Report the provenance of TyThings
One thing we are slightly nervous about regarding our resolution to #14396 (closed) is whether or not there will be a difficult to understand bug stemming from the fact that we may silently pick up an hs-boot TyThing, depending on when you do a lookup. You may be able to find the information by printing the TyThing with pprTyThing, but nothing is going to tell you, in the face, "Hey! This came from a boot file!"
So, simonpj suggested that we extend the TyThing pretty-printer to say where a TyThing came from. This is a good question. The big question: where will we put the provenance? There are two possibilities:
- Add a field in each constructor TyThing recording the provenance (this feels like a disruptive to an otherwise very simple union)
- Add a field to each of the constructors Id, ConLike, TyCon, CoAxiom (this involves a lot more typing, but these constructors already have lots of fields so it's not as disruptive)
The provenance will, for now, look something like:
newtype TyThingSrc = TyThingSrc {
tyThingFromBoot :: Bool
}and then TcIface will be extended to know if we're in boot and will fill things in accordingly.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.2.1 |
| Type | Task |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
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