From the Player's Handbook (p. 202) under
Casting Time > Bonus Action,
A spell cast with a bonus action is especially swift. You must use a bonus action on your turn, provided that you haven't already taken a bonus action this turn. You can't cast another spell during the same turn, except for a cantrip with a casting time of one action.
meaning that once a bonus-action-spell is cast, following that one cannot cannot cast another non-cantrip spell as an action. However, the wording above does not seem to preclude the use of a non-cantrip spell as an action BEFORE using your bonus action to cast a bonus-action spell.
Is there anywhere else in the PHB where it is clarified whether the order matters or not? In the absence of further ruling, should we accept the literal meaning above which says "cannot cast a non-cantrip spell AFTER a bonus-action spell"?