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Expliciting lifetime in the first example #351

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Expliciting lifetime in the first example #351

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Expliciting lifetime in the first example
Arthur-Milchior May 5, 2022
b33c4c8
Update src/lifetimes.md
Arthur-Milchior May 29, 2022
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28 changes: 16 additions & 12 deletions src/lifetimes.md
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Expand Up @@ -32,9 +32,10 @@ explicitly is *extremely noisy*. All Rust code relies on aggressive inference
and elision of "obvious" things.

One particularly interesting piece of sugar is that each `let` statement
implicitly introduces a scope. For the most part, this doesn't really matter.
However it does matter for variables that refer to each other. As a simple
example, let's completely desugar this simple piece of Rust code:
implicitly introduces a scope immediately after the declaration. For the most part,
this doesn't really matter. However it does matter for variables that refer to
each other. As a simple example, let's completely desugar this simple piece of
Rust code:

```rust
let x = 0;
Expand All @@ -47,21 +48,24 @@ likely desugar to the following:

<!-- ignore: desugared code -->
```rust,ignore
// NOTE: `'a: {` and `&'b x` is not valid syntax!
'a: {
// NOTE: `'global_lifetime: {` and `&'x_lifetime x` is not valid syntax!
'global_lifetime: {
let x: i32 = 0;
'b: {
// lifetime used is 'b because that's good enough.
let y: &'b i32 = &'b x;
'c: {
// ditto on 'c
let z: &'c &'b i32 = &'c y;
'x_lifetime: {
// lifetime used is 'x_lifetime because that's good enough.
let y: &'x_lifetime i32 = &'x_lifetime x;
'y_lifetime: {
// ditto on 'y_lifetime
let z: &'y_lifetime &'x_lifetime i32 = &'y_lifetime y;
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After some re-thinking of this, I still think this is too descriptive. We easily can find 'a is a lifetime and curly braces are scopes if we're familiar with Rust's syntax. That is, naming lifetimes looks redundant, and tweaking prior wording should be enough here.

}
}
}
```

Wow. That's... awful. Let's all take a moment to thank Rust for making this easier.
Wow. That's... awful. Let's all take a moment to thank Rust for making this
easier. To make matter worse, traditionally, lifetimes are not as descriptive
and simply called `'a`, `'b`, and so on. We will respect this tradition going
forward.
Comment on lines +65 to +68
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I don't think this change is much helpful for readers and worth rephrasing so. As stated in the intro, we assume readers have a basic knowledge of Rust, actually, https://doc.rust-lang.org/nightly/book/ch10-03-lifetime-syntax.html#lifetime-annotation-syntax explains it and that should be enough.


Actually passing references to outer scopes will cause Rust to infer
a larger lifetime:
Expand Down