Collect lang items from AST, get rid of GenericBound::LangItemTrait

compiler/rustc_ast/src/ast.rs

@@ -2845,6 +2845,28 @@ impl Item {
     pub fn span_with_attributes(&self) -> Span {
         self.attrs.iter().fold(self.span, |acc, attr| acc.to(attr.span))
     }
+
+    pub fn opt_generics(&self) -> Option<&Generics> {
+        match &self.kind {
+            ItemKind::ExternCrate(_)
+            | ItemKind::Use(_)
+            | ItemKind::Mod(_, _)
+            | ItemKind::ForeignMod(_)
+            | ItemKind::GlobalAsm(_)
+            | ItemKind::MacCall(_)
+            | ItemKind::MacroDef(_) => None,
+            ItemKind::Static(_) => None,
+            ItemKind::Const(i) => Some(&i.generics),
+            ItemKind::Fn(i) => Some(&i.generics),
+            ItemKind::TyAlias(i) => Some(&i.generics),
+            ItemKind::TraitAlias(generics, _)
+            | ItemKind::Enum(_, generics)
+            | ItemKind::Struct(_, generics)
+            | ItemKind::Union(_, generics) => Some(&generics),
+            ItemKind::Trait(i) => Some(&i.generics),
+            ItemKind::Impl(i) => Some(&i.generics),
+        }
+    }
 }
 
 /// `extern` qualifier on a function item or function type.

compiler/rustc_ast_lowering/src/lib.rs

@@ -453,6 +453,7 @@ pub fn lower_to_hir(tcx: TyCtxt<'_>, (): ()) -> hir::Crate<'_> {
     tcx.ensure_with_value().output_filenames(());
     tcx.ensure_with_value().early_lint_checks(());
     tcx.ensure_with_value().debugger_visualizers(LOCAL_CRATE);
+    tcx.ensure_with_value().get_lang_items(());
     let (mut resolver, krate) = tcx.resolver_for_lowering(()).steal();
 
     let ast_index = index_crate(&resolver.node_id_to_def_id, &krate);
@@ -765,6 +766,28 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.resolver.get_import_res(id).present_items()
     }
 
+    fn make_lang_item_path(
+        &mut self,
+        lang_item: hir::LangItem,
+        span: Span,
+        args: Option<&'hir hir::GenericArgs<'hir>>,
+    ) -> &'hir hir::Path<'hir> {
+        let def_id = self.tcx.require_lang_item(lang_item, Some(span));
+        let def_kind = self.tcx.def_kind(def_id);
+        let res = Res::Def(def_kind, def_id);
+        self.arena.alloc(hir::Path {
+            span,
+            res,
+            segments: self.arena.alloc_from_iter([hir::PathSegment {
+                ident: Ident::new(lang_item.name(), span),
+                hir_id: self.next_id(),
+                res,
+                args,
+                infer_args: false,
+            }]),
+        })
+    }
+
     /// Reuses the span but adds information like the kind of the desugaring and features that are
     /// allowed inside this span.
     fn mark_span_with_reason(
@@ -1976,18 +1999,27 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             CoroutineKind::AsyncGen { .. } => (sym::Item, hir::LangItem::AsyncIterator),
         };
 
-        let future_args = self.arena.alloc(hir::GenericArgs {
+        let bound_args = self.arena.alloc(hir::GenericArgs {
             args: &[],
             bindings: arena_vec![self; self.assoc_ty_binding(assoc_ty_name, opaque_ty_span, output_ty)],
             parenthesized: hir::GenericArgsParentheses::No,
             span_ext: DUMMY_SP,
         });
 
-        hir::GenericBound::LangItemTrait(
-            trait_lang_item,
-            opaque_ty_span,
-            self.next_id(),
-            future_args,
+        hir::GenericBound::Trait(
+            hir::PolyTraitRef {
+                bound_generic_params: &[],
+                trait_ref: hir::TraitRef {
+                    path: self.make_lang_item_path(
+                        trait_lang_item,
+                        opaque_ty_span,
+                        Some(bound_args),
+                    ),
+                    hir_ref_id: self.next_id(),
+                },
+                span: opaque_ty_span,
+            },
+            hir::TraitBoundModifier::None,
         )
     }
 

