Store mutable indirections in immutable data with this one weird trick!

[tsbockman]

On Saturday, 13 November 2021 at 08:32:42 UTC, Timon Gehr wrote:
> On 13.11.21 09:30, tsbockman wrote:
>>>
>> 
>> That's a compiler bug.
>
> Nonsense. Results of strongly pure function calls implicitly 
> convert to immutable. Your "fix" just avoided purity inference.

I see. This does not appear to be documented anywhere in the spec 
at the moment.

I found definitions for "strongly pure" and "pure factory 
function", but nothing about exceptions to the normal implicit 
conversion rules. After being defined, the latter term is never 
used again in the spec.

There is also no mention of this in the "Creating Immutable Data" 
section:
     https://dlang.org/spec/const3.html#creating_immutable_data