> what happens when there is an error reading the file?
the question mark `?` denotes the fact that the error is bubbled up (kind of like an exception, but with stronger typing and less silent)
the question mark `?` denotes the fact that the error is bubbled up (kind of like an exception, but with stronger typing and less silent)
If Try::branch gives us a ControlFlow::Break we're done here, return immediately with the value wrapped by Break [if any] inside an Err, otherwise we have ControlFlow::Continue wrapping a value we can use to continue with execution of this function.
This is type checked, so if the function says it returns Result<Goose, Dalek> then the type of the value wrapped in a ControlFlow::Break had better be Err(Dalek) or else we can't use our ? operator here.
Reifying ControlFlow here separates concerns properly - if we want to stop early successfully then control flow can represent that idea just fine whereas an Exception model ties early exit to failure.
I think the blog post is not focussing on error handling too much, but in any case this is 'safe', just could likely be handled better in a real-world case.