hub.darcs.net :: jcpetruzza -> hint -> issue

#3Can't interpret values of types that, in the interpreter, are in scope but only qualified

remdezx

I wrote following code using qualified imports (setImportsQ) but it seems not work. Am I doing something wrong or is it a bug in the library?

Code:

module Main where

import           Data.Map                     (Map)
import qualified Language.Haskell.Interpreter as I



run :: I.Interpreter ()
run = do 
    I.reset
    I.setImportsQ [("Prelude"   , Nothing)
                  ,("Data.Map"  , Just "Map")]
    _ <- I.interpret "Map.empty" (I.as :: Map Int Int)
    return ()


main :: IO ()
main = I.runInterpreter run >>= print

Output:

Left (WontCompile [GhcError {errMsg = "Not in scope: type constructor or class `Map'\nPerhaps you meant `Map.Map' (imported from Data.Map)"}])

• remdezxTue Jun 17 13:11:39 UTC 2014
  • description updated
• remdezxTue Jun 17 13:11:54 UTC 2014
  • description updated
• jcpetruzzaTue Aug 19 09:17:22 UTC 2014

  Interesting. The problem is that to ensure that the expression to interpret has the right type, we add a type annotation using the Typeable instance of the target type.

  In this case, the actual string becomes something like "(Map.empty) :: Map Int Int" and the problem is that "Map Int Int" is not in scope in the interpreter.

  Since base-4.4.0.0, we can also get the defining module for each type using the Typeable interface. That means that in principle we could go from Map Int Int to, say, "Data.Map.Base.Map GHC.Types.Int GHC.Types.Int", and then we would need to enforce behind the scenes that those modules are imported qualified as well every time.

• jcpetruzzaTue Aug 19 09:19:48 UTC 2014
  • summary changed to "Can't interpret values of types that, in the interpreter, are in scope but only qualified"
  • added tag bug
• Hiromi ISHIISat Aug 22 13:52:59 UTC 2015

  I think I resolve this issue by this patch: http://hub.darcs.net/konn/hint/patch/475c3c169050c7c1594389afada18e4395903ced . I confirmed that this passes unit-tests. Can you merge this change?

• mvdanWed Mar 9 16:32:41 UTC 2016

  hint is now on GitHub, feel free to open this issue over there or open pull requests with patches:

  https://github.com/mvdan/hint