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39 lines
903 B
39 lines
903 B
一些lifetime消除规则
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### 1
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Let's talk about a feature that's available in both editions: we've added some additional elision rules for `impl` blocks and function definitions. Code like this:
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```rust
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impl<'a> Reader for BufReader<'a> {
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// methods go here
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}
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```
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can now be written like this:
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```rust
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impl Reader for BufReader<'_> {
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// methods go here
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}
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```
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The `'_` lifetime still shows that `BufReader` takes a parameter, but we don't need to create a name for it anymore.
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### 2
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Lifetimes are still required to be defined in structs. However, we no longer require as much boilerplate as before:
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```rust
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// Rust 2015
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struct Ref<'a, T: 'a> {
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field: &'a T
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}
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// Rust 2018
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struct Ref<'a, T> {
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field: &'a T
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}
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```
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The `: 'a` is inferred. You can still be explicit if you prefer. We're considering some more options for elision here in the future, but have no concrete plans yet.
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