[Issue 10850] Inout substituted incorrectly for delegates/fptrs in inout function signature

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=10850

--- Comment #6 from Sobirari Muhomori <dfj1esp02 at sneakemail.com> ---
(In reply to timon.gehr from comment #3)
> What are you referring to? The current behaviour of DMD is indeed to
> consider 'inout' bound to the outermost inout function signature

I mean, it shouldn't work that way.

> All of these ad-hoc fixes are of a certain minimum stupidity because there
> is no right answer here (more precisely, the 'right' answer would need to
> change the surface syntax, because there would need to be more than one
> inout qualifier).

The right answer is the type system with existing syntax should be sound even
if it can be sound with different syntax.

> In any case, this suggestion (as I understand it) is indeed particularly
> stupid as it is unsound:
> 
> const(int)** foo(inout(int)** x){
>     // inout treated as const from nested context:
>     const(int)** bar(){ return x; }
>     return bar();
> }
> 
> (This is the same type coercion underlying the previous proof of
> unsoundness.)

Indeed, it's a const casting and should obey const casting rules as described
in issue 4251: if conversion happens, everything beyond the first indirection
should become const. I thought, inout already takes care of that, but it
happened to be more flexible.

> > assert(foo(&a,x=>x) is &a); looks like duplicate of issue 11772 (works for
> > function, but not for delegate)
> 
> If anything, then issue 11772 is the duplicate.

That issue is about discrepancy between function and delegate behavior, it has
nothing to do with inout being bound to outer function.

--