What's the deal with the massive duplication in std.meta?

[Imperatorn]

On Friday, 30 April 2021 at 22:03:41 UTC, Andrei Alexandrescu 
wrote:
> cc Walter, Atila
>
> Phobos is like a toddler: you turn away for a few moments, and 
> then back and something really odd has happened.
>
> [...]

Ouch, didn't know about that..

A question though:
When we have fixed this, how do we make sure it doesn't keep 
happening?

I'm guessing more code review, but that's after the problem has 
already materialized.

Maybe better coding guidelines? Written by the high priest of D.

I would be very happy if we could produce some, and I would 
gladly read and follow them.