Fixing const arrays

[kenji hara]

Posted a test patch to realize the suggestion.
https://github.com/D-Programming-Language/dmd/pull/554

Kenji Hara

2011/12/11 kenji hara <k.hara.pg at gmail.com>:
> OK. I agree to the suggestion.
>
> I've been afraid that increasing IFTI rule is making the language
> learning difficult.
> It comes from the experience from implementing inout deduction for
> template function.
>
> But also it is useful that removing top const when passing arguments by value.
> C++ precedent convinced me.
>
> Thanks.
>
> Kenji Hara
>
> 2011/12/11 kenji hara <k.hara.pg at gmail.com>:
>> 2011/12/11 Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org>:
>>> On 12/10/11 4:31 PM, kenji hara wrote:
>>>>
>>>> Treating whole constant arrays as ranges by automatically shedding the
>>>> top-level const is good.
>>>> But realizing it by language semantic change is definitely bad.It
>>>> breaks IFTI rule, and adding special case will make difficult to learn
>>>> language.
>>>>
>>>> Instead of language change, we can add specializations that receive
>>>> non-ranges and convert them to ranges by removing top-level const.
>>>> I believe that it is Phobos issue and is never the issue of language.
>>>
>>>
>>> I should add there is precedent. C++ also removes top-level const when
>>> passing objects by value to templates. Deducing top-level const with
>>> pass-by-value is inherently nonsensical.
>>>
>>> Andrei
>>>
>>
>> Hmm, it's for sure.
>> ----
>> void print_type(int){}
>>
>> template <typename T>
>> void f(T p)
>> {
>>    int n;
>>    p = &n;     // OK, head is mutable
>>    //*p = 10;  // NG, tail is const
>>    print_type(p);
>>                // Error: need explicit cast from int const * to int
>>                // T is deduced as int const * == top const is removed
>> }
>> int main()
>> {
>>    int n;
>>    int const * const p = &n;
>>    f(p);
>>    return 0;
>> }
>>
>> Kenji