bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

documentation fix

Browse source
This commit is contained in:
Ding Xiang Fei 2020-08-06 15:36:57 +08:00
parent d65c08e9cc
commit f9ccd39ae3
No known key found for this signature in database
GPG key ID: 3CD748647EEF6359
2 changed files with 10 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

10
compiler/rustc_middle/src/middle/region.rs
View file

@ -283,23 +283,27 @@ pub struct ScopeTree {
/// To see that this method works, consider:
///
/// Let `D` be our binding/temporary and `U` be our other HIR node, with
/// `HIR-postorder(U) < HIR-postorder(D)` (in our example, U would be
/// the yield and D would be one of the calls). Let's show that
/// `D` is storage-dead at `U`.
/// `HIR-postorder(U) < HIR-postorder(D)`. Suppose, as in our example,
/// U is the yield and D is one of the calls.
/// Let's show that `D` is storage-dead at `U`.
///
/// Remember that storage-live/storage-dead refers to the state of
/// the *storage*, and does not consider moves/drop flags.
///
/// Then:
///
/// 1. From the ordering guarantee of HIR visitors (see
/// `rustc_hir::intravisit`), `D` does not dominate `U`.
///
/// 2. Therefore, `D` is *potentially* storage-dead at `U` (because
/// we might visit `U` without ever getting to `D`).
///
/// 3. However, we guarantee that at each HIR point, each
/// binding/temporary is always either always storage-live
/// or always storage-dead. This is what is being guaranteed
/// by `terminating_scopes` including all blocks where the
/// count of executions is not guaranteed.
///
/// 4. By `2.` and `3.`, `D` is *statically* storage-dead at `U`,
/// QED.
///