-> readIface iface_path `thenRn` \ read_result ->
case read_result of
Left err -> -- Old interface file not found, or garbled; give up
- traceRn (text "Bad old interface file" $$ nest 4 err) `thenRn_`
+ traceHiDiffsRn (
+ text "Cannot read old interface file:"
+ $$ nest 4 err) `thenRn_`
returnRn (outOfDate, Nothing)
Right parsed_iface