Answers to What are the differences between Rust's `String` and `str`? describe how &str and String relate to each other.
令人惊讶的是，str比固定大小的数组更有限，因为它不能声明为局部变量.汇编
let arr_owned = [0u8; 32];
let arr_slice = &arr_owned;
let str_slice = "apple";
let str_owned = *str_slice;
在Rust 1.32.0中，我得到
error[E0277]: the size for values of type `str` cannot be known at compilation time
--> src/lib.rs:6:9
这让人困惑，因为编译器可以知道"apple"的大小，但它不是str类型的一部分.
Is there a linguistic reason for the asymmetry between Vec<T> <-> [T; N] and String <-> str owned types? Could an str[N] type, which would be a shortand to a [u8; N] that only contains provably valid UTF-8 encoded strings, replace str without breaking lots of existing code?