constexpr overloading

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I agree that this feature is missing – I need it too.
Example:

double pow(double x, int n) {
    // calculate x to the power of n
    return ...
}

static inline double pow (double x, constexpr int n) {
    // a faster implementation is possible when n is a compile time constant
    return ...
}

double myfunction (double a, int b) {
    double x, y;
    x = pow(a, b);  // call version 1 unless b becomes a compile time constant by inlining
    y = pow(a, 5),  // call version 2
    return x + y;
}

Now I have to do this with templates:

template <int n>
static inline double pow (double x) {
    // fast implementation of x ^ n, with n a compile time constant
    return ...
}

This is fine, but I miss the overload opportunity. If I make a library function for others to use then it is inconvenient that the user has to use different function calls depending on whether n is a compile time constant or not, and it may be difficult to predict whether the compiler has reduced n to a compile time constant or not.

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