As per user guide one of the restriction in annotating value is
. The binder being annotated must be declared in the current module
But when I use TH to generate the annotation above restriction is not
respected.
Below is the minimal test case to reproduce the issue
---- Ann.hs
{-# LANGUAGE TemplateHaskell #-}
module Ann where
import Language.Haskell.TH
-- {-# Ann id "Orphan Ann for id" #-} -- *Rightly produces error "Not in
scope: ‘id’"*
$(pragAnnD (ValueAnnotation 'id) [|"Orphan Ann for id"|] >>= return .
return) --* Ideally this should have produced same error as above*
---- End of Ann.hs
---- Main.hs
{-# LANGUAGE TemplateHaskell #-}
module Main where
import Ann ()
import Language.Haskell.TH
ann :: [String]
ann = $((reifyAnnotations (AnnLookupName 'id) :: Q [String]) >>= (\anns ->
[|anns|]))
--err = 'a' && True -- Uncomment to introduce compile error
main :: IO ()
main = print ann
---- End of Main.hs
Also there is another bug in reifying the Orphan Annotations.
In the above example Main.hs depends on Ann.hs which defines Annotation for
`id`
When Main.hs compiles fine in the first go, its is able to retrieve the
annotation for `id`
Instead, if Ann.hs compiled successfully and Main.hs failed to compile and
when you later fix the Main.hs error, it is not able to retrieve that
annotation without recompiling Ann.hs
Regards,
Magesh B
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