From c3ceb286fa92a713f8d3d4169c3acd4ffbffa820 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Thu, 30 Apr 2026 22:10:25 +1000
Subject: [PATCH 1/2] Remove unused `Feed` type.

---
 compiler/rustc_middle/src/ty/context.rs | 43 ++-----------------------
 compiler/rustc_middle/src/ty/mod.rs     |  2 +-
 2 files changed, 3 insertions(+), 42 deletions(-)

diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 2e9708483a85..ab7cd218bbeb 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -10,7 +10,7 @@
 use std::env::VarError;
 use std::ffi::OsStr;
 use std::hash::{Hash, Hasher};
-use std::marker::{PhantomData, PointeeSized};
+use std::marker::PointeeSized;
 use std::ops::{Bound, Deref};
 use std::sync::{Arc, OnceLock};
 use std::{fmt, iter, mem};
@@ -545,31 +545,9 @@ pub struct TyCtxtFeed<'tcx, KEY: Copy> {
     key: KEY,
 }
 
-/// Never return a `Feed` from a query. Only queries that create a `DefId` are
-/// allowed to feed queries for that `DefId`.
+/// Only queries that create a `DefId` are allowed to feed queries for that `DefId`.
 impl<KEY: Copy> !HashStable for TyCtxtFeed<'_, KEY> {}
 
-/// The same as `TyCtxtFeed`, but does not contain a `TyCtxt`.
-/// Use this to pass around when you have a `TyCtxt` elsewhere.
-/// Just an optimization to save space and not store hundreds of
-/// `TyCtxtFeed` in the resolver.
-#[derive(Copy, Clone)]
-pub struct Feed<'tcx, KEY: Copy> {
-    _tcx: PhantomData<TyCtxt<'tcx>>,
-    // Do not allow direct access, as downstream code must not mutate this field.
-    key: KEY,
-}
-
-/// Never return a `Feed` from a query. Only queries that create a `DefId` are
-/// allowed to feed queries for that `DefId`.
-impl<KEY: Copy> !HashStable for Feed<'_, KEY> {}
-
-impl<T: fmt::Debug + Copy> fmt::Debug for Feed<'_, T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.key.fmt(f)
-    }
-}
-
 /// Some workarounds to use cases that cannot use `create_def`.
 /// Do not add new ways to create `TyCtxtFeed` without consulting
 /// with T-compiler and making an analysis about why your addition
@@ -627,23 +605,6 @@ impl<'tcx, KEY: Copy> TyCtxtFeed<'tcx, KEY> {
     pub fn key(&self) -> KEY {
         self.key
     }
-
-    #[inline(always)]
-    pub fn downgrade(self) -> Feed<'tcx, KEY> {
-        Feed { _tcx: PhantomData, key: self.key }
-    }
-}
-
-impl<'tcx, KEY: Copy> Feed<'tcx, KEY> {
-    #[inline(always)]
-    pub fn key(&self) -> KEY {
-        self.key
-    }
-
-    #[inline(always)]
-    pub fn upgrade(self, tcx: TyCtxt<'tcx>) -> TyCtxtFeed<'tcx, KEY> {
-        TyCtxtFeed { tcx, key: self.key }
-    }
 }
 
 impl<'tcx> TyCtxtFeed<'tcx, LocalDefId> {
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 914fb4314715..74cad5acfc6f 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -83,7 +83,7 @@
     const_lit_matches_ty,
 };
 pub use self::context::{
-    CtxtInterners, CurrentGcx, Feed, FreeRegionInfo, GlobalCtxt, Lift, TyCtxt, TyCtxtFeed, tls,
+    CtxtInterners, CurrentGcx, FreeRegionInfo, GlobalCtxt, Lift, TyCtxt, TyCtxtFeed, tls,
 };
 pub use self::fold::*;
 pub use self::instance::{Instance, InstanceKind, ReifyReason};

From ddc626d2e10217286e55081fcedf254543638fb9 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Thu, 30 Apr 2026 22:13:13 +1000
Subject: [PATCH 2/2] Rename `KEY` type parameters as `K`.

RFC 430 says type parameters should be named "concise UpperCamelCase,
usually single uppercase letter". So either `Key` or `K` is more
appropriate than `KEY`, which looks like a constant.

I chose `K` because it's a well-known abbreviation of "key" used in lots
of places, e.g. `HashMap<K, V>`.
---
 compiler/rustc_middle/src/ty/context.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index ab7cd218bbeb..26f0760b3c56 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -539,14 +539,14 @@ pub struct FreeRegionInfo {
 
 /// This struct should only be created by `create_def`.
 #[derive(Copy, Clone)]
-pub struct TyCtxtFeed<'tcx, KEY: Copy> {
+pub struct TyCtxtFeed<'tcx, K: Copy> {
     pub tcx: TyCtxt<'tcx>,
     // Do not allow direct access, as downstream code must not mutate this field.
-    key: KEY,
+    key: K,
 }
 
 /// Only queries that create a `DefId` are allowed to feed queries for that `DefId`.
-impl<KEY: Copy> !HashStable for TyCtxtFeed<'_, KEY> {}
+impl<K: Copy> !HashStable for TyCtxtFeed<'_, K> {}
 
 /// Some workarounds to use cases that cannot use `create_def`.
 /// Do not add new ways to create `TyCtxtFeed` without consulting
@@ -600,9 +600,9 @@ pub fn feed_visibility_for_trait_impl_item(self, key: LocalDefId, vis: ty::Visib
     }
 }
 
-impl<'tcx, KEY: Copy> TyCtxtFeed<'tcx, KEY> {
+impl<'tcx, K: Copy> TyCtxtFeed<'tcx, K> {
     #[inline(always)]
-    pub fn key(&self) -> KEY {
+    pub fn key(&self) -> K {
         self.key
     }
 }