v0.8.5 Compiling guessing_game v0.1.0 (file:///projects/guessing_game) error[E0308]: mismatched types --> src/main.rs:23:21 | 23 | match guess.cmp(&secret_number) { | --- ^^^^^^^^^^^^^^ compile `guessing_game` (bin "guessing_game") due to 1 previous error 错误的核心表明这里有 不匹配的类型（mismatched types）。Rust 有一个静态强类型系统，同 时也有类型推断。当我们写出 let guess = String::new() 时，Rust 推断出 guess 应该是 String 类型，并不需要我们 $ cargo run Compiling variables v0.1.0 (file:///projects/variables) error[E0308]: mismatched types --> src/main.rs:3:14 | 2 | let mut spaces = " "; | ----- expected