From d3812ac95fbf67725f1d13392a611b776b1a2608 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Wed, 12 Jun 2024 18:15:33 -0400
Subject: [PATCH] LangItem-ify Coroutine trait in solvers

---
 compiler/rustc_hir/src/lang_items.rs                |  4 +++-
 compiler/rustc_span/src/symbol.rs                   |  2 ++
 .../src/solve/normalizes_to/mod.rs                  | 13 ++++++++-----
 .../rustc_trait_selection/src/traits/project.rs     |  9 +++++----
 library/core/src/ops/coroutine.rs                   |  2 ++
 5 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index c3ccba487ed..69461957f80 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -244,7 +244,9 @@ language_item_table! {
     AsyncIterator,           sym::async_iterator,      async_iterator_trait,       Target::Trait,          GenericRequirement::Exact(0);
 
     CoroutineState,          sym::coroutine_state,     coroutine_state,            Target::Enum,           GenericRequirement::None;
-    Coroutine,               sym::coroutine,           coroutine_trait,            Target::Trait,          GenericRequirement::Minimum(1);
+    Coroutine,               sym::coroutine,           coroutine_trait,            Target::Trait,          GenericRequirement::Exact(1);
+    CoroutineReturn,         sym::coroutine_return,    coroutine_return,           Target::AssocTy,        GenericRequirement::Exact(1);
+    CoroutineYield,          sym::coroutine_yield,     coroutine_yield,            Target::AssocTy,        GenericRequirement::Exact(1);
     CoroutineResume,         sym::coroutine_resume,    coroutine_resume,           Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
 
     Unpin,                   sym::unpin,               unpin_trait,                Target::Trait,          GenericRequirement::None;
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index e245dfb9f5d..c89323b7f16 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -635,7 +635,9 @@ symbols! {
         coroutine,
         coroutine_clone,
         coroutine_resume,
+        coroutine_return,
         coroutine_state,
+        coroutine_yield,
         coroutines,
         cosf128,
         cosf16,
diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
index 787f08a084e..50253d81528 100644
--- a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
@@ -17,7 +17,7 @@ use rustc_middle::ty::NormalizesTo;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{TypeVisitableExt, Upcast};
 use rustc_middle::{bug, span_bug};
-use rustc_span::{sym, ErrorGuaranteed, DUMMY_SP};
+use rustc_span::{ErrorGuaranteed, DUMMY_SP};
 
 mod anon_const;
 mod inherent;
@@ -719,13 +719,16 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
 
         let coroutine = args.as_coroutine();
 
-        let name = tcx.associated_item(goal.predicate.def_id()).name;
-        let term = if name == sym::Return {
+        let lang_items = tcx.lang_items();
+        let term = if Some(goal.predicate.def_id()) == lang_items.coroutine_return() {
             coroutine.return_ty().into()
-        } else if name == sym::Yield {
+        } else if Some(goal.predicate.def_id()) == lang_items.coroutine_yield() {
             coroutine.yield_ty().into()
         } else {
-            bug!("unexpected associated item `<{self_ty} as Coroutine>::{name}`")
+            bug!(
+                "unexpected associated item `<{self_ty} as Coroutine>::{}`",
+                tcx.item_name(goal.predicate.def_id())
+            )
         };
 
         Self::probe_and_consider_implied_clause(
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 2c9cb79664b..32409e13842 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1373,15 +1373,16 @@ fn confirm_coroutine_candidate<'cx, 'tcx>(
         coroutine_sig,
     );
 
-    let name = tcx.associated_item(obligation.predicate.def_id).name;
-    let ty = if name == sym::Return {
+    let lang_items = tcx.lang_items();
+    let ty = if Some(obligation.predicate.def_id) == lang_items.coroutine_return() {
         return_ty
-    } else if name == sym::Yield {
+    } else if Some(obligation.predicate.def_id) == lang_items.coroutine_yield() {
         yield_ty
     } else {
         span_bug!(
             tcx.def_span(obligation.predicate.def_id),
-            "unexpected associated type: `Coroutine::{name}`"
+            "unexpected associated type: `Coroutine::{}`",
+            tcx.item_name(obligation.predicate.def_id),
         );
     };
 
diff --git a/library/core/src/ops/coroutine.rs b/library/core/src/ops/coroutine.rs
index 6a6c5db1ab1..753f14c6b85 100644
--- a/library/core/src/ops/coroutine.rs
+++ b/library/core/src/ops/coroutine.rs
@@ -76,6 +76,7 @@ pub trait Coroutine<R = ()> {
     /// values which are allowed to be returned each time a coroutine yields.
     /// For example an iterator-as-a-coroutine would likely have this type as
     /// `T`, the type being iterated over.
+    #[cfg_attr(not(bootstrap), lang = "coroutine_yield")]
     type Yield;
 
     /// The type of value this coroutine returns.
@@ -84,6 +85,7 @@ pub trait Coroutine<R = ()> {
     /// `return` statement or implicitly as the last expression of a coroutine
     /// literal. For example futures would use this as `Result<T, E>` as it
     /// represents a completed future.
+    #[cfg_attr(not(bootstrap), lang = "coroutine_return")]
     type Return;
 
     /// Resumes the execution of this coroutine.