Re: Re: bug/feature - emacs doesn't tell you about keys with multiple prefixes

[Richard Stallman]

    In accessible-keymaps (used by where-is-internal), there is an explicit 
check
    to remove any duplicate keymaps (i.e. the same keymap appearing under 
another
    prefix).

I don't remember the reason for this.  Perhaps the idea was that it is
supposed to tell you all the keymaps, not all the prefixes.
Preventing cycles is also necessary.

There could be an optional 3rd arg ALLOW-DUPLICATES which, if non-nil,
means that it only rejects actual cycles (where the prefix already
recorded for the same keymap is an initial segment of the new prefix).