Re: [boost] [typeof] Limitations in BOOST_TYPEOF_NESTED_TYPEDEF for VC8.0

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2006-05-12 19:17:42

David Abrahams wrote:
> "Peder Holt" <peder.holt_at_[hidden]> writes:
> 
> 
>>It turns out that BOOST_TYPEOF_NESTED_TYPEDEF has a problem when used inside
>>functions on VC8.0 (possibly other compilers as well)
>>This is because BOOST_TYPEOF_NESTED_TYPEDEF internally defines a member
>>template:
>>
>>struct a {
>>  template<typename T>
>>  struct b{
>>  };
>>};
>>
>>VC8.0 doesn't handle this (error C2892: local class shall not have member
>>templates)
>>
>>It is possible to avoid this problem, but this would cripple
>>BOOST_TYPEOF_NESTED_TYPEDEF because it would reintroduce the
>>BOOST_TYPEOF_LIMIT_SIZE limitation on the expression complexity.

>>The alternative is to disallow NESTED_TYPEDEF inside functions, and
>>write a note on this in the docs. Is this acceptable?

Here's my vote for this one!

> 
> Didn't I post a syntax during the review that avoids the need for this
> macro?
> 

IIRC it was a different one. NESTED_TYPEDEF was recently introduced for 
Spirit typeof support, because it doesn't ICE VC7.1 and doesn't provoke 
strange ADL issues with VC8.
It can't be used in all contexts but therefore does (nearly) not impose 
any restrictions on the expression complexity.

Regards,

Tobias