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -788,28 +788,18 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         };
         let opaque_ty = hir.item(id);
         if let hir::ItemKind::OpaqueTy(hir::OpaqueTy {
-            bounds:
-                [
-                    hir::GenericBound::LangItemTrait(
-                        hir::LangItem::Future,
-                        _,
-                        _,
-                        hir::GenericArgs {
-                            bindings:
-                                [
-                                    hir::TypeBinding {
-                                        ident: Ident { name: sym::Output, .. },
-                                        kind:
-                                            hir::TypeBindingKind::Equality { term: hir::Term::Ty(ty) },
-                                        ..
-                                    },
-                                ],
-                            ..
-                        },
-                    ),
-                ],
+            bounds: [hir::GenericBound::Trait(trait_ref, _)],
             ..
         }) = opaque_ty.kind
+            && let Some(segment) = trait_ref.trait_ref.path.segments.last()
+            && let Some(args) = segment.args
+            && let [
+                hir::TypeBinding {
+                    ident: Ident { name: sym::Output, .. },
+                    kind: hir::TypeBindingKind::Equality { term: hir::Term::Ty(ty) },
+                    ..
+                },
+            ] = args.bindings
         {
             ty
         } else {

compiler/rustc_hir/src/hir.rs

@@ -435,8 +435,6 @@ pub enum TraitBoundModifier {
 #[derive(Clone, Copy, Debug, HashStable_Generic)]
 pub enum GenericBound<'hir> {
     Trait(PolyTraitRef<'hir>, TraitBoundModifier),
-    // FIXME(davidtwco): Introduce `PolyTraitRef::LangItem`
-    LangItemTrait(LangItem, Span, HirId, &'hir GenericArgs<'hir>),
     Outlives(&'hir Lifetime),
 }
 
@@ -451,7 +449,6 @@ impl GenericBound<'_> {
     pub fn span(&self) -> Span {
         match self {
             GenericBound::Trait(t, ..) => t.span,
-            GenericBound::LangItemTrait(_, span, ..) => *span,
             GenericBound::Outlives(l) => l.ident.span,
         }
     }

compiler/rustc_hir/src/intravisit.rs

@@ -1075,10 +1075,6 @@ pub fn walk_param_bound<'v, V: Visitor<'v>>(visitor: &mut V, bound: &'v GenericB
         GenericBound::Trait(ref typ, _modifier) => {
             visitor.visit_poly_trait_ref(typ);
         }
-        GenericBound::LangItemTrait(_, _span, hir_id, args) => {
-            visitor.visit_id(hir_id);
-            visitor.visit_generic_args(args);
-        }
         GenericBound::Outlives(ref lifetime) => visitor.visit_lifetime(lifetime),
     }
 }

compiler/rustc_hir/src/target.rs

@@ -67,6 +67,42 @@ impl Display for Target {
 }
 
 impl Target {
+    pub fn is_associated_item(self) -> bool {
+        match self {
+            Target::AssocConst | Target::AssocTy | Target::Method(_) => true,
+            Target::ExternCrate
+            | Target::Use
+            | Target::Static
+            | Target::Const
+            | Target::Fn
+            | Target::Closure
+            | Target::Mod
+            | Target::ForeignMod
+            | Target::GlobalAsm
+            | Target::TyAlias
+            | Target::OpaqueTy
+            | Target::Enum
+            | Target::Variant
+            | Target::Struct
+            | Target::Field
+            | Target::Union
+            | Target::Trait
+            | Target::TraitAlias
+            | Target::Impl
+            | Target::Expression
+            | Target::Statement
+            | Target::Arm
+            | Target::ForeignFn
+            | Target::ForeignStatic
+            | Target::ForeignTy
+            | Target::GenericParam(_)
+            | Target::MacroDef
+            | Target::Param
+            | Target::PatField
+            | Target::ExprField => false,
+        }
+    }
+
     pub fn from_item(item: &Item<'_>) -> Target {
         match item.kind {
             ItemKind::ExternCrate(..) => Target::ExternCrate,

compiler/rustc_hir_analysis/src/astconv/bounds.rs

@@ -134,17 +134,6 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
                         only_self_bounds,
                     );
                 }
-                &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => {
-                    self.instantiate_lang_item_trait_ref(
-                        lang_item,
-                        span,
-                        hir_id,
-                        args,
-                        param_ty,
-                        bounds,
-                        only_self_bounds,
-                    );
-                }
                 hir::GenericBound::Outlives(lifetime) => {
                     let region = self.ast_region_to_region(lifetime, None);
                     bounds.push_region_bound(

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -675,36 +675,57 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         )
     }
 
