[Pkg-haskell-maintainers] Bug#635113: Generated code fails to compile: uses bang patterns without corresponding {-# LANGUAGE BangPatterns #-} pragma

Erik de Castro Lopo erikd at mega-nerd.com
Fri Jul 22 22:37:56 UTC 2011

Josh Triplett wrote:

> Package: alex
> Version: 2.3.5-2
> Severity: grave
> The fix for bug 623067 makes alex -g use bang patterns, but doesn't add
> the corresponding BangPatterns extension to the list of extensions in
> the LANGUAGE pragma at the top of the file.  This makes the generated
> code fail to compile:
> dist/build/apters/apters-tmp/Scanner.hs:294:18:
>     Illegal bang-pattern (use -XBangPatterns):
>     ! (base)

Any idea which file is it that is missing this pragma? I've just
looked at the patch (which I generated) and it does add the pragma
to alex-2.3.5/src/Scan.x.

    --- alex-2.3.5.orig/src/Scan.x
    +++ alex-2.3.5/src/Scan.x
    @@ -11,7 +11,7 @@
    -{-# OPTIONS_GHC -w #-}
    +{-# OPTIONS_GHC -w -XBangPatterns #-}
     module Scan(lexer, AlexPosn(..), Token(..), Tkn(..), tokPosn) where

I'm quite a regular user of alex and I'm surprised I haven't run
into this yet.

Erik de Castro Lopo

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