PUBLIC
Hi,
I'm writing a type checker plugin that should do things whenever used in the
context of a module that already has some definitions loaded. I've hacked
together the following function using internal details that I feel I should not
be using:
lookupOrigMaybe :: Module -> OccName -> TcPluginM (Maybe Name)
lookupOrigMaybe mod occ = do
hsc_env <- getTopEnv
unsafeTcPluginTcM $ liftIO $ updateNameCache (hsc_NC hsc_env) mod occ $
\cache0 -> do
let name = lookupOrigNameCache cache0 mod occ
return (cache0, name)
I would like to do this in a nicer way instead. It should be enough to check
that the given module is already loaded, since for my use case, if the module
is there but the name isn't, then all bets are off and my plugin might as well
just error out. So I was hoping I could use `findImportedModule` followed by
`lookupOrig`, but alas, `findImportedModule` fails me in one of two ways:
1. If I don't specify the package (i.e. use `NoPkgQual`),
`findImportedModule` seems to return a `Found{}` result even when the module
isn't actually loaded yet, leading to `lookupOrig` failing:
attempting to use module 'main:Cortex.Stem.Relation.Types'
(Cortex.Stem.Relation.Types) which is not loaded
1. If I do specify the package (using `ThisPkg`), then `findImportedModule`
chokes in situations when the given unit would come "later" in the dependency
graph than the currenty processed one:
ghc-mu-core-to-exp: panic! (the 'impossible' happened)
GHC version 9.5.20220830:
findImportModule
Cortex.Stem.Relation.Types
"main"
Just ghc-bignum
main
[ghc-bignum, cortex-prim]
Call stack:
CallStack (from HasCallStack):
callStackDoc, called at compiler/GHC/Utils/Panic.hs:188:37 in
ghc-lib-0.20220830-FvKByKwp6ri5ICk6wiQO8W:GHC.Utils.Panic
pprPanic, called at compiler/GHC/Unit/Finder.hs:160:32 in
ghc-lib-0.20220830-FvKByKwp6ri5ICk6wiQO8W:GHC.Unit.Finder
Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug
So my question then, is what is the recommended way of looking up a loaded
definition opportunistically from a type checker plugin?
Thanks,
Gergo
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