Custom attributes (again)

[Ary Manzana]

On 4/6/12 7:09 PM, Timon Gehr wrote:
> On 04/06/2012 12:53 PM, Walter Bright wrote:
>> On 4/6/2012 3:27 AM, Ary Manzana wrote:
>>>> @safe, @nothrow, etc., require a lot of semantic support in the
>>>> compiler. They cannot pretend to be user defined attributes.
>>>
>>> Yes they can. That's how it is done in C# and Java. In fact, IUnknown is
>>> pretending to be an interface and has semantic support in the compiler.
>>
>> All the semantics of @safe are in the compiler. None of it can be user
>> defined. There's just no point to trying to make it user defined. It's
>> like trying to make int user defined.
>>
>> IUnknown's semantics are nearly all user-defined.
>>
>
> The proposal is not to make the semantics of @safe user defined. I think
> he proposes to make 'safe' a symbol that is looked up like an user
> defined symbol.
>
> Some languages do the same for the built-in integer type.

The compiler does the same for TypeInfo, TypeInfo_ClassDeclaration or 
what ever, Object, etc.

I'm just proposing @safe to be seen as a user-defined attribute, but 
implemented in the compiler with special semantic.

I'm saying it so that lookup rules become easier: just search. No 
special cases like "if the attribute name is safe". Of course, treat the 
special cases later inside the compiler code.