打破长字符串文字

使用\字符打破常规字符串文字

let a = "foobar";
let b = "foo\
         bar";

// `a` and `b` are equal.
assert_eq!(a,b);

将原始字符串文字分隔为单独的字符串，并将它们与 concat! 宏连接起来

let c = r"foo\bar";
let d = concat!(r"foo\", r"bar");

// `c` and `d` are equal.
assert_eq!(c, d);