But there is code, and it can be type hinted and checked just as easily. First of all, any constructed classes usually inherit from some parent class, which can be checked for easily.

Second, types can be constructed on the fly as well. Agreed, they will not show up in an IDE, but a) they can (and should!) be unit tested, and b) while I do value editor type-checking I value my time, and streamlined process (i.e. not having to have the extra step of code generation each time I change the spec) much more.

And finally, if you version both spec and the generated code you run into a danger of them diverging without realising. If you absolutely must have the code generation, make sure not to commit the generated code, and rebuild each time you change the spec.