Translation: "You screwed up somewhere in this entire file. Figure it out yourself. Good luck! šŸ¤·ā€

It's the "Segmentation faultā€ of the modern era.

i’m unable to type-check YOUR expression in reasonable time
(The actual problem, 67 lines below the error message: .disabled() needs to be applied to the Button, not the ToolbarItem, which I had to figure out by just commenting out random stuff until it compiled.)
@marcoarment sadly, that seems to be the only way to debug the error. I’ve had to do that too many times to count.