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I have following program:

{-# LANGUAGE DataKinds, TypeFamilies, GADTs #-}
module Main where

data U = Unit

data SU (a :: U) where
  SInt :: SU Unit

type family I (a :: U) :: U
type instance I Unit = Unit

type SUI a = SU (I a)

main :: IO ()
main = return ()

This program compiles successfully, but won't recompile due to an internal error.

$ ghc WontCompile.hs
[1 of 1] Compiling Main             ( WontCompile.hs, WontCompile.o )
Linking WontCompile ...

$ ghc WontCompile.hs -fforce-recomp 
[1 of 1] Compiling Main             ( WontCompile.hs, WontCompile.o )

WontCompile.hs:12:18:
    GHC internal error: `I' is not in scope during type checking, but it passed the renamer
    tcl_env of environment: [(a9O, AThing k_a9X)]
    In the type `SU (I a)'
    In the type synonym declaration for `SUI'

Trac metadata

Trac field	Value
Version	7.4.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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