126 lines
2.1 KiB
Markdown
126 lines
2.1 KiB
Markdown
![]() |
1、
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```rust
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struct DoubleRef<'a,'b:'a, T> {
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r: &'a T,
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s: &'b T
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}
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fn main() {
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println!("Success!")
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}
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```
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2、
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```rust
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struct ImportantExcerpt<'a> {
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part: &'a str,
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}
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impl<'a: 'b, 'b> ImportantExcerpt<'a> {
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fn announce_and_return_part(&'a self, announcement: &'b str) -> &'b str {
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println!("Attention please: {}", announcement);
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self.part
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}
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}
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fn main() {
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println!("Success!")
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}
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```
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3、
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```rust
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fn f<'a, 'b>(x: &'a i32, mut y: &'b i32) where 'a: 'b {
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y = x; // &'a i32 is a subtype of &'b i32 because 'a: 'b
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let r: &'b &'a i32 = &&0; // &'b &'a i32 is well formed because 'a: 'b
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}
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fn main() {
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println!("Success!")
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}
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```
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4、
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```rust
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fn call_on_ref_zero<F>(f: F) where for<'a> F: Fn(&'a i32) {
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let zero = 0;
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f(&zero);
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}
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fn main() {
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println!("Success!")
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}
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```
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Higher-ranked lifetimes may also be specified just before the trait: the only difference is the scope of the lifetime parameter, which extends only to the end of the following trait instead of the whole bound. This function is equivalent to the last one.
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```rust
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fn call_on_ref_zero<F>(f: F) where F: for<'a> Fn(&'a i32) {
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let zero = 0;
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f(&zero);
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}
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```
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5、
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```rust
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fn main() {
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let mut data = 10;
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let ref1 = &mut data;
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let ref2 = &mut *ref1;
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*ref2 += 2;
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*ref1 += 1;
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println!("{}", data);
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}
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```
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6、
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```rust
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struct Interface<'b, 'a: 'b> {
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manager: &'b mut Manager<'a>
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}
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impl<'b, 'a: 'b> Interface<'b, 'a> {
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pub fn noop(self) {
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println!("interface consumed");
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}
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}
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struct Manager<'a> {
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text: &'a str
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}
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struct List<'a> {
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manager: Manager<'a>,
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}
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impl<'a> List<'a> {
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pub fn get_interface<'b>(&'b mut self) -> Interface<'b, 'a>
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where 'a: 'b {
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Interface {
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manager: &mut self.manager
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}
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}
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}
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fn main() {
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let mut list = List {
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manager: Manager {
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text: "hello"
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}
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};
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list.get_interface().noop();
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println!("Interface should be dropped here and the borrow released");
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use_list(&list);
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}
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fn use_list(list: &List) {
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println!("{}", list.manager.text);
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}
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```
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