Question

I’m dealing with a template, it’s very simple. This is the current structure:

//primary template
template<typename T> 
const T bit_cast(const BitExpr* p);    

//specialization
template<> 
inline const BitBinExpr* bit_cast<BitBinExpr*>(const BitExpr* p) {
    if (p->type == XOR || p->type == AND)
        return static_cast<const BitBinExpr*>(p);
    return nullptr;
}
// more specializations follow

But Visual Studio insists that this is not valid. However, when the parameter and return types were not const, this worked just fine. How can I convince VS to accept this code?

Answer 1

This seems to have cropped up a lot lately. These two types are not the same

const BitBinExpr* // BitBinExpr is constant

and

typedef BitBinExpr* T;
const T           // pointer is constant

Maybe this is what you are looking for

template<typename T> const T bit_cast(const BitExpr* p);    
template<> inline const BitBinExpr *const bit_cast<const BitBinExpr *const>(const BitExpr* p) {
    if (p->type == XOR || p->type == AND)
        return static_cast<const BitBinExpr*>(p);
    return nullptr;
}