Up until today, I had assumed that it was the generator.__next__ method that was associated with the compiled body. But in writing my response, I investigated and discovered

>>> def gf(): yield None

>>> gf().gi_code is gf.__code__
True

Then i realized that the simple call protocal -- a callable is an object with an executable __call__ method -- makes the magic simpler than I thought. Generator functions must have a special __call__ method that simply creates and returns a generator instance with the code object attached (instead of executing the code).

Since code objects are referred to in various places (compile(), exec(), probably def statement doc), I agree that there should be a minimal glossary entry. One can't really understand generator functions and generators without knowing that def statements create both a function object and an attached code object, but that they can operate somewhat separately.