Rust: Improve CFG

[paldepind]

With this PR CFG creation is (attempted) to cover every relevant node in the AST. Some noteworthy additions are match expressions, closures, continue and break in loops (including with labels), if let expressions and short-circuiting binary operators.

I'm not aware of any syntax constructions that are not supported, but there probably are some bugs in there :)

[paldepind]

The short-circuiting operators are pre-ordered s.t. nested operators can be handled in a way where impossible paths are eliminated.

[hvitved]

As discussed offline, this is fine for now, but we want to change this later to use splitting.

[geoffw0]

Looks very promising!

there probably are some bugs in there :)

Hopefully when we have consistency checks and actual queries depending on this we'll discover any issues quite rapidly.

[hvitved]

Really great work, Simon!

[paldepind]

The PR is ready for re-review.

I've addressed most of the comments. I didn't fix the match/no-match edges going out of let statements. I don't understand yet why they're not picked up by the trivialPat predicate, but we can investigate that later I think :)

[hvitved]

The PR is ready for re-review.

I don't understand why the CFGs for test_nested_if and test_nested_if_match are gone in the merge commit?

[paldepind]

You're right, I didn't notice that. It could be due to the changes in the extractor or maybe some of the last changes I made broke it. Let's investigate after merging :)