-    fn instantiate_poly_trait_ref_inner(
+    /// Given a trait bound like `Debug`, applies that trait bound the given self-type to construct
+    /// a full trait reference. The resulting trait reference is returned. This may also generate
+    /// auxiliary bounds, which are added to `bounds`.
+    ///
+    /// Example:
+    ///
+    /// ```ignore (illustrative)
+    /// poly_trait_ref = Iterator<Item = u32>
+    /// self_ty = Foo
+    /// ```
+    ///
+    /// this would return `Foo: Iterator` and add `<Foo as Iterator>::Item = u32` into `bounds`.
+    ///
+    /// **A note on binders:** against our usual convention, there is an implied binder around
+    /// the `self_ty` and `poly_trait_ref` parameters here. So they may reference bound regions.
+    /// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>`
+    /// where `'a` is a bound region at depth 0. Similarly, the `poly_trait_ref` would be
+    /// `Bar<'a>`. The returned poly-trait-ref will have this binder instantiated explicitly,
+    /// however.
+    #[instrument(level = "debug", skip(self, span, constness, bounds, speculative))]
+    pub(crate) fn instantiate_poly_trait_ref(
         &self,
-        hir_id: hir::HirId,
+        trait_ref: &hir::TraitRef<'_>,
         span: Span,
-        binding_span: Option<Span>,
         constness: ty::BoundConstness,
         polarity: ty::ImplPolarity,
+        self_ty: Ty<'tcx>,
         bounds: &mut Bounds<'tcx>,
         speculative: bool,
-        trait_ref_span: Span,
-        trait_def_id: DefId,
-        trait_segment: &hir::PathSegment<'_>,
-        args: &GenericArgs<'_>,
-        infer_args: bool,
-        self_ty: Ty<'tcx>,
         only_self_bounds: OnlySelfBounds,
     ) -> GenericArgCountResult {
+        let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise());
+        let trait_segment = trait_ref.path.segments.last().unwrap();
+        let args = trait_segment.args();
+
+        self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1.iter(), |_| {});
+        self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, false);
+
         let (generic_args, arg_count) = self.create_args_for_ast_path(
-            trait_ref_span,
+            trait_ref.path.span,
             trait_def_id,
             &[],
             trait_segment,
             args,
-            infer_args,
+            trait_segment.infer_args,
             Some(self_ty),
             constness,
         );
 
         let tcx = self.tcx();
-        let bound_vars = tcx.late_bound_vars(hir_id);
+        let bound_vars = tcx.late_bound_vars(trait_ref.hir_ref_id);
         debug!(?bound_vars);
 
         let assoc_bindings = self.create_assoc_bindings_for_generic_args(args);
@@ -732,13 +753,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
             // Specify type to assert that error was already reported in `Err` case.
             let _: Result<_, ErrorGuaranteed> = self.add_predicates_for_ast_type_binding(
-                hir_id,
+                trait_ref.hir_ref_id,
                 poly_trait_ref,
                 binding,
                 bounds,
                 speculative,
                 &mut dup_bindings,
-                binding_span.unwrap_or(binding.span),
+                binding.span,
                 constness,
                 only_self_bounds,
                 polarity,
@@ -749,102 +770,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         arg_count
     }
 
