Default Cargo feature resolver

Summary

Details

Since Rust 1.51.0, Cargo has opt-in support for a new feature resolver which can be activated with resolver = "2" in Cargo.toml.

Starting in Rust 2021, this will be the default. That is, writing edition = "2021" in Cargo.toml will imply resolver = "2".

The new feature resolver no longer merges all requested features for crates that are depended on in multiple ways. See the announcement of Rust 1.51 for details.