For those that don't know, Rust's regex crate descends from RE2 and Go's regexp library, both of which were written by Russ Cox, the author of the OP.
The principle difference between Rust's regex crate and, say, RE2 is its focus on literal optimizations. This speeds up a very large number of regexes, and it is one of the reasons why it does tend to be quite fast.
How good is ecosystem/crate support for more complex regex features? Speed is good, especially when you need it, but man, positive/negative lookahead/lookbehind and other advanced features are pretty damn wonderful once you know how to use them. The ability to choose what you want when you want it would be nice.
The regex crate doesn't support it, and it's not something I'm personally interested in working on. My goal at this point is to make the regex crate as good as possible at what it does, across the board. There's still a long way to go.
Other than that though, there is a WIP crate that actually builds on the `regex` crate and provides fancier features: https://crates.io/crates/fancy-regex (Created by the same author as Xi.)
There are also bindings to PCRE, but they are of varying quality. The regex crate's benchmark suite binds to several other libraries (including C++ and D libraries), but they are very minimal bindings sufficient for rough microbenchmarking: https://github.com/rust-lang/regex/tree/master/bench/src/ffi
Thanks. The info on the other crates is what I was looking for, I wouldn't expect this one to do more than what it aims for, which seems to be a specific type of regex engine which isn't amenable to all features but gets extra speed in that trade-off.
The principle difference between Rust's regex crate and, say, RE2 is its focus on literal optimizations. This speeds up a very large number of regexes, and it is one of the reasons why it does tend to be quite fast.