Whenever any deftype/defrecord defines methods on Object the CLJS compiler will emit an invalid type annotation which Closure complains about when running with type checking enabled.
(ns demo.type)
(deftype Foo [a b]
Object
(foo [this x]
x))
produces this JS
/**
* @constructor
* @implements {demo.type.Object}
*/
demo.type.Foo = (function (a,b){
this.a = a;
this.b = b;
});
produces the warning
Bad type annotation. Unknown type demo.type.Object
Looking at the analyzer data suggests that it indeed resolves incorrectly.
...
:defs
{Foo
{:num-fields 2,
:protocols #{demo.type/Object},
:name demo.type/Foo,
:file "demo/type.cljs",
:end-column 13,
:type true,
:column 10,
:line 3,
:record false,
:end-line 3,
:skip-protocol-flag nil},
Not entirely sure how this bypasses checks but it might be a sign that there is an overly general check for Object which does not check the namespace.
AFAICT there are no bad effects on the CLJS analyzer/compiler. Closure does complain when type checking is enabled but otherwise seems unaffected.
Not yet sure where the issue starts, but looks like cljs.analyzer/resolve-var not correctly resolving Object without an ns, via [1].
[1]
https://github.com/clojure/clojurescript/blob/998933f5090254611b46a2b86626fb17cabc994a/src/main/clojure/cljs/core.cljc#L1669-L1673
