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Use IOperation to detect implicit integer-to-enum conversions #27

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Copilot Nov 22, 2025
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Use IOperation to detect both explicit and implicit integer-to-enum c…
Copilot Nov 22, 2025
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29 changes: 18 additions & 11 deletions src/StaticCs/EnumClosedConversionAnalyzer.cs
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Original file line number Diff line number Diff line change
@@ -1,9 +1,8 @@

using System.Collections.Immutable;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Operations;

namespace StaticCs;

Expand All @@ -24,22 +23,30 @@ public override void Initialize(AnalysisContext ctx)
{
ctx.EnableConcurrentExecution();
ctx.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.ReportDiagnostics);
ctx.RegisterSyntaxNodeAction(ctx =>
ctx.RegisterOperationAction(ctx =>
{
var castSyntax = (CastExpressionSyntax)ctx.Node;
var model = ctx.SemanticModel;
var targetTypeInfo = model.GetTypeInfo(castSyntax.Type);

if (targetTypeInfo.Type is { TypeKind: TypeKind.Enum } type)
var conversion = (IConversionOperation)ctx.Operation;

// Check if the conversion is from an integer type to an enum type
if (conversion.Type is { TypeKind: TypeKind.Enum } targetType &&
conversion.Operand.Type?.SpecialType is
SpecialType.System_SByte or
SpecialType.System_Byte or
SpecialType.System_Int16 or
SpecialType.System_UInt16 or
SpecialType.System_Int32 or
SpecialType.System_UInt32 or
SpecialType.System_Int64 or
SpecialType.System_UInt64)
{
foreach (var attr in type.GetAttributes())
foreach (var attr in targetType.GetAttributes())
{
if (attr.AttributeClass?.ToDisplayString() == "StaticCs.ClosedAttribute")
{
ctx.ReportDiagnostic(Diagnostic.Create(s_descriptor, castSyntax.GetLocation(), type));
ctx.ReportDiagnostic(Diagnostic.Create(s_descriptor, conversion.Syntax.GetLocation(), targetType));
}
}
}
}, SyntaxKind.CastExpression);
}, OperationKind.Conversion);
}
}
6 changes: 4 additions & 2 deletions test/test/ClosedTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,7 @@ await VerifyDiagnostics<EnumClosedConversionAnalyzer>(src,
}

[Fact]
public async Task ImplicitConversionToClosedLoophole()
public async Task ImplicitConversionToClosedError()
{
var src = """
using System;
Expand All @@ -96,7 +96,9 @@ void M()
}
}
""";
await VerifyDiagnostics<EnumClosedConversionAnalyzer>(src);
await VerifyDiagnostics<EnumClosedConversionAnalyzer>(src,
// /0/Test0.cs(9,19): error STATICCS002: Integer conversions to [Closed] enum Rgb are disallowed
ClosedEnumConversion.WithSpan(9, 19, 9, 20).WithArguments("Rgb"));
}

[Fact]
Expand Down