How can we make it easier to experiment with the compiler

[Ola Fosheim Grøstad]

On Tuesday, 25 May 2021 at 13:11:17 UTC, Ola Fosheim Grøstad 
wrote:
> 1. Write new AST and translation to old AST. Not disruptive.
>
> 2. Write translation from old AST to new IR, and encourge 
> backends to transition. Not disruptive.
>
> 3. Transition to new IR, by making old AST private. Backends 
> are ready. Not disruptive.
>
> 4. Move passes one by one to new IR. Not disruptive.
>
> 5. Write translation from new AST to new IR. Done.

If you are unsure if the new IR is stable you can rearrange the 
sequence like this instead:

new AST -> new IR -> old AST

Perhaps better as it gives more time for backends to transition.