The yield! keyword

[HeyAnon]

Hi guys, I'm tired of writing a boilerplate every day at work:

public class A
{
    public virtual IEnumerable<string> Test()
    {
        yield break;
    }
}

public class B : A
{
    public override IEnumerable<string> Test()
    {
        yield return "aaa";

        foreach (var baseElement in base.Test())
        {
            yield return baseElement;
        }

        yield return "ccc";
    }
}

I saw a great solution in the F#: https://docs.microsoft.com/ru-ru/dotnet/fsharp/language-reference/sequences#the-yield-keyword

Code

    public override IEnumerable<string> Test()
    {
        yield return "aaa";

        yield! return base.Test();

        yield return "ccc";
    }

much more compact and readable

[ufcpp]

#378

[theunrepentantgeek]

To summarise discussions elsewhere...

Introducing a keyword is believed to imply it's an O(1) operation when the only possible compiler implementation is O(n). This makes the feature extremely likely to conceal performance issues, creating a tiger-trap for future developers.

Writing the boilerplate might be tedious, but the LDM prefers it to the creation of dangers.

[NikitaEgorov]

F# already have this construction https://docs.microsoft.com/ru-ru/dotnet/fsharp/language-reference/sequences#the-yield-keyword