Why does adding constexpr make VS2013 reject this?

Question

This code does not compile in Visual Studio 2013

template <typename X> 
constexpr //error C2144: syntax error : 'bool' should be preceded by ';'
bool Test(X x)
{
    return true;
}

However, if I remove the constexpr keyword, it does compile.

But constexpr shouldn't be a problem? since it always returns true.

What went wrong?

Answer 1

Despite the 2013 in the name, VS2013 does not purport to be a compiler targeting the C++11 standard (which was when constexpr was introduced).

The value of __cplusplus will be 201103L for a C++11 compiler.

So your compiler encounters a token it does not recognise, and issues a diagnostic.