We applied for my wife's settlement visa from Shanghai,too - back in 2016. Our first application was rejected (missing supporting docs) but the second application 3 months later was successful. Both took around 3 weeks. Visa processing times in China are quite quick - according to
this, 79% of settlement visa applications in February in Beijing were processed within 10 days (I couldn't find figures for Shanghai).
With our rejected application, I knew straight away that it hadn't been successful because they refunded the IHS fee back to my credit card the day after they informed us that a decision had been made. So you could check your bank/credit card account for the refund, though this isn't a reliable indicator since it could take up to six weeks for them to refund the IHS fee [
source].