[GHC] #11051: GHCi with +t option set shows type representations

[GHC]

#11051: GHCi with +t option set shows type representations
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 My guess is that we'd want to do something like this to ensure that
 `System` names never make it to the user.
 {{{#!patch
 diff --git a/compiler/main/InteractiveEval.hs
 b/compiler/main/InteractiveEval.hs
 index 013be3c..d3020d7 100644
 --- a/compiler/main/InteractiveEval.hs
 +++ b/compiler/main/InteractiveEval.hs
 @@ -235,8 +235,9 @@ runStmtWithLocation source linenumber expr step = do
  runDecls :: GhcMonad m => String -> m [Name]
  runDecls = runDeclsWithLocation "<interactive>" 1

 -runDeclsWithLocation
 - :: GhcMonad m => String -> Int -> String -> m [Name]
 +-- | Run some declarations and return any user-visible names that were
 brought
 +-- into scope.
 +runDeclsWithLocation :: GhcMonad m => String -> Int -> String -> m [Name]
  runDeclsWithLocation source linenumber expr =
    do
      hsc_env <- getSession
 @@ -246,7 +247,13 @@ runDeclsWithLocation source linenumber expr =
      hsc_env <- getSession
      hsc_env' <- liftIO $ rttiEnvironment hsc_env
      modifySession (\_ -> hsc_env')
 -    return (map getName tyThings)
 +
 +    -- Trac #11051: We filter out system names since the user is not
 interested
 +    -- in them. These include,
 +    --   * Data family tycons from, e.g., derived Generic instances
 +    --   * Type representation (Typeable) definitions (e.g. $trMyModule)
 +    --   * others
 +    return $ filter (not . isSystemName) $ map getName tyThings
 }}}

 With this we've reduced the problem to ensuring that the generated
 Typeable identifiers get marked as `System` names. Currently they are
 conjured by up `IfaceEnv.newGlobalBinder` which only knows how to produce
 `External` names.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11051#comment:5>
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