X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=compiler%2Fspecialise%2FRules.lhs;h=2798ca13eb6e9cfe7c61a321acb452b228304957;hb=8d4bb83f1c3c6abb12e3ae1204034149349f047d;hp=6fc35a515b03d99eb8001d37a9ba4dcb93fa3ec4;hpb=29723ae3cdf941a9647d2cd67e5aa15bab8f4e22;p=ghc-hetmet.git

diff --git a/compiler/specialise/Rules.lhs b/compiler/specialise/Rules.lhs
index 6fc35a5..2798ca1 100644
--- a/compiler/specialise/Rules.lhs
+++ b/compiler/specialise/Rules.lhs
@@ -348,19 +348,25 @@ matchN in_scope tmpl_vars tmpl_es target_es
 				Just e -> e
 				other  -> unbound tmpl_var'
  
-    unbound var = pprPanic "Template variable unbound in rewrite rule" (ppr var)
+    unbound var = pprPanic "Template variable unbound in rewrite rule" 
+			(ppr var $$ ppr tmpl_vars $$ ppr tmpl_vars' $$ ppr tmpl_es $$ ppr target_es)
 \end{code}
 
 Note [Template binders]
 ~~~~~~~~~~~~~~~~~~~~~~~
 Consider the following match:
 	Template:  forall x.  f x 
-	Taret:     f (x+1)
-This should succeed, because the template variable 'x' has nothing to do with
-the 'x' in the target.
+	Target:     f (x+1)
+This should succeed, because the template variable 'x' has 
+nothing to do with the 'x' in the target. 
 
-To achive this, we use rnBndrL to rename the template variables if necessary;
-the renamed ones are the tmpl_vars'
+On reflection, this case probably does just work, but this might not
+	Template:  forall x. f (\x.x) 
+	Target:    f (\y.y)
+Here we want to clone when we find the \x, but to know that x must be in scope
+
+To achive this, we use rnBndrL to rename the template variables if
+necessary; the renamed ones are the tmpl_vars'
 
 
 	---------------------------------------------