[JASS] BlzGroupAddGroupFast seems broken

[Barade]

Whenever I work with BlzGroupAddGroupFast or use system using it, it seems completely broken. The target group stays empty and FirstOfGroup returns null.
For example with this function:

function CopyGroup takes group whichGroup returns group
    local group copy = CreateGroup()
    //call BlzGroupAddGroupFast(copy, whichGroup) // seems broken
    call GroupAddGroup(whichGroup, copy)
    return copy
endfunction

or are the parameter names simply wrong and reversed?

 

[Uncle]

Looks like you got the parameters backwards. The Lua plugin for VSC has intellisense for that:

I imagine the vJass plugin does the same thing.