AL0043 - TrimSafe violation

[TrimSafe] code must not call methods with [RequiresUnreferencedCode]

Source: AL0043TrimSafeViolationAnalyzer.cs

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.

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>();
}

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();
}

Properties

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

Configuration

dotnet_diagnostic.AL0043.severity = warning

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