Incorrect local reusage?

[pufferfish101007]

It seems that sometimes locals are reused for things that they're not meant to be. Is fixed by enabling SSA, but disabling variable merging doesn't fix it.

Sample reproducer:
https://scratch.mit.edu/projects/1384687851/
https://hyperquark.edgecompute.app/projects/1384687851

Loops endlessly, or sometimes makes no change to the variable.

First observed on #73 but happens on v0.0.10 as well.

Reproducer can probably be minimised further.

[pufferfish101007]

This is probably a result of variables being written to their global, and then being read from their unchanged procedures_argument