Access an array/map with index of enum class type (something like a constexpr map)

Question

Say I have a

enum class foo : std::uint32_t {
    a = 4711,
    b = 815,
    ...
};

with n enumeration constants. Assume that there actual numerical value is important. I need to pass precisely one value of type T to a function for every enumeration constant in foo.

I really would like to pack them together, for example in a std::array<T, n> arr, and access the T value corresponding to the enumeration constant a by arr[a], and so on.

This would be possible, for example, if the constants would be valued by 0, 1, 2, .... Then I could write arr[static_cast<std::underlying_type_t<foo>(a)]. However, even then this is not as easy to read as arr[a].

So, is there some kind of "constexpr map or something similar? The solution I'm looking for should not be specific for foo, but quite generic, since I have multiple such foo enum classes.