The following currently works on master:
$ cljs -R:cljs/dev -re node
cljs.user=> (defprotocol IFoo (delete [_]))
false
cljs.user=> (extend-type default IFoo (delete [_] 17))
nil
cljs.user=> (delete #js {})
17
But, it didn't with 1.10.439:
`
$ cljs -R:cljs/rel -re node
ClojureScript 1.10.439
cljs.user=> (defprotocol IFoo (delete [_]))
false
cljs.user=> (extend-type default IFoo (delete [_] 17))
nil
cljs.user=> (delete #js {})
repl:13
throw e6600auto__;
^
TypeError: Cannot read property 'object' of undefined
at cljs$user$delete (repl:18:40)
at repl:1:107
at repl:9:3
at repl:14:4
at ContextifyScript.Script.runInThisContext (vm.js:50:33)
at Object.runInThisContext (vm.js:139:38)
at Domain.<anonymous> ([stdin]:76:38)
at Domain.run (domain.js:242:14)
at Socket.<anonymous> ([stdin]:73:29)
at emitOne (events.js:116:13)
`
This was evidently fixed as a side effect of CLJS-2960.
This ticket asks that a test be added to ensure this correct behavior going forward.
