[commit: base] master: Minor: replace undefined uses with error as mentioned in ticket #5532 (29ae842)

[Ian Lynagh]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/29ae84206a18c155183848932a32d771006f6335

>---------------------------------------------------------------

commit 29ae84206a18c155183848932a32d771006f6335
Author: Ryan Newton <rrnewton at gmail.com>
Date:   Thu Oct 6 14:52:59 2011 -0400

    Minor: replace undefined uses with error as mentioned in ticket #5532

>---------------------------------------------------------------

 Text/Printf.hs |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Text/Printf.hs b/Text/Printf.hs
index 021f670..0ef9364 100644
--- a/Text/Printf.hs
+++ b/Text/Printf.hs
@@ -111,12 +111,12 @@ instance (IsChar c) => PrintfType [c] where
 instance PrintfType (IO a) where
     spr fmts args = do
 	putStr (uprintf fmts (reverse args))
-	return undefined
+	return (error "PrintfType (IO a): result should not be used.")
 
 instance HPrintfType (IO a) where
     hspr hdl fmts args = do
 	hPutStr hdl (uprintf fmts (reverse args))
-	return undefined
+	return (error "HPrintfType (IO a): result should not be used.")
 
 instance (PrintfArg a, PrintfType r) => PrintfType (a -> r) where
     spr fmts args = \ a -> spr fmts (toUPrintf a : args)