#3621: "No match in record selector Var.tcTyVarDetails" with incorrect multi-
parameter newtype derivation
-----------------------------+----------------------------------------------
Reporter: pwb | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.10.4 | Severity: minor
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
-----------------------------+----------------------------------------------
{{{
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
import Control.Monad.State
newtype WrappedState s a = WS { runWS :: State s a }
deriving (Monad, MonadState state)
}}}
Note that the 'deriving' for {{{MonadState}}} has the wrong variable name.
It should be rejected with something like "not in scope: type variable
'state'" but instead this happens:
{{{
[pwb at rhuidean tmp]$ ghc bug.hs
ghc: panic! (the 'impossible' happened)
(GHC version 6.10.4 for x86_64-unknown-linux):
No match in record selector Var.tcTyVarDetails
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3621>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler