[CLJ-1170] conj-ing x on equal values should produce equal results

Fri, 1 Mar 2013 10:04:40 -0600

I've recently have run into a WHAT behavior here is an example:

```clojure
(def head 1)
(def tail [2 3])

(= tail (rest (cons head tail))) ; true

;; Types don't really match but close enough I guess
(type tail) ; clojure.lang.PersistentVector
(vector? tail) ; true
(type (rest (cons head tail))) ; clojure.lang.PersistentVector$ChunkedSeq
(vector? (rest (cons head tail))) ; false

;; Bet then it get's ugly (I would expect them to be equal)
(= (conj tail :x) (conj (rest (cons head tail)) :x)) ; false

;; Because
(conj tail :x) ; [2 3 :x]
(conj (rest (cons head tail)) :x) ;(:x 2 3)
```

This brings me to a pretty surprising behavior, which is conj-ing
equal values produce non-equal results:

```clojure
(= '(2 3) [2 3]) ; true
(= (conj '(2 3) 1) (conj [2 3] 1))
```

I think conj should either produce equal results or list and vectors with
same elements should not be equal. That would also resolve a previous
problem, although intuitively I would expect `(rest (cons x y))` to
return `y` back.

Clojure JIRA

[CLJ-1170] conj-ing x on equal values should produce equal results