Can you use Sun Disk to give Rush to a unit drawn from Promising Future by tapping Sun Disk while Promising Future is resolving?

Ruling: No, you cannot tap Sun Disk while Promising Future is resolving because Sun Disk doesn't have Reaction, which means it cannot be used while a chain is open or while anything is resolving.

Sequence: (for a legal way to give Rush to a unit from Promising Future)

• Have Sun Disk already in play from a previous turn
• Play a unit that grants Legion (e.g., a 2-cost unit)
• Tap Sun Disk while you have Legion
• Play Promising Future
• The next unit from Promising Future will come in readied

Nuances:

• Sun Disk can only be used when no chain is open and nothing is resolving
• You need to activate Sun Disk before playing Promising Future, not during its resolution