From 4375af53af48febdd3534d8d300b7769a4e0fb1c Mon Sep 17 00:00:00 2001
From: Maybe Waffle <waffle.lapkin@gmail.com>
Date: Thu, 20 Apr 2023 18:46:29 +0000
Subject: [PATCH] Derive `HashStable` on `GenericArgKind` instead of
implementing it by hand
---
compiler/rustc_middle/src/ty/impls_ty.rs | 28 ------------------------
compiler/rustc_middle/src/ty/subst.rs | 2 +-
2 files changed, 1 insertion(+), 29 deletions(-)
diff --git a/compiler/rustc_middle/src/ty/impls_ty.rs b/compiler/rustc_middle/src/ty/impls_ty.rs
index 4c7822acdf785..02baa395c3c2f 100644
--- a/compiler/rustc_middle/src/ty/impls_ty.rs
+++ b/compiler/rustc_middle/src/ty/impls_ty.rs
@@ -73,34 +73,6 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArg<'t
}
}
-impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArgKind<'tcx> {
- fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
- match self {
- // WARNING: We dedup cache the `HashStable` results for `List`
- // while ignoring types and freely transmute
- // between `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>`.
- // See `fn mk_type_list` for more details.
- //
- // We therefore hash types without adding a hash for their discriminant.
- //
- // In order to make it very unlikely for the sequence of bytes being hashed for
- // a `GenericArgKind::Type` to be the same as the sequence of bytes being
- // hashed for one of the other variants, we hash some very high number instead
- // of their actual discriminant since `TyKind` should never start with anything
- // that high.
- ty::subst::GenericArgKind::Type(ty) => ty.hash_stable(hcx, hasher),
- ty::subst::GenericArgKind::Const(ct) => {
- 0xF3u8.hash_stable(hcx, hasher);
- ct.hash_stable(hcx, hasher);
- }
- ty::subst::GenericArgKind::Lifetime(lt) => {
- 0xF5u8.hash_stable(hcx, hasher);
- lt.hash_stable(hcx, hasher);
- }
- }
- }
-}
-
// AllocIds get resolved to whatever they point to (to be stable)
impl<'a> HashStable<StableHashingContext<'a>> for mir::interpret::AllocId {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/subst.rs
index 3e1b0706f6688..2b85eb971ce83 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/subst.rs
@@ -48,7 +48,7 @@ const TYPE_TAG: usize = 0b00;
const REGION_TAG: usize = 0b01;
const CONST_TAG: usize = 0b10;
-#[derive(Debug, TyEncodable, TyDecodable, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Debug, TyEncodable, TyDecodable, PartialEq, Eq, PartialOrd, Ord, HashStable)]
pub enum GenericArgKind<'tcx> {
Lifetime(ty::Region<'tcx>),
Type(Ty<'tcx>),