Use static_assert to check types passed to macro

Question

I unfortunately have several macros left over from the original version of my library that employed some pretty crazy C. In particular, I have a series of macros that expect certain types to be passed to them. Is it possible to do something along the lines of:

static_assert(decltype(retval) == bool);

And how? Are there any clever alternatives?

Yes I'm aware macros are bad. I'm aware C++ is not C, etc.

Update0

Here is some related code, and the source file. Suggestions are welcome. The original question remains the same.

Answer 1

I found this to be the cleanest, using @UncleBens suggestion:

#include <type_traits>

static_assert(std::is_same<decltype(retval), bool>::value, "retval must be bool");

Answer 2

Disclaimer: This is a bad answer, there are definitely far better solutions. Just an example :)

It is bound to be already implemented, but it's trivial to implement yourself;

template <class T1, class T2> struct CheckSameType; //no definition
template <class T> struct CheckSameType<T,T>{}; //

template <class T1, class T2>
AssertHasType(T2)
{
   CheckSameType<T1, T2> tmp; //will result in error if T1 is not T2
}

To be used like this:

AssertHasType<bool>(retval);

Alternative (suggested by GMan):

template <class T1, class T2> struct SameType
{
    enum{value = false};
}
template <class T> struct SameType<T,T>
{
    enum{value = true};
}; 

To be used like

static_assert(SameType<decltype(retval), bool>::value);

Answer 3

It appears you need decltype because you've got an expression, but want to verify a type. There are already enough ways to do that now (C++03). For instance, to check a bool

inline void mustBeBool(bool) { }
template<typename T> inline void mustBeBool(T t) { & (&t); } // Takes address of rvalue (&t)

// Use:
#define DifficultMacro(B) do { mustBeBool(B); foo(B); } while (false)