Rust originally supported only M:N green threads. Native thread support was added, became the default, and green thread support was eventually moved out of Rust

Rust originally supported only M:N green threads. Native thread support was added, became the default, and green thread support was eventually moved out of Rust core to a library. Here is the proposal and rationale: https://github.com/rust-lang/rfcs/blob/0806be4f282144cfcd55b1d20284b43f87cbe1c6/text/0230-remove-runtime.md https://github.com/rust-lang/rfcs/blob/0806be4f282144cfcd55b...