Is it possible to detect if a type exists?

[Qi]

Assume we can use any standard technical (macro, template, etc),
is it possible to know that if type SomeType exists at compile time?

SomeType is,
either not defined, i.e, the symbol SomeType doesn't exist at all,
or was defined as a class, so I can fetch any pre-defined information
from it.

I highly doubt its feasibility. Because as long as the type doesn't
exist, the compile will complain "SomeType" can't be found.

Any magic (while be standard)?

 

[Cholo Lennon]

Assume we can use any standard technical (macro, template, etc),
is it possible to know that if type SomeType exists at compile time?

SomeType is,
either not defined, i.e, the symbol SomeType doesn't exist at all,
or was defined as a class, so I can fetch any pre-defined information
from it.

I highly doubt its feasibility. Because as long as the type doesn't
exist, the compile will complain "SomeType" can't be found.

Any magic (while be standard)?

AFAIK, you can't. The closest approach is Boost.TypeTraits or some
compiler intrinsic type traits.

Regards