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Source: AL0043TrimSafeViolationAnalyzer.cs

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Description

Code marked with [TrimSafe] guarantees it will work correctly in trimmed applications. Calling methods with [RequiresUnreferencedCode] violates this guarantee because those methods may fail at runtime when types are trimmed.

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Bad Code

[TrimSafe]
public void ProcessData(object data) {
    // Warning: violates trim safety
    var json = JsonSerializer.Serialize(data);  // Uses reflection
}

[TrimSafe]
public T CreateInstance<T>() where T : new() {
    // Warning: Activator.CreateInstance uses reflection
    return Activator.CreateInstance<T>();
}

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Good Code

[TrimSafe]
public void ProcessData<T>(T data) {
    // Use source-generated serializer
    var json = JsonSerializer.Serialize(data, MyJsonContext.Default.GetTypeInfo<T>());
}

[TrimSafe]
public T CreateInstance<T>() where T : new() {
    // Direct constructor call - trim safe
    return new T();
}

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Properties

  • Category: Reliability
  • Severity: Warning
  • Enabled by default: True
  • Code fix available: False

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Configuration

dotnet_diagnostic.AL0043.severity = warning

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Notes

  • Trimming removes unused code to reduce binary size
  • Reflection-based code may fail when referenced types are trimmed
  • Use source generators instead of reflection for trim-safe code