swap! subvec breaks vector structure

[kennytilton]

This sequence:

(let [q (atom [])
        qpush (fn [q val] (swap! q conj val))
        qpop (fn [q]
               (let [val (first @q)]
                 (swap! q #(doall (subvec % 1)))
                 val))]
    (qpush q 0)
    (qpush q 1)
    (let [p1 (qpop q)]
      (qpush q 2) ;; <- necessary ingredient
      (let [p2 (qpop q)]
        (prn :qpop2 p2)
        (prn :q @q))))

...fails like this during the second qpop:

[VERBOSE-2:ui_dart_state.cc(209)] Unhandled Exception: RangeError (index): Invalid value: Not in inclusive range 0..2: 3
#0      List.[] (dart:core-patch/array.dart:121:36)
#1      PVIterator.current (package:matrix/cljd-out/cljd/core.dart:12525:13)
#2      iterator_seq (package:matrix/cljd-out/cljd/core.dart:27415:66)
#3      IteratorSeq.$_rest$0 (package:matrix/cljd-out/cljd/core.dart:12172:51)
#4      IteratorSeq.$_next$0 (package:matrix/cljd-out/cljd/core.dart:12183:38)
#5      next (package:matrix/cljd-out/cljd/core.dart:29328:52)
#6      dorun$ifn.$_invoke$1 (package:matrix/cljd-out/cljd/core.dart:23451:24)
#7      doall$ifn.$_invoke$1 (package:matrix/cljd-out/cljd/core.dart:23406:23)
#8      main.qpop$1.<anonymous closure> (package:matrix/cljd-out/tiltontec/main.dart:44:31)
#9      Atom.$_swap$BANG_$1 (package:matrix/cljd-out/cljd/core.dart:3683:28)
#10     swap$BANG_$ifn.$_invoke$2 (package:matrix/cljd-out/cljd/core.dart:33376:17)
#11     main.qpop$1 (package:matrix/cljd-out/tiltontec/main.da<…>

Change the doall to do and it fails printing the vector after the second qpop:

[VERBOSE-2:ui_dart_state.cc(209)] Unhandled Exception: RangeError (index): Invalid value: Not in inclusive range 0..2: 3
#0      List.[] (dart:core-patch/array.dart:121:36)
#1      pv_reduce$ifn.$_invoke$5 (package:matrix/cljd-out/cljd/core.dart:30565:43)
#2      SubVec.$_reduce$2 (package:matrix/cljd-out/cljd/core.dart:16947:35)
#3      print_sequential (package:matrix/cljd-out/cljd/core.dart:30290:47)
#4      SubVec.$_print$1 (package:matrix/cljd-out/cljd/core.dart:16746:24)
#5      pr$ifn.$_invoke$vararg (package:matrix/cljd-out/cljd/core.dart:30069:43)
#6      IFnMixin_XZ.$_apply$1 (package:matrix/cljd-out/cljd/core.dart:6701:14)
#7      apply$ifn.$_invoke$2 (package:matrix/cljd-out/cljd/core.dart:18006:51)
#8      prn$ifn.$_invoke$vararg (package:matrix/cljd-out/cljd/core.dart:30355:23)
#9      IFnMixin_Z.$_invoke$2 (package:matrix/cljd-out/cljd/core.dart:6902:14)
#10     main (package:matrix/cljd-out/tiltontec/main.dart:54:29)
#11     _runMainZoned.<anonymous closure>.<anonymous closure> (dart:<…>

[kennytilton]

FWIW, this works:

(defn fifo-pop [q]
  (when-not (fifo-empty? q)
    (let [val (first @q)]
      (swap! q #(vec (rest %)))
      val)))

[dupuchba]

Fixed, thx
eadb195