How to test for equality of types?

[Kenji Hara]

On Saturday, 19 May 2012 at 18:17:16 UTC, Matthias Walter wrote:
> On 2012-05-19 15:28, Philippe Sigaud wrote:
>> On Sat, May 19, 2012 at 12:23 PM, Matthias Walter
>> <xammy at xammy.homelinux.net> wrote:
>> 
>>> I would open a bug report with the following code which is a 
>>> bit smaller
>>> than my first wrong version:
>>>
>>> =====================
>> (...)
>>>  pragma(msg, typeof(w.aliasStruct).Alias.stringof); // -> 
>>> "MyStruct"
>>>  pragma(msg, AliasStruct.Alias.stringof); // -> "MyStruct"
>>>  static assert(is(typeof(w.aliasStruct) == AliasStruct)); // 
>>> -> true
>>>  static assert(is(typeof(w.aliasStruct).Alias == 
>>> AliasStruct.Alias));
>>> // -> false
>>> }
>> 
>> Seems like a pb concerning whether Alias is a type or a 
>> symbol. See
>> A,B,C,D below:
>> 
>> void main()
>> {
>>  Wrapper w;
>> 
>>  pragma(msg, typeof(w.aliasStruct).Alias.stringof); // -> 
>> "MyStruct"
>>  pragma(msg, AliasStruct.Alias.stringof); // -> "MyStruct"
>>  static assert(is(typeof(w.aliasStruct) == AliasStruct)); // 
>> -> true
>>  static assert(is(w.aliasStruct.Alias == AliasStruct.Alias)); 
>> // -> true
>> 
>>  alias typeof(w.aliasStruct) A; // -> OK
>>  //alias typeof(w.aliasStruct).Alias B; // -> NOK
>>  //alias A.Alias C; // -> NOK
>>  alias w.aliasStruct.Alias D; // -> OK
>> 
>>  static assert(is(A.Alias == AliasStruct.Alias)); // -> true
>>  //static assert(is(B == AliasStruct.Alias));
>>  //static assert(is(C == AliasStruct.Alias));
>>  static assert(is(D == AliasStruct.Alias)); // -> true
>> }
>> 
>> I think A is enough for your need, but I don't get why B and C 
>> are not
>> accepted (DMD 2.059, Linux)
>> 
>
> Using the current git version of dmd I realized that C works! 
> Hence, as
> a workaround it can be used by creating a local alias A and 
> subsequently
> using A.Alias in the is-expressions. But it seems odd that
>
> "alias typeof(X).A B;" does not work but
> "alias typeof(X) Y; alias Y.A B;" does.
>
> Is this considered as a bug?
>
> Best regards,
>
> Matthias

It seems to me that is a regression by fixing bug 6475.
Now I'm trying to fix them.