-    /// Given a trait bound like `Debug`, applies that trait bound the given self-type to construct
-    /// a full trait reference. The resulting trait reference is returned. This may also generate
-    /// auxiliary bounds, which are added to `bounds`.
-    ///
-    /// Example:
-    ///
-    /// ```ignore (illustrative)
-    /// poly_trait_ref = Iterator<Item = u32>
-    /// self_ty = Foo
-    /// ```
-    ///
-    /// this would return `Foo: Iterator` and add `<Foo as Iterator>::Item = u32` into `bounds`.
-    ///
-    /// **A note on binders:** against our usual convention, there is an implied bounder around
-    /// the `self_ty` and `poly_trait_ref` parameters here. So they may reference bound regions.
-    /// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>`
-    /// where `'a` is a bound region at depth 0. Similarly, the `poly_trait_ref` would be
-    /// `Bar<'a>`. The returned poly-trait-ref will have this binder instantiated explicitly,
-    /// however.
-    #[instrument(level = "debug", skip(self, span, constness, bounds, speculative))]
-    pub(crate) fn instantiate_poly_trait_ref(
-        &self,
-        trait_ref: &hir::TraitRef<'_>,
-        span: Span,
-        constness: ty::BoundConstness,
-        polarity: ty::ImplPolarity,
-        self_ty: Ty<'tcx>,
-        bounds: &mut Bounds<'tcx>,
-        speculative: bool,
-        only_self_bounds: OnlySelfBounds,
-    ) -> GenericArgCountResult {
-        let hir_id = trait_ref.hir_ref_id;
-        let binding_span = None;
-        let trait_ref_span = trait_ref.path.span;
-        let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise());
-        let trait_segment = trait_ref.path.segments.last().unwrap();
-        let args = trait_segment.args();
-        let infer_args = trait_segment.infer_args;
-
-        self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1.iter(), |_| {});
-        self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, false);
-
-        self.instantiate_poly_trait_ref_inner(
-            hir_id,
-            span,
-            binding_span,
-            constness,
-            polarity,
-            bounds,
-            speculative,
-            trait_ref_span,
-            trait_def_id,
-            trait_segment,
-            args,
-            infer_args,
-            self_ty,
-            only_self_bounds,
-        )
-    }
-
-    pub(crate) fn instantiate_lang_item_trait_ref(
-        &self,
-        lang_item: hir::LangItem,
-        span: Span,
-        hir_id: hir::HirId,
-        args: &GenericArgs<'_>,
-        self_ty: Ty<'tcx>,
-        bounds: &mut Bounds<'tcx>,
-        only_self_bounds: OnlySelfBounds,
-    ) {
-        let binding_span = Some(span);
-        let constness = ty::BoundConstness::NotConst;
-        let speculative = false;
-        let trait_ref_span = span;
-        let trait_def_id = self.tcx().require_lang_item(lang_item, Some(span));
-        let trait_segment = &hir::PathSegment::invalid();
-        let infer_args = false;
-
-        self.instantiate_poly_trait_ref_inner(
-            hir_id,
-            span,
-            binding_span,
-            constness,
-            ty::ImplPolarity::Positive,
-            bounds,
-            speculative,
-            trait_ref_span,
-            trait_def_id,
-            trait_segment,
-            args,
-            infer_args,
-            self_ty,
-            only_self_bounds,
-        );
-    }
-
     fn ast_path_to_mono_trait_ref(
         &self,
         span: Span,

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -938,32 +938,6 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
         }
     }
 
-    fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) {
-        match bound {
-            hir::GenericBound::LangItemTrait(_, _, hir_id, _) => {
-                // FIXME(jackh726): This is pretty weird. `LangItemTrait` doesn't go
-                // through the regular poly trait ref code, so we don't get another
-                // chance to introduce a binder. For now, I'm keeping the existing logic
-                // of "if there isn't a Binder scope above us, add one", but I
-                // imagine there's a better way to go about this.
-                let (binders, scope_type) = self.poly_trait_ref_binder_info();
-
-                self.record_late_bound_vars(*hir_id, binders);
-                let scope = Scope::Binder {
-                    hir_id: *hir_id,
-                    bound_vars: FxIndexMap::default(),
-                    s: self.scope,
-                    scope_type,
-                    where_bound_origin: None,
-                };
-                self.with(scope, |this| {
-                    intravisit::walk_param_bound(this, bound);
-                });
-            }
-            _ => intravisit::walk_param_bound(self, bound),
-        }
-    }
-
     fn visit_poly_trait_ref(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) {
         self.visit_poly_trait_ref_inner(trait_ref, NonLifetimeBinderAllowed::Allow);
     }

compiler/rustc_hir_pretty/src/lib.rs

@@ -2088,11 +2088,6 @@ impl<'a> State<'a> {
                     }
                     self.print_poly_trait_ref(tref);
                 }
-                GenericBound::LangItemTrait(lang_item, span, ..) => {
-                    self.word("#[lang = \"");
-                    self.print_ident(Ident::new(lang_item.name(), *span));
-                    self.word("\"]");
-                }
                 GenericBound::Outlives(lt) => {
                     self.print_lifetime(lt);
                 }

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -825,9 +825,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && let hir::Node::Item(hir::Item {
                         kind: hir::ItemKind::OpaqueTy(op_ty), ..
                     }) = self.tcx.hir_node(item_id.hir_id())
-                    && let [
-                        hir::GenericBound::LangItemTrait(hir::LangItem::Future, _, _, generic_args),
-                    ] = op_ty.bounds
+                    && let [hir::GenericBound::Trait(trait_ref, _)] = op_ty.bounds
+                    && let Some(hir::PathSegment { args: Some(generic_args), .. }) =
+                        trait_ref.trait_ref.path.segments.last()
                     && let hir::GenericArgs { bindings: [ty_binding], .. } = generic_args
                     && let hir::TypeBindingKind::Equality { term: hir::Term::Ty(term) } =
                         ty_binding.kind

