Is there any reason why this isn't allowed:

alias f = (x => x);

but this is:

template A(alias B) { alias A = B; }
alias f = A!(x => x);

???

On 01/13/2013 08:55 PM, Peter Alexander wrote:
> Is there any reason why this isn't allowed:
>
> alias f = (x => x);
>
> but this is:
>
> template A(alias B) { alias A = B; }
> alias f = A!(x => x);
>
> ???

No. It is a gratuitous grammar limitation.

On Sun, Jan 13, 2013 at 9:07 PM, Timon Gehr <timon.gehr@gmx.ch> wrote:
> On 01/13/2013 08:55 PM, Peter Alexander wrote:
>>
>> Is there any reason why this isn't allowed:
>>
>> alias f = (x => x);
>>
>> but this is:
>>
>> template A(alias B) { alias A = B; }
>> alias f = A!(x => x);
>>
>> ???
>
>
> No. It is a gratuitous grammar limitation.

The same limitation forbids:

alias __traits(whatever, ...) result;

The grammar says:

AliasDeclaration:
    alias BasicType Declarator

(and others, but this is the one limiting you). BasicType should be replaced by PrimaryExrpession, or something like that.

On 01/13/2013 09:38 PM, Philippe Sigaud wrote:
> On Sun, Jan 13, 2013 at 9:07 PM, Timon Gehr <timon.gehr@gmx.ch> wrote:
>> On 01/13/2013 08:55 PM, Peter Alexander wrote:
>>>
>>> Is there any reason why this isn't allowed:
>>>
>>> alias f = (x => x);
>>>
>>> but this is:
>>>
>>> template A(alias B) { alias A = B; }
>>> alias f = A!(x => x);
>>>
>>> ???
>>
>>
>> No. It is a gratuitous grammar limitation.
>
> The same limitation forbids:
>
> alias __traits(whatever, ...) result;
>
> The grammar says:
>
> AliasDeclaration:
>      alias BasicType Declarator
>
> (and others, but this is the one limiting you). BasicType should be
> replaced by PrimaryExrpession, or something like that.
>

I think it should be roughly:

alias TemplateArgument Identifier;
alias Identifier=TemplateArgument;


Note: The current grammar allows

alias int x = 2;

Which does not make any sense.