Which language constructs could be done as a library if we accept some breaking changes?

[Elronnd]

On Sunday, 28 November 2021 at 20:47:28 UTC, Ola Fosheim Grøstad 
wrote:
> Which features that are currently in the language could with 
> some adjustments be done as a library feature?
>
> Class?

Classes should be a language feature in any case, for performance 
reasons