* Classes can extend JS constructor functions
Now ES6 classes can extend ES5 constructor functions, although only
those written in a JS file.
Note that the static side assignability is checked. I need to write
tests to make sure that instance side assignability is checked too.
I haven't tested generic constructor functions yet either.
* Test static+instance assignability errors+generics
Note that generics do not work.
* Cleanup from PR comments
* Even more cleanup
* Update case of function name
Nathan Shively-Sanders
29ca93ba48