Distinguish between statements and expressions

[robrix]

This doesn't apply to all languages, but it would be nice to distinguish between statements and expressions at the level of abstract domains.

The goal would be to avoid polluting the abstract domain with stuff that doesn't actually relate to it, e.g. imports.

[robrix]

One possibility is simply to model them with instrumentation: an out-of-band effect notified of various events (e.g. an import was reached), with unit returned by each.