I don’t do Rust but that was nicely readable. One comment: using Enums for stock symbols presumably forces a recompile on each new symbol. What would be the idiomatic representation in Rust for things like that? Some kind of interned string?
A string works. If a numerical/in-place representation is wanted for efficiency, you could rely on the fact that stock symbols are always less than 8 characters, so we can parse it into an array of 8 bytes.
