JS: New query: missing await

[asgerf]

Adds a query to flag cases where a promise was used, but where the intention most likely to use the result of the promise instead.

Null checks are particularly interesting here. async functions never return null, and so a null check will silently fail.

We use the call graph and static types to recognize promises, although I'm not sure how much use we get from the static types are here, as we probably only flag what the type checker would have flagged anyway. As seen here it gets noisy if we assume something of a promise type is non-nullable, so we can't use them to flag null checks.

Contains a drive-by change to getImmediatePredecessor to make it step through phi nodes whose operands are all refinements of the same value. I couldn't resist calling such nodes rephinement nodes.

Still need to run an evaluation, especially of the second commit.

[max-schaefer]

Nice idea! A few initial thoughts.

[asgerf]

Evaluation looks ok - there is a slight cost of the change to getImmediatePredecessor and some new (boring) results from the range analysis as a result.

[max-schaefer]

@mchammer01: apologies, I merged this without realising that you hadn't reviewed the query help yet. The preview is still available here.

[mchammer01]

I'll take a look when I can (have been having back-to-back meetings all week and wasn't in yesterday).

[mchammer01]

@asgerf - this LGTM but you need to add this new query to the change-notes/1.24/analysis-javascript.md file.