From a0d1b8a97af94e15783fee2ebbf46c69ac881a0f Mon Sep 17 00:00:00 2001
From: Simon Marlow <marlowsd@gmail.com>
Date: Wed, 10 Aug 2011 09:10:24 +0100
Subject: [PATCH] Fail configure if Alex 3 is found.  Haddock doesn't build
 with Alex 3 yet, and fixing it is non-trivial (a change to Cabal is needed). 
 So I'm making configure fail with an error suggesting to install an older
 Alex for now.

---
 configure.ac | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/configure.ac b/configure.ac
index 29185d3ca387..f2aba416ecdc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -608,6 +608,9 @@ dnl ** check for installed alex binary + version
 dnl    (don't do it if we're booting from .hc files though.)
 if test "$BootingFromHc" = "NO"; then
 FPTOOLS_ALEX
+if test "${Alex3}" = "YES"; then
+  AC_MSG_ERROR([GHC does not build with Alex 3 yet; please install an older version (we hope to fix this soon).])
+fi
 fi;
 
 dnl --------------------------------------------------