How to test for equality of types?

[Matthias Walter]

On 2012-05-19 09:05, Philippe Sigaud wrote:
> On Fri, May 18, 2012 at 11:51 PM, Simen Kjaeraas <simen.kjaras at gmail.com> wrote:
> 
>> Because Wrapper!(AliasStruct).Wrap does not exist. And _error_ is not
>> equal to any other type.
> 
> Yes. Wrap is included in the complete template name (Wrapper!(Wrap))
> and has no independent existence.
> You _can_ get access to it by exposing it as an alias, as you do in AliasStruct:
> 
> struct Wrapper(Wrap)
> {
>     alias Wrap Wrapped; // cannot call it 'Wrap'
>  ...
> 
> }

Yes, of course you are right. This was my fault - after exposing it via
an alias, it prints true.

> (third case)
>>> false
>>
>>
>> And here I disagree. This prints true on 2.059. Regression?
> 
> AFAICT, this should print true.
> 
> And, concerning Artur questio, on 2.059 (Linux):
> 
>  pragma(msg, is(w._wrap.Alias == AliasStruct.Alias));//   -> true
>  pragma(msg, typeof(w._wrap).Alias.stringof); // -> MyStruct
>  pragma(msg, AliasStruct.Alias.stringof); // -> MyStruct

I would open a bug report with the following code which is a bit smaller
than my first wrong version:

=====================
module main;

struct MyStruct { }

struct AliasStruct
{
  alias MyStruct Alias;
}

struct Wrapper
{
  AliasStruct aliasStruct;
}

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(typeof(w.aliasStruct).Alias == AliasStruct.Alias));
// -> false
}
=====================

Best regards,

Matthias