[GHC] #10385: Annotation restriction is not respected while generating Annotation via TH

[GHC]

#10385: Annotation restriction is not respected while generating Annotation via TH
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              Reporter:  simonpj     |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.1
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |        Blocked By:
             Test Case:              |   Related Tickets:
              Blocking:              |
Differential Revisions:              |
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 Magesh B [https://mail.haskell.org/pipermail/ghc-devs/2015-May/008910.html
 writes]:
 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`

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10385>
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