chinese https://github.com/sunface/rust-by-practice/blob/e0e88e963a3d2c96029e1e3dca3397d38db78cab/zh-CN/book.toml#L22 English https://github.com/sunface/rust-by-practice/blob/e0e88e963a3d2c96029e1e3dca3397d38db78cab/en/book.toml#L22 Rust play ground version is already 2021 on English pages. Chinese version should have the same version. And, some solutions don't work under 2018, e.g. [this](https://github.com/sunface/rust-by-practice/issues/500).
chinese
rust-by-practice/zh-CN/book.toml
Line 22 in e0e88e9
English
rust-by-practice/en/book.toml
Line 22 in e0e88e9
Rust play ground version is already 2021 on English pages. Chinese version should have the same version.
And, some solutions don't work under 2018, e.g. this.