ok I do not understand.

What is preventing this import std/errorcodes

from allowing me to use: raise errorcodes.RangeError instead of what Nim has?

or even why not even "import std/ErrorCodes" and having the plural in ErrorCodes.RangeError I wouldn't mind

Nothing, and it fact this works. To move to an example which actually compiles:

    import math
    
    echo fcNormal
    echo FloatClass.fcNormal
    echo math.fcNormal
    echo math.FloatClass.fcNormal

If instead you do `from math import nil` only the latter two work.