compiler/rustc_infer/src/infer/error_reporting/suggest.rs

@@ -668,26 +668,16 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     (
                         hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: last_bounds, .. }),
                         hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: exp_bounds, .. }),
-                    ) if std::iter::zip(*last_bounds, *exp_bounds).all(|(left, right)| {
-                        match (left, right) {
-                            (
-                                hir::GenericBound::Trait(tl, ml),
-                                hir::GenericBound::Trait(tr, mr),
-                            ) if tl.trait_ref.trait_def_id() == tr.trait_ref.trait_def_id()
+                    ) if std::iter::zip(*last_bounds, *exp_bounds).all(|(left, right)| match (
+                        left, right,
+                    ) {
+                        (hir::GenericBound::Trait(tl, ml), hir::GenericBound::Trait(tr, mr))
+                            if tl.trait_ref.trait_def_id() == tr.trait_ref.trait_def_id()
                                 && ml == mr =>
-                            {
-                                true
-                            }
-                            (
-                                hir::GenericBound::LangItemTrait(langl, _, _, argsl),
-                                hir::GenericBound::LangItemTrait(langr, _, _, argsr),
-                            ) if langl == langr => {
-                                // FIXME: consider the bounds!
-                                debug!("{:?} {:?}", argsl, argsr);
-                                true
-                            }
-                            _ => false,
+                        {
+                            true
                         }
+                        _ => false,
                     }) =>
                     {
                         StatementAsExpression::NeedsBoxing

compiler/rustc_passes/src/hir_stats.rs

@@ -429,7 +429,7 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
     fn visit_param_bound(&mut self, b: &'v hir::GenericBound<'v>) {
         record_variants!(
             (self, b, b, Id::None, hir, GenericBound, GenericBound),
-            [Trait, LangItemTrait, Outlives]
+            [Trait, Outlives]
         );
         hir_visit::walk_param_bound(self, b)
     }

compiler/rustc_passes/src/weak_lang_items.rs

@@ -1,5 +1,7 @@
 //! Validity checking for weak lang items
 
+use rustc_ast as ast;
+use rustc_ast::visit;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::lang_items::{self, LangItem};
 use rustc_hir::weak_lang_items::WEAK_LANG_ITEMS;
@@ -11,7 +13,7 @@ use crate::errors::{MissingLangItem, MissingPanicHandler, UnknownExternLangItem}
 
 /// Checks the crate for usage of weak lang items, returning a vector of all the
 /// language items required by this crate, but not defined yet.
-pub fn check_crate(tcx: TyCtxt<'_>, items: &mut lang_items::LanguageItems) {
+pub fn check_crate(tcx: TyCtxt<'_>, items: &mut lang_items::LanguageItems, krate: &ast::Crate) {
     // These are never called by user code, they're generated by the compiler.
     // They will never implicitly be added to the `missing` array unless we do
     // so here.
@@ -22,24 +24,30 @@ pub fn check_crate(tcx: TyCtxt<'_>, items: &mut lang_items::LanguageItems) {
         items.missing.push(LangItem::EhCatchTypeinfo);
     }
 
-    let crate_items = tcx.hir_crate_items(());
-    for id in crate_items.foreign_items() {
-        let attrs = tcx.hir().attrs(id.hir_id());
-        if let Some((lang_item, _)) = lang_items::extract(attrs) {
+    visit::Visitor::visit_crate(&mut WeakLangItemVisitor { tcx, items }, krate);
+
+    verify(tcx, items);
+}
+
+struct WeakLangItemVisitor<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    items: &'a mut lang_items::LanguageItems,
+}
+
+impl<'ast> visit::Visitor<'ast> for WeakLangItemVisitor<'_, '_> {
+    fn visit_foreign_item(&mut self, i: &'ast ast::ForeignItem) {
+        if let Some((lang_item, _)) = lang_items::extract(&i.attrs) {
             if let Some(item) = LangItem::from_name(lang_item)
                 && item.is_weak()
             {
-                if items.get(item).is_none() {
-                    items.missing.push(item);
+                if self.items.get(item).is_none() {
+                    self.items.missing.push(item);
                 }
             } else {
-                let span = tcx.def_span(id.owner_id);
-                tcx.sess.emit_err(UnknownExternLangItem { span, lang_item });
+                self.tcx.sess.emit_err(UnknownExternLangItem { span: i.span, lang_item });
             }
         }
     }
-
-    verify(tcx, items);
 }
 
 fn verify(tcx: TyCtxt<'_>, items: &lang_items::LanguageItems) {

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -4783,8 +4783,14 @@ pub fn suggest_desugaring_async_fn_to_impl_future_in_trait<'tcx>(
     };
 
