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Update the unstable book regarding [e; dyn n].

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This commit is contained in:
Masaki Hara 2018-07-12 20:26:13 +09:00
parent c72e87e30a
commit 438edc3d5e
1 changed files with 3 additions and 3 deletions
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6
src/doc/unstable-book/src/language-features/unsized-locals.md
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@ -127,13 +127,13 @@ One of the objectives of this feature is to allow `Box<dyn FnOnce>`, instead of
## Variable length arrays
The RFC also describes an extension to the array literal syntax `[e; n]`: you'll be able to specify non-const `n` to allocate variable length arrays on the stack.
The RFC also describes an extension to the array literal syntax: `[e; dyn n]`. In the syntax, `n` isn't necessarily a constant expression. The array is dynamically allocated on the stack and has the type of `[T]`, instead of `[T; n]`.
```rust,ignore
#![feature(unsized_locals)]
fn mergesort<T: Ord>(a: &mut [T]) {
let mut tmp = [T; a.len()];
let mut tmp = [T; dyn a.len()];
// ...
}
@ -144,7 +144,7 @@ fn main() {
}
```
VLAs are not implemented yet.
VLAs are not implemented yet. The syntax isn't final, either. We may need an alternative syntax for Rust 2015 because, in Rust 2015, expressions like `[e; dyn(1)]` would be ambiguous. One possible alternative proposed in the RFC is `[e; n]`: if `n` captures one or more local variables, then it is considered as `[e; dyn n]`.
## Advisory on stack usage