`@safe` by default. What about `@pure` and `immutable` by default?

[Adam D. Ruppe]

On Tuesday, 16 April 2019 at 03:59:38 UTC, Mike Franklin wrote:
> `@safe` by default is a no-brainer in my opinion, but `pure` 
> and `immutable` by default are less obvious.

I think pure should be too (and actually, even nothrow maybe), 
but not immutable.

With pure, you won't even actually notice it with the majority of 
functions... and if you do notice it, you can mostly just change 
a global to a function argument and solve it, which tends to be 
cleaner design anyway.

Though, one surprising problem with pure is that floating point 
functions don't count! We need to think up some solution to that.


immutable though is really a completely different paradigm. It is 
very invasive, there's no escape hatch (like with nothrow, you 
can put try/catch on to limit its influence, immutable has no way 
to get out), and I'd be surprised if any existing D code would 
work with that change; you'd definitely notice it.

We brag about having pure and mutable together, I like having 
that.