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tree: remove useless pinning of Tree object

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Since Tree is Unpin, Pin<Box<Tree>> can be moved and it's basically the same
as Box<Tree>. I heard using Box<T> still violates strict aliasing rule, but
Pin wouldn't give any additional guarantee.

https://morestina.net/blog/1868/self-referential-types-for-fun-and-profit
This commit is contained in:
Yuya Nishihara 2023-06-30 23:33:24 +09:00
parent 0eddf7c80d
commit da3c03206c
1 changed files with 6 additions and 7 deletions
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13
lib/src/tree.rs
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@ -17,7 +17,6 @@ use std::fmt::{Debug, Error, Formatter};
use std::hash::{Hash, Hasher}; use std::hash::{Hash, Hasher};
use std::io::Read; use std::io::Read;
use std::iter::Peekable; use std::iter::Peekable;
use std::pin::Pin;
use std::sync::Arc; use std::sync::Arc;
use itertools::Itertools; use itertools::Itertools;
@ -241,12 +240,12 @@ pub struct TreeEntriesIterator<'matcher> {
struct TreeEntriesDirItem { struct TreeEntriesDirItem {
entry_iterator: TreeEntriesNonRecursiveIterator<'static>, entry_iterator: TreeEntriesNonRecursiveIterator<'static>,
// On drop, tree must outlive entry_iterator // On drop, tree must outlive entry_iterator
tree: Pin<Box<Tree>>, tree: Box<Tree>,
} }
impl TreeEntriesDirItem { impl TreeEntriesDirItem {
fn new(tree: Tree) -> Self { fn new(tree: Tree) -> Self {
let tree = Box::pin(tree); let tree = Box::new(tree);
let entry_iterator = tree.entries_non_recursive(); let entry_iterator = tree.entries_non_recursive();
let entry_iterator: TreeEntriesNonRecursiveIterator<'static> = let entry_iterator: TreeEntriesNonRecursiveIterator<'static> =
unsafe { std::mem::transmute(entry_iterator) }; unsafe { std::mem::transmute(entry_iterator) };
@ -410,8 +409,8 @@ struct TreeDiffDirItem {
// Iterator over the diffs between tree1 and tree2 // Iterator over the diffs between tree1 and tree2
entry_iterator: TreeEntryDiffIterator<'static>, entry_iterator: TreeEntryDiffIterator<'static>,
// On drop, tree1 and tree2 must outlive entry_iterator // On drop, tree1 and tree2 must outlive entry_iterator
tree1: Pin<Box<Tree>>, tree1: Box<Tree>,
tree2: Pin<Box<Tree>>, tree2: Box<Tree>,
} }
enum TreeDiffItem { enum TreeDiffItem {
@ -434,8 +433,8 @@ impl<'matcher> TreeDiffIterator<'matcher> {
impl TreeDiffDirItem { impl TreeDiffDirItem {
fn new(path: RepoPath, tree1: Tree, tree2: Tree) -> Self { fn new(path: RepoPath, tree1: Tree, tree2: Tree) -> Self {
let tree1 = Box::pin(tree1); let tree1 = Box::new(tree1);
let tree2 = Box::pin(tree2); let tree2 = Box::new(tree2);
let iter: TreeEntryDiffIterator = diff_entries(&tree1, &tree2); let iter: TreeEntryDiffIterator = diff_entries(&tree1, &tree2);
let iter: TreeEntryDiffIterator<'static> = unsafe { std::mem::transmute(iter) }; let iter: TreeEntryDiffIterator<'static> = unsafe { std::mem::transmute(iter) };
Self { Self {