1575639 - Convert most source-related positions to be SourceActor locations instead of Source locations

Status: NEW

(DevTools :: Debugger, task, P3)

Description

[Logan Smyth [:loganfsmyth]]

Right now all of our locations are in the form

type SourceLocation = {
  sourceId: SourceId,
  line: number,
  column: number,
};

which is somewhat at odds with what we want in many cases, because we'd like this data to be associated with a specific SourceActorId instead. For instance, the sourceMap worker currently uses the SourceId as the primary key for a generated source instead of the SourceActorId purely because so much of our code references Source-specific locations.

We should try to migrate most of our source-code-related processing to use locations for specific actors. We'll still also want SourceLocation alongside SourceActorLocation, but it would be used for a much smaller subset of places.