Error when generating code for conditionals inside `If`

Consider

knl = lp.make_kernel("{[p] : 0 <= p < 2}", 
""" 
for p 
   A[p] = if(fabs(A[p] >= 1), 0, 1) 
end 
""",  
[lp.GlobalArg("A", shape=(2, ), dtype=np.float64)], target=lp.CTarget(), lang_version=(2018, 2))

print(lp.generate_code_v2(knl).device_code()

=> 

~/Documents/work/src/firedrake/src/loopy/loopy/type_inference.py in map_call(self, expr, return_tuple)
    464                         # }}}
    465 
--> 466                         raise LoopyError("Overwriting a specialized function "
    467                                 "is illegal--maybe start with new instance of "
    468                                 "InKernelCallable?")

LoopyError: Overwriting a specialized function is illegal--maybe start with new instance of InKernelCallable?

What did I do wrong?

This is related (?) to https://github.com/firedrakeproject/firedrake/issues/1464, which makes the attached (pickled) kernel which provokes this error:

import pickle
with open("foo.pickle", "rb") as f:
   knl = pickle.load(f)
print(lp.generate_code_v2(knl).device_code())

=>
in with_callable(self, function, in_kernel_callable)
    771                 print('Old: ', self.resolved_functions[function.name])
    772                 print('New: ', in_kernel_callable)
--> 773                 raise LoopyError("Use 'with_enter_edit_callables_mode' first.")
    774 
    775         # }}}

LoopyError: Use 'with_enter_edit_callables_mode' first.

foo.pickle