#7006: Panic when promoted GADT arguments cross module boundaries
--------------------------------+-------------------------------------------
Reporter: anders_ | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.1 | Keywords: DataKinds
Os: MacOS X | Architecture: x86_64 (amd64)
Failure: Compile-time crash | Testcase:
Blockedby: | Blocking:
Related: |
--------------------------------+-------------------------------------------
This seems to only happen when the importing module is compiled in a
separate invocation of GHC from the module containing the GADT. That is,
it happens with `ghc -c`-ing the two separately, or with `--make`, when
only the importing module has been changed since last time. Cleaning
between each compile seems to be a workaround, but that’s a massive pain.
`:)`
Sample code & GHC's reaction:
{{{
{-# LANGUAGE KindSignatures, TypeOperators, DataKinds, GADTs #-}
module A where
data List (xs :: [*]) where
N :: List '[]
(:>) :: x -> List xs -> List (x ': xs)
}}}
{{{
{-# LANGUAGE GADTs, TypeOperators #-}
module B where
import A
foo :: List (x ': xs) -> x
foo (x :> _) = x
}}}
{{{
$ ghc -c A.hs
$ ghc -c B.hs
ghc: panic! (the 'impossible' happened)
(GHC version 7.4.1 for x86_64-apple-darwin):
tyThingTyCon Data constructor `ghc-prim:GHC.Types.:{(w) d 64}'
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
(As an aside, it’s kind of annoying that `TypeOperators` isn’t
automatically implied by `DataKinds`, but that’s not important really.)
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7006>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
