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Detect struct cycles caused by erroneous field-like event declarations #75668

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merged 1 commit into from
Oct 30, 2024
Merged

Detect struct cycles caused by erroneous field-like event declarations #75668

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37 changes: 31 additions & 6 deletions src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2380,13 +2380,23 @@ private bool HasStructCircularity(BindingDiagnosticBag diagnostics)
{
foreach (var member in valuesByName)
{
if (member.Kind != SymbolKind.Field)
FieldSymbol? field;

// Only instance fields (including field-like events) affect the outcome.
switch (member.Kind)
{
// NOTE: don't have to check field-like events, because they can't have struct types.
continue;
case SymbolKind.Field:
field = (FieldSymbol)member;
Debug.Assert(field.AssociatedSymbol is not EventSymbol, "Didn't expect to find a field-like event backing field in the member list.");
break;
case SymbolKind.Event:
field = ((EventSymbol)member).AssociatedField;
break;
default:
continue;
}
var field = (FieldSymbol)member;
if (field.IsStatic)

if (field is null || field.IsStatic)
{
continue;
}
Expand Down Expand Up @@ -2670,7 +2680,22 @@ private void CheckFiniteFlatteningGraph(BindingDiagnosticBag diagnostics)
instanceMap.Add(this, this);
foreach (var m in this.GetMembersUnordered())
{
var f = m as FieldSymbol;
FieldSymbol? f;

// Only instance fields (including field-like events) affect the outcome.
switch (m.Kind)
{
case SymbolKind.Field:
f = (FieldSymbol)m;
Debug.Assert(f.AssociatedSymbol is not EventSymbol, "Didn't expect to find a field-like event backing field in the member list.");
break;
case SymbolKind.Event:
f = ((EventSymbol)m).AssociatedField;
break;
default:
continue;
}

if (f is null || !f.IsStatic || f.Type.TypeKind != TypeKind.Struct) continue;
var type = (NamedTypeSymbol)f.Type;
if (InfiniteFlatteningGraph(this, type, instanceMap))
Expand Down
13 changes: 12 additions & 1 deletion src/Compilers/CSharp/Test/Emit3/FlowAnalysis/FlowDiagnosticTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -964,6 +964,11 @@ struct D<T>
{
static C<D<T>> x;
}
#pragma warning disable CS0067 // The event 'E<T>.x' is never used
struct E<T>
{
static event E<E<T>> x;
}
";
CreateCompilation(program)
.VerifyDiagnostics(
Expand All @@ -987,7 +992,13 @@ struct D<T>
Diagnostic(ErrorCode.WRN_UnreferencedField, "x").WithArguments("D<T>.x").WithLocation(18, 20),
// (14,17): warning CS0169: The field 'C<T>.x' is never used
// static D<T> x;
Diagnostic(ErrorCode.WRN_UnreferencedField, "x").WithArguments("C<T>.x").WithLocation(14, 17)
Diagnostic(ErrorCode.WRN_UnreferencedField, "x").WithArguments("C<T>.x").WithLocation(14, 17),
// (23,26): error CS0523: Struct member 'E<T>.x' of type 'E<E<T>>' causes a cycle in the struct layout
// static event E<E<T>> x;
Diagnostic(ErrorCode.ERR_StructLayoutCycle, "x").WithArguments("E<T>.x", "E<E<T>>").WithLocation(23, 26),
// (23,26): error CS0066: 'E<T>.x': event must be of a delegate type
// static event E<E<T>> x;
Diagnostic(ErrorCode.ERR_EventNotDelegate, "x").WithArguments("E<T>.x").WithLocation(23, 26)
);
}

Expand Down
24 changes: 14 additions & 10 deletions src/Compilers/CSharp/Test/Semantic/Semantics/GenericConstraintsTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3773,7 +3773,7 @@ public struct YourStruct<T> where T : unmanaged
Assert.False(compilation.GetMember<NamedTypeSymbol>("YourStruct").IsManagedTypeNoUseSiteDiagnostics);
}

