private CompletionFailure newCompletionFailure(TypeSymbol c,
                                                       JCDiagnostic diag) {
            if (!cacheCompletionFailure) {
                // log.warning("proc.messager",
                //             Log.getLocalizedString("class.file.not.found", c.flatname));
                // c.debug.printStackTrace();
                return new CompletionFailure(c, diag);
            } else {
                CompletionFailure result = cachedCompletionFailure;
                result.sym = c;
                result.diag = diag;
                return result;
            }
        }