bug-tvar-passed-renamer.hs

{-# LANGUAGE GADTs, ScopedTypeVariables #-}
module Main where

import           Prelude          (Either(..), Bool, Int, flip, undefined)

import           Data.Typeable

import           Control.Concurrent.MVar

-- Bug

bug :: WrappedR Int -> SomeFunction
bug (Wrap node) = case node of
  (Memo' (emptyT :: t a b) (memoize :: MVar (t a b) -> (a -> b) -> a -> b) (Var m :: R' a b Int) :: R' a b Int) -> -- breaks
  --(Memo' (emptyT :: t a b) memoize (Var m) :: R' a b Int) -> -- also breaks
  --(Memo' emptyT memoize (Var m) :: R' a b Int) -> -- Compiles
    undefined

-- Data definitions
data R' a b r where
  Memo'    :: (Typeable a, Typeable b)
           =>  t a b -> (MVar (t a b) -> (a -> b) -> a -> b)
           -> R' a b r -> R' a b r
  Var      :: (Typeable a, Typeable b)
           => r -> R' a b r

data SomeFunction where
  SomeFunction :: (a -> b) -> SomeFunction

data WrappedR r where
  Wrap :: (Typeable a, Typeable b) => R' a b r -> WrappedR r

error.txt

[1 of 1] Compiling Main             ( /Users/alessandro/Documents/Uni/thesis/test/bug-tvar-passed-renamer.hs, interpreted )

/Users/alessandro/Documents/Uni/thesis/test/bug-tvar-passed-renamer.hs:14:104:
    GHC internal error: `a' is not in scope during type checking, but it passed the renamer
    tcl_env of environment: [(awz,
                              Identifier[node::R' a b Int, <NotTopLevel>, 1]),
                             (rg7,
                              Identifier[bug::WrappedR Int -> SomeFunction, <NotTopLevel>, 1])]
    In the type `R' a b Int'
    In a pattern type signature: R' a b Int
    In the pattern:
      Memo' (emptyT :: t a b)
            (memoize :: MVar (t a b) -> (a -> b) -> a -> b)
            (Var m :: R' a b Int) :: R' a b Int
Failed, modules loaded: none.