Rust does not have three error systems. It has one: the Error trait. io::Error is one of many that implement it (nothing special about it). Errors defined via thiserror also implement it.

“Anyhow” just allows you to conveniently say “some Error” if you don’t care to write out an API contract specifying types of errors your function might spit out.

▲

tptacek an hour ago | parent [-]

He's not making that up; in practice, you're going to run into and need to make mental space for the idiosyncrasies of multiple error frameworks.

▲

dwattttt an hour ago | parent [-]

I guess you might have to if you need to use a library someone's written that doesn't implement the standard.

Writing primarily applications, I couldn't tell you what error handling frameworks my dependencies are using: I literally don't know, and haven't needed to know in order to display, fail, or succeed.

EDIT to add: I use anyhow for this, so I should also add "add context to an error when I fall" to the list of things I do.

	▲	the__alchemist 5 minutes ago \| parent [-]
		What's the standard? I'm not being snarky; I'm going down the thought process of how this would work in practice. I am on team Io Error [on std rust]", somewhat arbitrarily. If I call a lib that is on Team Anyhow, or Team Custom Error Enum, I will have to do some (Straightfoward, but a little clumsy) conversions if I want ? to work. This is complicated by being able to impl From<ErrorType1> for ErrorType2 only in one direction if you don't control the other crate. (due to the orphan rule)