Command–query separation principle [re: @mustuse as a function attribute]

[Adam D Ruppe]

On Wednesday, 19 October 2022 at 18:50:41 UTC, Paul Backus wrote:
> Another way to think of it is: @safe is like an "out" contract, 
> and @mustuse is like an "in" contract.

ok yeah, that's exactly what i had in mind, i was just in a rush 
(made it to my meeting with 20s to spare! lol). I think this 
makes sense and is a useful framework for answering all the other 
questions.