[Animats]

It's syntactic sugar for try/catch blocks. No new functionality.

Try/catch and exceptions seem to be tough for programmers to handle. You have to have disciplined unwinding for exception propagation to work well when an unwind goes through multiple calls.

Rust's rather simple "?" operator, which I once thought was underpowered, seems to be a workable solution. It's just syntactic sugar for return on error, but because there's a standard error trait, that usually works out well.

The lesson from this is to get your error objects right early in the history of a language, because you can't retrofit them. Once you have that right, how to report errors becomes sane, and the mechanism becomes less important.