N.SourceGenerators.UnionTypes 0.2.0

N.SourceGenerators.UnionTypes

Discriminated union type source generator

Motivation

C# doesn't support discriminated unions yet. This source generator helps automate writing union types.

Using

Add package reference to N.SourceGenerators.UnionTypes

dotnet add package N.SourceGenerators.UnionTypes

Create a partial class that will be used as a union type

public partial class FooResult
{
}

Add types you want to use in a discriminated union

public record Success(int Value);
public record ValidationError(string Message);
public record NotFoundError;

public partial class FooResult
{
}

Add N.SourceGenerators.UnionTypes.UnionTypeAttribute to a union type.

using N.SourceGenerators.UnionTypes;

public record Success(int Value);
public record ValidationError(string Message);
public record NotFoundError;

[UnionType(typeof(Success))]
[UnionType(typeof(ValidationError))]
[UnionType(typeof(NotFoundError))]
public partial class FooResult
{
}

Examples

All examples can be found in examples project

Implicit conversion

public FooResult ImplicitReturn()
{
    // you can return any union type variant without creating FooResult
    return new NotFoundError();
}

Explicit conversion

public ValidationError ExplicitCast(FooResult result)
{
    return (ValidationError)result;
}