The following valid `ns` gen-class form is reported as invalid by spec:
This is because the ns spec assumes that all class names can be represented by simple-symbols, while in reality some can only be represented by strings.
Approach: Pull out spec for class identifiers which can be either a simple-symbol (class name) or a string and use that in signature (which is used for both gen-class constructors and methods.
Nicola: Good catch, thanks for the report!
Alex: argtype is a pretty general name to grab at the top level spec ns. How about something like class-ident?