#7175: Panic when wrongly using a type family as return types for GADTs
--------------------------------+-------------------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.6.1-rc1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Compile-time crash | Testcase:
Blockedby: | Blocking:
Related: |
--------------------------------+-------------------------------------------
The following code causes the following panic:
{{{
{-# LANGUAGE TypeFamilies, GADTs #-}
type family F a
data G1 a where
G1C :: F Int
data G2 a where
G2C :: F Int
}}}
{{{
ghc: panic! (the 'impossible' happened)
(GHC version 7.6.0.20120810 for x86_64-apple-darwin):
compiler/typecheck/TcTyClsDecls.lhs:1081:5-62: Irrefutable pattern
failed for pattern Data.Maybe.Just subst
}}}
Admittedly, the code causing the panic is silly, but it happened to me as
I was refactoring. Having two separate GADTs with the wrong return types
seems necessary to cause the panic.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7175>
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
