'Build a GeneratorDescriptor for the generator returned by the
function described by *fndesc*, with type *gentype*.'

@classmethod
def from_generator_fndesc(cls, func_ir, fndesc, gentype, mangler):

    assert isinstance(gentype, types.Generator)
    restype = gentype.yield_type
    args = ['gen']
    argtypes = (gentype,)
    qualname = (fndesc.qualname + '.next')
    unique_name = (fndesc.unique_name + '.next')
    self = cls(fndesc.native, fndesc.modname, qualname, unique_name, fndesc.doc, fndesc.typemap, restype, fndesc.calltypes, args, fndesc.kws, argtypes=argtypes, mangler=mangler, inline=True)
    return self
