Exchange: a deterministic order book and matching engine in Rust

Hi! I'd like feedback on exchange, a limit order book and matching engine in Rust: orders go in, trades and an event stream come out. Repo: GitHub - Wandalen/exchange · GitHub The problem A matching engine is easy to get almost right. The hard part is what must never happen: Spending money you don't have: a buy order rests on the book before its funds are actually held. Money appearing or vanishing: a trade where the buyer's payment and the seller's proceeds don't match to the last cent. A d...