> ## Documentation Index
> Fetch the complete documentation index at: https://ancplua.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# AL0103 - Closed type hierarchy switch exhaustiveness

> Switch on sealed hierarchy should cover all cases

Source: [Al0103ClosedTypeHierarchySwitchAnalyzer.cs](https://github.com/ANcpLua/ANcpLua.Analyzers/blob/main/src/ANcpLua.Analyzers/Analyzers/Al0103ClosedTypeHierarchySwitchAnalyzer.cs)

## Description

When switching over a sealed type hierarchy (abstract class or interface with all implementations in the same assembly), the switch should cover all derived types to catch missing cases at compile time.

## Bad Code

```csharp theme={null}
public abstract record Shape;
public record Circle : Shape;
public record Square : Shape;

string Describe(Shape s) => s switch
{
    Circle c => "circle",
    _ => "unknown" // Misses Square
};
```

## Good Code

```csharp theme={null}
string Describe(Shape s) => s switch
{
    Circle c => "circle",
    Square sq => "square",
    _ => throw new UnreachableException()
};
```

## Properties

* **Category**: Design
* **Severity**: Warning
* **Enabled by default**: True
* **Code fix available**: True

## Configuration

```editorconfig theme={null}
dotnet_diagnostic.AL0103.severity = warning
```