[nutate]

Oddly the first issue I came across today was folks being confused about this. I haven't gotten to the bottom of where the code is now, but this go library was messing up len == 0 vs nility and someone forked it to fix it: https://github.com/algorithmiaio/mapstructure/pull/1 It may not be a common bug but that doesn't make it less of a pitfall.

[morelisp]

No, this is a terrible idea and you're in for a world of pain. If you want to distinguish "not set" from "length zero" use a *[]T or ([]T, bool), not a nil vs. non-nil-empty []T. A nil slice is not any special kind of empty slice, it is just the most efficient representation of an empty slice.