My chemistry teacher said hydrogen when bonded with metals has oxidation number (O.N.) of −1 except CuH: in CuH the hydrogen has O.N. +1 and the copper has O.N. −1.
But on the internet it is ubiquitously told that the O.N. of hydrogen is −1 in CuH too, and the compound's name is copper(I) hydride. I am confused which one is correct. If hydrogen has O.N. of +1 in CuH, why is it so?