lists, plain conses and length

[T.V Raman]

Ran into this while trying to distinguish a cons from a list:

Try this:

(setq a (cons 1 2)) => (1 . 2)
(consp a) => t
(listp a) => t
(length a)=> Debugger entered--Lisp error: (wrong-type-argument listp 2)

Q: how does one distinguish a cons from a list.
The error  message for length may need fixing since it says the
argument passed to it is not a list (it's correct) but then listp is wrong?
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♉ Id: kg:/m/0285kf1  🦮

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♉ Id: kg:/m/0285kf1  🦮

-- 
♉ Id: kg:/m/0285kf1  🦮