bjoernager/rust
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Auto merge of #105175 - michaelwoerister:add-stable-ord-trait, r=nagisa

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Add StableOrd trait as proposed in MCP 533.

The `StableOrd` trait can be used to mark types as having a stable sort order across compilation sessions. Collections that sort their items in a stable way can safely implement HashStable by hashing items in sort order.

See https://github.com/rust-lang/compiler-team/issues/533 for more information.
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bors 2022-12-06 09:21:49 +00:00
commit 9db224fc90
7 changed files with 95 additions and 35 deletions
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6
compiler/rustc_hir/src/hir_id.rs
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@ -1,5 +1,5 @@
use crate::def_id::{DefId, DefIndex, LocalDefId, CRATE_DEF_ID};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableOrd, ToStableHashKey};
use rustc_span::{def_id::DefPathHash, HashStableContext};
use std::fmt;
@ -146,6 +146,10 @@ impl ItemLocalId {
pub const INVALID: ItemLocalId = ItemLocalId::MAX;
}
// Safety: Ord is implement as just comparing the LocalItemId's numerical
// values and these are not changed by (de-)serialization.
unsafe impl StableOrd for ItemLocalId {}
/// The `HirId` corresponding to `CRATE_NODE_ID` and `CRATE_DEF_ID`.
pub const CRATE_HIR_ID: HirId =
HirId { owner: OwnerId { def_id: CRATE_DEF_ID }, local_id: ItemLocalId::from_u32(0) };