**Source Generator - Zero Boilerplate**

// Your service returns Result<T>
public async Task<Result<User>> GetUserAsync(int id)
{
    return await Result<int>.Ok(id)
        .Ensure(i => i > 0, "Invalid user ID")
        .BindAsync(async i => await _repository.FindAsync(i))
        .Ensure(u => u != null, new NotFoundError("User", id));
}

// Your controller just returns the Result - auto-converted!
app.MapGet("/users/{id}", async (int id) =>
    await _userService.GetUserAsync(id));

// 🆕 v1.10.0: OneOf extensions also work!
public OneOf<ValidationError, NotFoundError, User> GetOneOfUser(int id) { /* logic */ }

app.MapGet("/users/oneof/{id}", async (int id) =>
    GetOneOfUser(id)); // Auto-converts OneOf too!

// HTTP responses are automatically generated:
// 200 OK with User data
// 404 Not Found with ProblemDetails
// 400 Bad Request with validation errors