From f808430497525663dd3f62c294a3ae1762abdc22 Mon Sep 17 00:00:00 2001
From: Cameron Steffen <cam.steffen94@gmail.com>
Date: Wed, 26 Oct 2022 16:18:39 -0500
Subject: [PATCH] Factor out ITEM_REFS

---
 compiler/rustc_hir/src/lang_items.rs    | 26 +++++++++++++------------
 compiler/rustc_passes/src/lang_items.rs | 15 +++++++-------
 2 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 0735f58a922..9d1d84e32bb 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -12,14 +12,11 @@
 use crate::{MethodKind, Target};
 
 use rustc_ast as ast;
-use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_macros::HashStable_Generic;
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
 
-use std::sync::LazyLock;
-
 pub enum LangItemGroup {
     Op,
     Fn,
@@ -104,6 +101,14 @@ pub fn name(self) -> Symbol {
                 }
             }
 
+            /// Opposite of [`LangItem::name`]
+            pub fn from_name(name: Symbol) -> Option<Self> {
+                match name {
+                    $( $module::$name => Some(LangItem::$variant), )*
+                    _ => None,
+                }
+            }
+
             /// The [group](LangItemGroup) that this lang item belongs to,
             /// or `None` if it doesn't belong to a group.
             pub fn group(self) -> Option<LangItemGroup> {
@@ -113,6 +118,12 @@ pub fn group(self) -> Option<LangItemGroup> {
                 }
             }
 
+            pub fn target(self) -> Target {
+                match self {
+                    $( LangItem::$variant => $target, )*
+                }
+            }
+
             pub fn required_generics(&self) -> GenericRequirement {
                 match self {
                     $( LangItem::$variant => $generics, )*
@@ -145,15 +156,6 @@ pub fn $method(&self) -> Option<DefId> {
                 }
             )*
         }
-
-        /// A mapping from the name of the lang item to its order and the form it must be of.
-        pub static ITEM_REFS: LazyLock<FxIndexMap<Symbol, (usize, Target)>> = LazyLock::new(|| {
-            let mut item_refs = FxIndexMap::default();
-            $( item_refs.insert($module::$name, (LangItem::$variant as usize, $target)); )*
-            item_refs
-        });
-
-// End of the macro
     }
 }
 
diff --git a/compiler/rustc_passes/src/lang_items.rs b/compiler/rustc_passes/src/lang_items.rs
index cbd62ef4325..54be30d9fe5 100644
--- a/compiler/rustc_passes/src/lang_items.rs
+++ b/compiler/rustc_passes/src/lang_items.rs
@@ -16,7 +16,7 @@
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
-use rustc_hir::lang_items::{extract, GenericRequirement, ITEM_REFS};
+use rustc_hir::lang_items::{extract, GenericRequirement};
 use rustc_hir::{HirId, LangItem, LanguageItems, Target};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::cstore::ExternCrate;
@@ -43,17 +43,17 @@ fn new(tcx: TyCtxt<'tcx>) -> LanguageItemCollector<'tcx> {
     fn check_for_lang(&mut self, actual_target: Target, hir_id: HirId) {
         let attrs = self.tcx.hir().attrs(hir_id);
         if let Some((name, span)) = extract(&attrs) {
-            match ITEM_REFS.get(&name).cloned() {
+            match LangItem::from_name(name) {
                 // Known lang item with attribute on correct target.
-                Some((item_index, expected_target)) if actual_target == expected_target => {
-                    self.collect_item_extended(item_index, hir_id, span);
+                Some(lang_item) if actual_target == lang_item.target() => {
+                    self.collect_item_extended(lang_item, hir_id, span);
                 }
                 // Known lang item with attribute on incorrect target.
-                Some((_, expected_target)) => {
+                Some(lang_item) => {
                     self.tcx.sess.emit_err(LangItemOnIncorrectTarget {
                         span,
                         name,
-                        expected_target,
+                        expected_target: lang_item.target(),
                         actual_target,
                     });
                 }
@@ -147,9 +147,8 @@ fn collect_item(&mut self, lang_item: LangItem, item_def_id: DefId) {
 
     // Like collect_item() above, but also checks whether the lang item is declared
     // with the right number of generic arguments.
-    fn collect_item_extended(&mut self, item_index: usize, hir_id: HirId, span: Span) {
+    fn collect_item_extended(&mut self, lang_item: LangItem, hir_id: HirId, span: Span) {
         let item_def_id = self.tcx.hir().local_def_id(hir_id).to_def_id();
-        let lang_item = LangItem::from_u32(item_index as u32).unwrap();
         let name = lang_item.name();
 
         // Now check whether the lang_item has the expected number of generic