     let future = tcx.hir_node_by_def_id(opaque_def_id).expect_item().expect_opaque_ty();
-    let Some(hir::GenericBound::LangItemTrait(_, _, _, generics)) = future.bounds.get(0) else {
-        // `async fn` should always lower to a lang item bound... but don't ICE.
+    let [hir::GenericBound::Trait(trait_ref, _)] = future.bounds else {
+        // `async fn` should always lower to a single bound... but don't ICE.
+        return None;
+    };
+    let Some(hir::PathSegment { args: Some(generics), .. }) =
+        trait_ref.trait_ref.path.segments.last()
+    else {
+        // desugaring to a single path segment for `Future<...>`.
         return None;
     };
     let Some(hir::TypeBindingKind::Equality { term: hir::Term::Ty(future_output_ty) }) =

library/std/src/panicking.rs

@@ -588,7 +588,7 @@ pub fn panicking() -> bool {
 }
 
 /// Entry point of panics from the core crate (`panic_impl` lang item).
-#[cfg(not(test))]
+#[cfg(not(any(test, doctest)))]
 #[panic_handler]
 pub fn begin_panic_handler(info: &PanicInfo<'_>) -> ! {
     struct FormatStringPayload<'a> {
@@ -669,7 +669,7 @@ pub fn begin_panic_handler(info: &PanicInfo<'_>) -> ! {
 /// panic!() and assert!(). In particular, this is the only entry point that supports
 /// arbitrary payloads, not just format strings.
 #[unstable(feature = "libstd_sys_internals", reason = "used by the panic! macro", issue = "none")]
-#[cfg_attr(not(test), lang = "begin_panic")]
+#[cfg_attr(not(any(test, doctest)), lang = "begin_panic")]
 // lang item for CTFE panic support
 // never inline unless panic_immediate_abort to avoid code
 // bloat at the call sites as much as possible

library/std/src/process.rs

@@ -2311,7 +2311,7 @@ pub fn id() -> u32 {
 /// of the `main` function, this trait is likely to be available only on
 /// standard library's runtime for convenience. Other runtimes are not required
 /// to provide similar functionality.
-#[cfg_attr(not(test), lang = "termination")]
+#[cfg_attr(not(any(test, doctest)), lang = "termination")]
 #[stable(feature = "termination_trait_lib", since = "1.61.0")]
 #[rustc_on_unimplemented(on(
     cause = "MainFunctionType",

library/std/src/rt.rs

@@ -154,7 +154,7 @@ fn lang_start_internal(
     ret_code
 }
 
-#[cfg(not(test))]
+#[cfg(not(any(test, doctest)))]
 #[lang = "start"]
 fn lang_start<T: crate::process::Termination + 'static>(
     main: fn() -> T,

library/std/src/sys/personality/mod.rs

@@ -12,7 +12,7 @@
 
 mod dwarf;
 
-#[cfg(not(test))]
+#[cfg(not(any(test, doctest)))]
 cfg_if::cfg_if! {
     if #[cfg(target_os = "emscripten")] {
         mod emcc;

src/librustdoc/clean/mod.rs

@@ -184,22 +184,6 @@ fn clean_generic_bound<'tcx>(
 ) -> Option<GenericBound> {
     Some(match *bound {
         hir::GenericBound::Outlives(lt) => GenericBound::Outlives(clean_lifetime(lt, cx)),
-        hir::GenericBound::LangItemTrait(lang_item, span, _, generic_args) => {
-            let def_id = cx.tcx.require_lang_item(lang_item, Some(span));
-
-            let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(cx.tcx, def_id));
-
-            let generic_args = clean_generic_args(generic_args, cx);
-            let GenericArgs::AngleBracketed { bindings, .. } = generic_args else {
-                bug!("clean: parenthesized `GenericBound::LangItemTrait`");
-            };
-
-            let trait_ = clean_trait_ref_with_bindings(cx, trait_ref, bindings);
-            GenericBound::TraitBound(
-                PolyTrait { trait_, generic_params: vec![] },
-                hir::TraitBoundModifier::None,
-            )
-        }
         hir::GenericBound::Trait(ref t, modifier) => {
             // `T: ~const Destruct` is hidden because `T: Destruct` is a no-op.
             if modifier == hir::TraitBoundModifier::MaybeConst

