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Handle error case: static ref field (No NullReferenceException) #78707

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Merged
RikkiGibson merged 1 commit into from
May 23, 2025
Merged

Handle error case: static ref field (No NullReferenceException) #78707

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12 changes: 10 additions & 2 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 @@ -1389,7 +1389,6 @@ private bool CheckFieldValueKind(SyntaxNode node, BoundFieldAccess fieldAccess,

if (RequiresRefAssignableVariable(valueKind))
{
Debug.Assert(!fieldSymbol.IsStatic);
Debug.Assert(valueKind == BindValueKind.RefAssignable);

switch (fieldSymbol.RefKind)
Expand All @@ -1399,7 +1398,16 @@ private bool CheckFieldValueKind(SyntaxNode node, BoundFieldAccess fieldAccess,
return false;
case RefKind.Ref:
case RefKind.RefReadOnly:
return CheckIsValidReceiverForVariable(node, fieldAccess.ReceiverOpt, BindValueKind.Assignable, diagnostics);
if (fieldSymbol.IsStatic)
{
Debug.Assert(fieldAccess.ReceiverOpt is null or BoundTypeExpression);
break;
}
else
{
Debug.Assert(fieldAccess.ReceiverOpt is not null);
return CheckIsValidReceiverForVariable(node, fieldAccess.ReceiverOpt, BindValueKind.Assignable, diagnostics);
}
default:
throw ExceptionUtilities.UnexpectedValue(fieldSymbol.RefKind);
}
Expand Down
62 changes: 62 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/RefFieldTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -372,6 +372,32 @@ .field public int32& F2
CompileAndVerify(comp, verify: Verification.Skipped);
}

[WorkItem(78700, "https://github.com/dotnet/roslyn/issues/78700")]
[Fact]
public void StaticRefFieldInClass()
{
var code = """
class Program
{
static int g_3 = -6;
static int g_4 = 123;
static ref int g_2 = ref g_3;

static void Main(){
g_2 = ref g_4;
}
}
""";
var comp = CreateCompilation(code, references: [], parseOptions: TestOptions.Regular13, targetFramework: TargetFramework.Net70);
comp.VerifyEmitDiagnostics(
// (5,20): error CS0106: The modifier 'static' is not valid for this item
// static ref int g_2 = ref g_3;
Diagnostic(ErrorCode.ERR_BadMemberFlag, "g_2").WithArguments("static").WithLocation(5, 20),
// (5,20): error CS9059: A ref field can only be declared in a ref struct.
// static ref int g_2 = ref g_3;
Diagnostic(ErrorCode.ERR_RefFieldInNonRefStruct, "g_2").WithLocation(5, 20));
}

[Fact]
public void RefAndReadonlyRefStruct_01()
{
Expand Down Expand Up @@ -2069,6 +2095,42 @@ public void NonRefStructContainer(string type)
Diagnostic(ErrorCode.ERR_RefFieldInNonRefStruct, "F").WithLocation(4, 13));
}

[Theory]
[InlineData("class")]
[InlineData("struct")]
[InlineData("record")]
[InlineData("record struct")]
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@RikkiGibson RikkiGibson May 23, 2025 •
edited
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Do we also have a test for static ref int F; in ref struct?

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@RikkiGibson RikkiGibson May 23, 2025

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Looks like this one covers it:

https://github.com/dotnet/roslyn/blob/4a39725ac8b891eabd27585df9cebe4d97f9970f/src/Compilers/CSharp/Test/Semantic/Semantics/RefFieldTests.cs#L669

public void NonRefStructContainerWithStaticRefField(string type)
{
var source =
$@"#pragma warning disable 169
{type} R
{{
static ref int F;
}}";

var comp = CreateCompilation(source, parseOptions: TestOptions.Regular10, targetFramework: TargetFramework.Net70);
comp.VerifyEmitDiagnostics(
// (4,12): error CS8936: Feature 'ref fields' is not available in C# 10.0. Please use language version 11.0 or greater.
// static ref int F;
Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion10, "ref int").WithArguments("ref fields", "11.0").WithLocation(4, 12),
// (4,20): error CS0106: The modifier 'static' is not valid for this item
// static ref int F;
Diagnostic(ErrorCode.ERR_BadMemberFlag, "F").WithArguments("static").WithLocation(4, 20),
// (4,20): error CS9059: A ref field can only be declared in a ref struct.
// static ref int F;
Diagnostic(ErrorCode.ERR_RefFieldInNonRefStruct, "F").WithLocation(4, 20));

comp = CreateCompilation(source, targetFramework: TargetFramework.Net70);
comp.VerifyEmitDiagnostics(
// (4,20): error CS0106: The modifier 'static' is not valid for this item
// static ref int F;
Diagnostic(ErrorCode.ERR_BadMemberFlag, "F").WithArguments("static").WithLocation(4, 20),
// (4,20): error CS9059: A ref field can only be declared in a ref struct.
// static ref int F;
Diagnostic(ErrorCode.ERR_RefFieldInNonRefStruct, "F").WithLocation(4, 20));
}

/// <summary>
/// Determination of enum underlying type should ignore ref fields
/// and fields with required custom modifiers.
Expand Down