Incorrect hash when conj-ing onto the value returned by filter/remove etc

Description

The following code produces the correct result in Clojure but incorrect results in ClojureScript:

(let [log (fn [xs]
              (prn (hash xs) (count xs))
              xs)]
    (-> []
        (conj 1)
        (conj 2)
        log
        (->> (remove #{1}))
        log
        (->> (remove #{2}))
        log
        (conj 3)
        log
        (conj 4)
        log
        (conj 5)
        log))

Clojure produces the following output:

156247261 2
829981563 1
-2017569654 0
-1154116787 1
-733651870 2
1036804101 3

ClojureScript produces the following output:

1185709346 2
-1917711765 1
-2017569654 0
-1025653387 1
-1025653387 2
-1025653387 3

I expect the hash code to change as I conj items onto the list. Instead, the hash code stays the same even though we can se that the result of "count" changes.

At the time of writing, I host a leiningen project on my github user that contains the exact setup and a README for how I run the code:

https://github.com/augustl/cljs-issue-filter-conj-hashcode

Environment

java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

Activity

David Nolen

December 30, 2015 at 10:57 AM

fixed https://github.com/clojure/clojurescript/commit/15f9bbe59b47312f451b90972864a37a1c2246d2

Thomas Heller

December 28, 2015 at 11:04 PM

Appears to be type related, I added the type for reference:

(let [log (fn [xs]
            (prn (hash xs) (count xs) (type xs))
            xs)]
  (-> []
      (conj 1)
      (conj 2)
      log
      (->> (remove #{1}))
      log
      (->> (remove #{2}))
      log
      (conj 3)
      log
      (conj 4)
      log
      (conj 5)
      log))

Clojure:

156247261 2 clojure.lang.PersistentVector
829981563 1 clojure.lang.LazySeq
-2017569654 0 clojure.lang.LazySeq
-1154116787 1 clojure.lang.PersistentList
-733651870 2 clojure.lang.PersistentList
1036804101 3 clojure.lang.PersistentList

ClojureScript:

1185709346 2 cljs.core/PersistentVector
-1917711765 1 cljs.core/LazySeq
-2017569654 0 cljs.core/LazySeq
-1025653387 1 cljs.core/Cons
-1025653387 2 cljs.core/Cons
-1025653387 3 cljs.core/Cons

import

December 28, 2015 at 7:14 PM

Comment made by: augustl

Adding some extra details.

Full project.clj:

(defproject cljs-bug "0.1.0-SNAPSHOT"
  :dependencies [[org.clojure/clojure "1.7.0"]
                 [org.clojure/clojurescript "1.7.170"]]
  :plugins [[lein-cljsbuild "1.1.2"]]
  :main cljs-bug.cli
  :profiles {:dev {:cljsbuild {:builds [{:source-paths ["src"]
                                         :compiler {:output-to "target/classes/public/app.js"
                                                    :output-dir "target/classes/public/out"
                                                    :main "cljs-bug.web"
                                                    :asset-path "target/classes/public/out"
                                                    :optimizations :none
                                                    :recompile-dependents true
                                                    :source-map true}}]}}})

Full src/cljs_bug/cli.clj code:

(ns cljs-bug.cli
  (:require [cljs-bug.bug :as bug]))

(defn -main [& args]
  (bug/demonstrate))

Full src/cljs_bug/web.cljs code:

(ns cljs-bug.web
  (:require [cljs-bug.bug :as bug]))

(enable-console-print!)
(bug/demonstrate)

Resize work item view side panel

Completed

Details

Assignee

Unassigned

Reporter

import

Affects versions

1.7.145

Priority

Major

Created December 28, 2015 at 7:12 PM

Updated December 30, 2015 at 10:57 AM

Resolved December 30, 2015 at 10:57 AM