ObservableArray.prototype.set throws an error #83
Description
With the changes to make class fields observable, setting expand properties using .set is now broken. Here is an example:
class Foo extends ObservableArray{}
const foo = new Foo();
foo.set("count", 3)This is the error thrown:
Uncaught TypeError: Cannot read property 'count' of undefined
at Object.get Foo[].count [as get] (define.js:809)
at Object.defineProperty (can-observable-array.js:67)
at Function.defineProperty (<anonymous>)
at Object_defineNamedPrototypeProperty (define.js:81)
at Function.define.property (define.js:410)
at Object.define.expando [as defineExpando] (define.js:1167)
at Proxy.setKeyValue (mixin-mapprops.js:57)
at Proxy.set (mixin-mapprops.js:108)
at eval (eval at TodoList (observable-object-test.js:NaN), <anonymous>:4:9)
at eval (eval at TodoList (observable-object-test.js:NaN), <anonymous>:5:2)