crash with microgpt.py

Hi,

`codon` (freshly installed) crashes (`Segmentation fault: 11`) on my mac (with latest os) with this file:
https://gist.github.com/karpathy/8627fe009c40f57531cb18360106ce95

Note:
1. please launch `python3` first with this program as it will download an input file (`codon` is enable to do that) that can be reused later
2. before launching with `codon`, comment out line 32: ``` __slots__ = ('data', 'grad', '_children', '_local_grads') # Python optimization for memory usage```, as this will prevent codon from compiling

I think it's a good testbed for `codon`, let's see how it improves time of completion...