Small dyn_cast embellishment

It appears that LLVM has quite a number of dyn_casts (which I find quite
natural) The suggested idiom:

   if (ConstantExpr* ce = dyn_cast<ConstantExpr>(*j)) {

is fine, and IIRC even used in TC++PL, but it occured to me that we can do
even better:

   if (dyn_caster<ConstantExpr> ce = *j) {

where dyn_caster is defined like this:

    template<class T>
    class dyn_caster
        template<class T2>
        dyn_caster(T2& t)
        : m_ptr(dyn_cast<T>(t))

        T& operator*() const { return *m_ptr; }
        T* operator->() const { return m_ptr; }
        operator void*() const { return m_ptr; }
        T* m_ptr;

This allows to type the type name only once, not twice. I'm not sure if this
good idea yet, but though I'd just throw it in, in case anybody will be

- Volodya

That is definitely interesting and would reduce some clutter. I need to
think about this a bit. I don't really like the name dyn_caster, maybe
dyn_casted? I'm not sure. :slight_smile: The nice thing about the dyn_cast way of
doing things is that it IS an idiom that people are used to.