So what does (inout int = 0) do?

[Kenji Hara via Digitalmars-d]

2016-04-15 22:41 GMT+09:00 Andrei Alexandrescu via Digitalmars-d <
digitalmars-d at puremagic.com>:

> On 04/15/2016 06:50 AM, Kenji Hara via Digitalmars-d wrote:
>
>>
>>
>> You should recall the history of inout.
>> http://wiki.dlang.org/DIP2
>>
>> At first, It has designed to temporarily squash mutable/const/immutable
>> qualifiers on function argument inside function body. Therefore when
>> inout qualifier appears in function return type, but doesn't on
>> parameter types, we defined it an error.
>>
>> However, I concluded that we can remove the restriction. When an inout
>> object arises from thin air, no one holds the qualifier of its real
>> instance. It means, the returned inout object can be converted to
>> arbitrary qualifiers without type system breaking.
>>
>> Two years ago I opened an enhancement issue:
>> https://issues.dlang.org/show_bug.cgi?id=13006
>>
>> And posted a pull request.
>> https://github.com/D-Programming-Language/dmd/pull/3740
>>
>
> I do recall the history. The enhancement is sensible in a frame of mind
> "we need to keep inout" but I'm looking at top level and thinking, crap we
> can put up with a little duplication if we get rid of inout. It's just a
> prime example of apparently simple idea gone bonkers.
>
> In all of my recent code I've avoided inout and didn't miss it one bit.
> There's no need for it - I replace it with one-liners that forward to
> template functions, which in turn deduce qualifiers and all is great.


Didn't you use array.dup until now? It's a good example to handle
qualifiers with inout.
It's not sensible at all, inout is already well-defined and has much power
in D's type system.
Removing it is just a foolish idea.

If you worry the future of Phobos written in D, first you would need to
think about @safe.
It's yet not well defined/implemented by compiler, and many Phobos code are
marked as @trusted.
Does it has lower priority than complain to a small hack for the *current*
inout limitation?

I just cannot agree your argument.

Kenji Hara
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