Another wibble to the head-exploded error message (suggested by David Roundy)

compiler/typecheck/TcPat.lhs

@@ -920,7 +920,7 @@ patCtxt pat 	    = Just (hang (ptext SLIT("In the pattern:"))
 existentialExplode pat
   = hang (vcat [text "My brain just exploded.",
 	        text "I can't handle pattern bindings for existentially-quantified constructors.",
-	        text "Instead, use a case-expression to unpack the constructor.",
+	        text "Instead, use a case-expression, or do-notation, to unpack the constructor.",
 		text "In the binding group for"])
 	4 (ppr pat)