src/tools/clippy/clippy_lints/src/len_zero.rs

@@ -8,8 +8,8 @@ use rustc_hir::def::Res;
 use rustc_hir::def_id::{DefId, DefIdSet};
 use rustc_hir::{
     AssocItemKind, BinOpKind, Expr, ExprKind, FnRetTy, GenericArg, GenericBound, ImplItem, ImplItemKind,
-    ImplicitSelfKind, Item, ItemKind, LangItem, Mutability, Node, PatKind, PathSegment, PrimTy, QPath, TraitItemRef,
-    TyKind, TypeBindingKind,
+    ImplicitSelfKind, Item, ItemKind, Mutability, Node, PatKind, PathSegment, PrimTy, QPath, TraitItemRef,
+    TyKind, TypeBindingKind, OpaqueTyOrigin,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{self, AssocKind, FnSig, Ty};
@@ -289,8 +289,10 @@ fn extract_future_output<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<&
             kind: ItemKind::OpaqueTy(opaque),
             ..
         } = item
-        && opaque.bounds.len() == 1
-        && let GenericBound::LangItemTrait(LangItem::Future, _, _, generic_args) = &opaque.bounds[0]
+        && let OpaqueTyOrigin::AsyncFn(_) = opaque.origin
+        && let [GenericBound::Trait(trait_ref, _)] = &opaque.bounds
+        && let Some(segment) = trait_ref.trait_ref.path.segments.last()
+        && let Some(generic_args) = segment.args
         && generic_args.bindings.len() == 1
         && let TypeBindingKind::Equality {
             term:

tests/ui/duplicate_entry_error.stderr

@@ -1,8 +1,11 @@
 error[E0152]: found duplicate lang item `panic_impl`
   --> $DIR/duplicate_entry_error.rs:11:1
    |
-LL | fn panic_impl(info: &PanicInfo) -> ! {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / fn panic_impl(info: &PanicInfo) -> ! {
+LL | |
+LL | |     loop {}
+LL | | }
+   | |_^
    |
    = note: the lang item is first defined in crate `std` (which `duplicate_entry_error` depends on)
    = note: first definition in `std` loaded from SYSROOT/libstd-*.rlib

tests/ui/error-codes/E0152.stderr

@@ -2,7 +2,7 @@ error[E0152]: found duplicate lang item `owned_box`
   --> $DIR/E0152.rs:5:1
    |
 LL | struct Foo<T>(T);
-   | ^^^^^^^^^^^^^
+   | ^^^^^^^^^^^^^^^^^
    |
    = note: the lang item is first defined in crate `alloc` (which `std` depends on)
    = note: first definition in `alloc` loaded from SYSROOT/liballoc-*.rlib

tests/ui/error-codes/E0264.stderr

@@ -2,7 +2,7 @@ error[E0264]: unknown external lang item: `cake`
   --> $DIR/E0264.rs:5:5
    |
 LL |     fn cake();
-   |     ^^^^^^^^^
+   |     ^^^^^^^^^^
 
 error: aborting due to 1 previous error
 

tests/ui/lang-items/lang-item-generic-requirements.rs

@@ -22,6 +22,8 @@ trait MyIndex<'a, T> {}
 #[lang = "phantom_data"]
 //~^ ERROR `phantom_data` language item must be applied to a struct with 1 generic argument
 struct MyPhantomData<T, U>;
+//~^ ERROR parameter `T` is never used
+//~| ERROR parameter `U` is never used
 
 #[lang = "owned_box"]
 //~^ ERROR `owned_box` language item must be applied to a struct with at least 1 generic argument
@@ -40,6 +42,7 @@ fn ice() {
     let r = 5;
     let a = 6;
     r + a;
+    //~^ ERROR cannot add `{integer}` to `{integer}`
 
     // Use drop in place
     my_ptr_drop();

tests/ui/lang-items/lang-item-generic-requirements.stderr

@@ -33,7 +33,7 @@ LL | struct MyPhantomData<T, U>;
    |                     ------ this struct has 2 generic arguments
 
 error[E0718]: `owned_box` language item must be applied to a struct with at least 1 generic argument
-  --> $DIR/lang-item-generic-requirements.rs:26:1
+  --> $DIR/lang-item-generic-requirements.rs:28:1
    |
 LL | #[lang = "owned_box"]
    | ^^^^^^^^^^^^^^^^^^^^^
@@ -42,14 +42,43 @@ LL | struct Foo;
    |           - this struct has 0 generic arguments
 
 error[E0718]: `start` language item must be applied to a function with 1 generic argument
-  --> $DIR/lang-item-generic-requirements.rs:32:1
+  --> $DIR/lang-item-generic-requirements.rs:34:1
    |
 LL | #[lang = "start"]
    | ^^^^^^^^^^^^^^^^^
 LL |
 LL | fn start(_: *const u8, _: isize, _: *const *const u8) -> isize {
    |         - this function has 0 generic arguments
 
