Tips on how to avoid Nim pointer instability bugs?

[japplegame]

This is a relatively well-known corner case. Different languages define the 
order of evaluation for assignments differently.

**C++:** implementation defined.

**D:** implementation defined.

**Python:** order of evaluation is left-to right, but for assignment it's 
right-to-left.

**Java:** chose left-to-right everywhere.

@Araq, what about Nim?