Returns true if this matches domain and
code, false otherwise.
In particular, when this is null, false will be returned.
If domain contains a `FAILED` (or otherwise generic) error code, you should generally not check for it explicitly, but
should instead treat any not-explicitly-recognized error code as being equilalent to the `FAILED` code. This way, if the domain is
extended in the future to provide a more specific error code for a certain case, your code will still work.
| this |
a Error or null |
| domain |
an error domain |
| code |
an error code |
|
whether this has |