partial review for const and final

I've been unable to run tests, so I'd love someone to take a look there.
`{bool canIgnore: false, bool isError: true}` won't assign the value to `this.canIgnore` and `this.isError`. You need to set them explicitly as before. I believe if the variable is defined `final`, it can only be initialized in the constructor arguments. Thus, not sure if we can declare named optional arguments  as final.