
public void ElementNameInference_FromLocal_NullSuppression()
{
var source = """
#nullable enable

class C
{
string M()
{
string? str = null;
C? c = null;
var a = new { str!, c! };
return a.str ?? "";
}
}
""";

var comp = CreateCompilation(source);
comp.VerifyDiagnostics(
// (9,23): error CS0746: Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access.
// var a = new { str!, c! };
Diagnostic(ErrorCode.ERR_InvalidAnonymousTypeMemberDeclarator, "str!").WithLocation(9, 23),
// (9,29): error CS0746: Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access.
// var a = new { str!, c! };
Diagnostic(ErrorCode.ERR_InvalidAnonymousTypeMemberDeclarator, "c!").WithLocation(9, 29));

var tree = comp.SyntaxTrees.First();
var model = comp.GetSemanticModel(tree);

var tupleExpression = tree.GetCompilationUnitRoot().DescendantNodes().OfType<AnonymousObjectCreationExpressionSyntax>().Single();
var tupleTypeInfo = model.GetTypeInfo(tupleExpression);
Assert.Equal("<anonymous type: System.String str, C c>", tupleTypeInfo.Type.ToTestDisplayString());
Assert.Equal("<anonymous type: System.String str, C c>", tupleTypeInfo.ConvertedType.ToTestDisplayString());
}

[Fact, WorkItem("https://github.com/dotnet/roslyn/issues/80752")]
public void ElementNameInference_FromPropertyName_NullSuppression()
{
var source = """
#nullable enable

class C
{
public string? Prop1 { get; set; }

public string? Prop2 { get; set; }

string M(C c)
{
var a = new { c.Prop1!, c.Prop2! };
return a.Prop1 ?? "";
}
}
""";

var comp = CreateCompilation(source);
comp.VerifyDiagnostics(
// (11,23): error CS0746: Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access.
// var a = new { c.Prop1!, c.Prop2! };
Diagnostic(ErrorCode.ERR_InvalidAnonymousTypeMemberDeclarator, "c.Prop1!").WithLocation(11, 23),
// (11,33): error CS0746: Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access.
// var a = new { c.Prop1!, c.Prop2! };
Diagnostic(ErrorCode.ERR_InvalidAnonymousTypeMemberDeclarator, "c.Prop2!").WithLocation(11, 33));

var tree = comp.SyntaxTrees.First();
var model = comp.GetSemanticModel(tree);

var tupleExpression = tree.GetCompilationUnitRoot().DescendantNodes().OfType<AnonymousObjectCreationExpressionSyntax>().Single();
var tupleTypeInfo = model.GetTypeInfo(tupleExpression);
Assert.Equal("<anonymous type: System.String Prop1, System.String Prop2>", tupleTypeInfo.Type.ToTestDisplayString());
Assert.Equal("<anonymous type: System.String Prop1, System.String Prop2>", tupleTypeInfo.ConvertedType.ToTestDisplayString());
}
}
}