[cfe-dev] Template error without instantiation?

[Sebastian Redl]

On 25.04.2013, at 09:58, Handa, Ramneek wrote:

> Thanks John. 
> 
> Making small immaterial adjustments to code:
> 
> x--start--x
> 
> class A {};
> 
> class B {};
> 
> void THIS_IS_AN_ERROR(A& myexp) {
> }
> 
> template <typename T>
> void mytest(const B &value)
> {
>   THIS_IS_AN_ERROR(A(value));
> }
> 
> template <typename T>
> void mytest(const T &value) 
> {
>   //Do something useful, ignore what we had here earlier
> }
> 
> x--end--x
> 
> It's a case of template specialization where I would like the compiler
> to throw an error if B is being passed to mytest.
> If not I would like it to do the *useful thing*.

Just drop the mytest overload for B and drop this in the generic version:

static_assert(!std::is_same<T, B>::value, "Don't instantiate with B.");

Sebastian