From 222589a9f270d90f4ac21bf22b0a82e8ae126718 Mon Sep 17 00:00:00 2001
From: Simon Marlow <marlowsd@gmail.com>
Date: Sat, 17 Sep 2011 13:06:36 +0100
Subject: fix bug in :show bindings when a variable is bound to an exception

---
 compiler/ghci/Debugger.hs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

(limited to 'compiler/ghci/Debugger.hs')

diff --git a/compiler/ghci/Debugger.hs b/compiler/ghci/Debugger.hs
index e859609527..c8946d6367 100644
--- a/compiler/ghci/Debugger.hs
+++ b/compiler/ghci/Debugger.hs
@@ -27,6 +27,7 @@ import GHC
 import Outputable
 import PprTyThing
 import MonadUtils
+import Exception
 
 import Control.Monad
 import Data.List
@@ -209,8 +210,13 @@ pprTypeAndContents id = do
   if pcontents 
     then do
       let depthBound = 100
-      term      <- GHC.obtainTermFromId depthBound False id
-      docs_term <- showTerm term
+      -- If the value is an exception, make sure we catch it and
+      -- show the exception, rather than propagating the exception out.
+      e_term <- gtry $ GHC.obtainTermFromId depthBound False id
+      docs_term <- case e_term of
+                      Right term -> showTerm term
+                      Left  exn  -> return (text "*** Exception:" <+>
+                                            text (show (exn :: SomeException)))
       return $ pprdId <+> equals <+> docs_term
     else return pprdId
 
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