Mutex::lock得到的可变借用似乎不具备子域可变性可分割的性质

use std::sync::Mutex; struct N { a: i32, b: i32, } fn main() { let mut n = N { a: 0, b: 0 }; let a = &n.a; let b = &mut n.b; println!("{a} {b}");// 编译正常 //...