panic with GeneralizedNewtypeDeriving and a .hs-boot file

[igloo]

With A.hs-boot:

module A where

data A
    deriving Show

We can get a panic:

$ ghc -c -XGeneralizedNewtypeDeriving A.hs-boot

A.hs-boot:5:13:ghc: panic! (the 'impossible' happened)
  (GHC version 6.9.20080716 for x86_64-unknown-linux):
        newTyConEtadRhs main:A.A{tc r6K}

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

[simonpj]

Good bug. As the user manual says, you can't put deriving clauses in hs-boot files. I've made GHC check properly for this now.

Tue Aug  5 11:54:02 BST 2008  simonpj@microsoft.com
  * Fix Trac #2449
  
  Deriving isn't allowed in hs-boot files (says the user manual)
  This patch checks properly instead of crashing!

IAN: I'm not sure how to add a test case whose source file is a hs-boot file. Could you do so please? The one above will do fine. Thanks. Then close.

Simon

[igloo]

Test drvfail016 added