Expects a document whose root is a ‘GrandWrapper’ carrying structured Handle children whose boolean used attrs were added by writerly_handles_grand_wrapper_substitute.

Emits one DesugaringWarning per handle whose used attr is false and whose id points to a node whose tag is listed in the param, blamed on that node. (Passing [“MathBlock”] therefore reports unused equation handles.)

Handles on nodes of any other tag are silently ignored, as are ids that no node carries.

Leaves the tree unchanged; must run before the GrandWrapper is unwrapped.