[Fact(Skip = "https://github.com/dotnet/roslyn/issues/75620")]
[Fact]
[WorkItem("https://github.com/dotnet/roslyn/issues/75620")]
public void UnmanagedExpandingTypeArgumentConstraintViolation_05()
{
Expand All @@ -3794,6 +3794,9 @@ public struct YourStruct<T> where T : unmanaged
var compilation = CreateCompilation(code, options: TestOptions.UnsafeReleaseDll);

compilation.VerifyDiagnostics(
// (6,52): error CS0523: Struct member 'MyStruct<T>.field' of type 'YourStruct<MyStruct<MyStruct<T>>>' causes a cycle in the struct layout
// public event YourStruct<MyStruct<MyStruct<T>>> field;
Diagnostic(ErrorCode.ERR_StructLayoutCycle, "field").WithArguments("MyStruct<T>.field", "YourStruct<MyStruct<MyStruct<T>>>").WithLocation(6, 52),
// (6,52): error CS0066: 'MyStruct<T>.field': event must be of a delegate type
// public event YourStruct<MyStruct<MyStruct<T>>> field;
Diagnostic(ErrorCode.ERR_EventNotDelegate, "field").WithArguments("MyStruct<T>.field").WithLocation(6, 52),
Expand All @@ -3806,7 +3809,7 @@ public struct YourStruct<T> where T : unmanaged
Assert.False(compilation.GetMember<NamedTypeSymbol>("YourStruct").IsManagedTypeNoUseSiteDiagnostics);
}

[Fact(Skip = "https://github.com/dotnet/roslyn/issues/75620")]
[Fact]
[WorkItem("https://github.com/dotnet/roslyn/issues/75620")]
public void UnmanagedExpandingTypeArgumentConstraintViolation_06()
{
Expand All @@ -3826,15 +3829,16 @@ public struct YourStruct<T> where T : unmanaged
";
var compilation = CreateCompilation(code, options: TestOptions.UnsafeReleaseDll);
compilation.VerifyDiagnostics(
// (4,52): error CS0066: 'MyStruct<T>.field': event must be of a delegate type
// (7,52): error CS0523: Struct member 'MyStruct<T>.field' of type 'YourStruct<MyStruct<MyStruct<T>>>' causes a cycle in the struct layout
// public event YourStruct<MyStruct<MyStruct<T>>> field;
Diagnostic(ErrorCode.ERR_EventNotDelegate, "field").WithArguments("MyStruct<T>.field").WithLocation(4, 52),
// (5,46): error CS0523: Struct member 'MyStruct<T>.field' of type 'YourStruct<MyStruct<MyStruct<T>>>' causes a cycle in the struct layout
// public YourStruct<MyStruct<MyStruct<T>>> field;
Diagnostic(ErrorCode.ERR_StructLayoutCycle, "field").WithArguments("MyStruct<T>.field", "YourStruct<MyStruct<MyStruct<T>>>").WithLocation(5, 46),
// (5,46): error CS8377: The type 'MyStruct<MyStruct<T>>' must be a non-nullable value type, along with all fields at any level of nesting, in order to use it as parameter 'T' in the generic type or method 'YourStruct<T>'
// public YourStruct<MyStruct<MyStruct<T>>> field;
Diagnostic(ErrorCode.ERR_UnmanagedConstraintNotSatisfied, "field").WithArguments("YourStruct<T>", "T", "MyStruct<MyStruct<T>>").WithLocation(5, 46));
Diagnostic(ErrorCode.ERR_StructLayoutCycle, "field").WithArguments("MyStruct<T>.field", "YourStruct<MyStruct<MyStruct<T>>>").WithLocation(7, 52),
// (7,52): error CS0066: 'MyStruct<T>.field': event must be of a delegate type
// public event YourStruct<MyStruct<MyStruct<T>>> field;
Diagnostic(ErrorCode.ERR_EventNotDelegate, "field").WithArguments("MyStruct<T>.field").WithLocation(7, 52),
// (7,52): error CS8377: The type 'MyStruct<MyStruct<T>>' must be a non-nullable value type, along with all fields at any level of nesting, in order to use it as parameter 'T' in the generic type or method 'YourStruct<T>'
// public event YourStruct<MyStruct<MyStruct<T>>> field;
Diagnostic(ErrorCode.ERR_UnmanagedConstraintNotSatisfied, "field").WithArguments("YourStruct<T>", "T", "MyStruct<MyStruct<T>>").WithLocation(7, 52)
);

Assert.True(compilation.GetMember<NamedTypeSymbol>("MyStruct").IsManagedTypeNoUseSiteDiagnostics);
Assert.False(compilation.GetMember<NamedTypeSymbol>("YourStruct").IsManagedTypeNoUseSiteDiagnostics);
Expand Down