Not sure how much this helps, but in Rust "!" usually means "this name refers to a macro" and "?" usually means "if the value of this expression is an error, sh

Not sure how much this helps, but in Rust "!" usually means "this name refers to a macro" and "?" usually means "if the value of this expression is an error, short-circuit the current function by returning that error." Usually when you're reading working code, you can ignore those two symbols and still get the meaning. (Those symbols also have some more advanced meanings for when you're dealing with generic/templated types, but those are pretty rare and unlikely to show up in examples.)