Swift Quiver takes a bonus action to cast, then it lets you use a bonus action to make two attacks. So the turn you cast it, you use your bonus action just to cast it, then you need another bonus action to use it's ability to make two attacks, right?
The description of the Swift Quiver spell says (PHB, p. 279):
You transmute your quiver so it produces an endless supply of nonmagical ammunition, which seems to leap into your hand when you reach for it.
On each of your turns until the spell ends, you can use a bonus action to make two attacks with a weapon that uses ammunition from the quiver. Each time you make such a ranged attack, your quiver magically replaces the piece of ammunition you used with a similar piece of nonmagical ammunition. […]
Does Swift Quiver let you make 2 extra attacks with a bonus action on the same turn you cast it?
Best Answer
You can only take one bonus action per turn.
The rules for bonus actions state:
Since you used your bonus action to cast swift quiver, you cannot use your bonus action to make the two attacks this turn.
Compare this to the spell expeditious retreat (emphasis mine):
This spell (which has a casting time of "1 bonus action") allows you to immediately take the Dash action, and on subsequent turns, use your bonus action to do so.