-error: aborting due to 6 previous errors
+error[E0392]: parameter `T` is never used
+  --> $DIR/lang-item-generic-requirements.rs:24:22
+   |
+LL | struct MyPhantomData<T, U>;
+   |                      ^ unused parameter
+   |
+   = help: consider removing `T` or referring to it in a field
+   = help: if you intended `T` to be a const parameter, use `const T: usize` instead
+
+error[E0392]: parameter `U` is never used
+  --> $DIR/lang-item-generic-requirements.rs:24:25
+   |
+LL | struct MyPhantomData<T, U>;
+   |                         ^ unused parameter
+   |
+   = help: consider removing `U` or referring to it in a field
+   = help: if you intended `U` to be a const parameter, use `const U: usize` instead
+
+error[E0369]: cannot add `{integer}` to `{integer}`
+  --> $DIR/lang-item-generic-requirements.rs:44:7
+   |
+LL |     r + a;
+   |     - ^ - {integer}
+   |     |
+   |     {integer}
+
+error: requires `copy` lang_item
+
+error: aborting due to 10 previous errors
 
-For more information about this error, try `rustc --explain E0718`.
+Some errors have detailed explanations: E0369, E0392, E0718.
+For more information about an error, try `rustc --explain E0369`.

tests/ui/panic-handler/panic-handler-duplicate.stderr

@@ -1,14 +1,18 @@
 error[E0152]: found duplicate lang item `panic_impl`
   --> $DIR/panic-handler-duplicate.rs:15:1
    |
-LL | fn panic2(info: &PanicInfo) -> ! {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / fn panic2(info: &PanicInfo) -> ! {
+LL | |     loop {}
+LL | | }
+   | |_^
    |
 note: the lang item is first defined here
   --> $DIR/panic-handler-duplicate.rs:10:1
    |
-LL | fn panic(info: &PanicInfo) -> ! {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / fn panic(info: &PanicInfo) -> ! {
+LL | |     loop {}
+LL | | }
+   | |_^
 
 error: aborting due to 1 previous error
 

tests/ui/panic-handler/panic-handler-std.stderr

@@ -1,8 +1,10 @@
 error[E0152]: found duplicate lang item `panic_impl`
   --> $DIR/panic-handler-std.rs:8:1
    |
-LL | fn panic(info: PanicInfo) -> ! {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | / fn panic(info: PanicInfo) -> ! {
+LL | |     loop {}
+LL | | }
+   | |_^
    |
    = note: the lang item is first defined in crate `std` (which `panic_handler_std` depends on)
    = note: first definition in `std` loaded from SYSROOT/libstd-*.rlib

tests/ui/traits/issue-102989.rs

@@ -7,6 +7,7 @@ trait Sized { } //~ ERROR found duplicate lang item `sized`
 fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
     //~^ ERROR `self` parameter is only allowed in associated functions
     //~| ERROR cannot find type `Struct` in this scope
+    //~| ERROR mismatched types
     let x = x << 1;
     //~^ ERROR cannot find value `x` in this scope
 }

tests/ui/traits/issue-102989.stderr

@@ -13,7 +13,7 @@ LL | fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
    |                      ^^^^^^ not found in this scope
 
 error[E0425]: cannot find value `x` in this scope
-  --> $DIR/issue-102989.rs:10:13
+  --> $DIR/issue-102989.rs:11:13
    |
 LL |     let x = x << 1;
    |             ^ help: a local variable with a similar name exists: `f`
@@ -22,13 +22,27 @@ error[E0152]: found duplicate lang item `sized`
   --> $DIR/issue-102989.rs:5:1
    |
 LL | trait Sized { }
-   | ^^^^^^^^^^^
+   | ^^^^^^^^^^^^^^^
    |
    = note: the lang item is first defined in crate `core` (which `std` depends on)
    = note: first definition in `core` loaded from SYSROOT/libcore-*.rlib
    = note: second definition in the local crate (`issue_102989`)
 
-error: aborting due to 4 previous errors
+error[E0308]: mismatched types
+  --> $DIR/issue-102989.rs:7:42
+   |
+LL | fn ref_Struct(self: &Struct, f: &u32) -> &u32 {
+   |    ----------                            ^^^^ expected `&u32`, found `()`
+   |    |
+   |    implicitly returns `()` as its body has no tail or `return` expression
+   |
+help: consider returning the local binding `f`
+   |
+LL ~     let x = x << 1;
+LL +     f
+   |
+
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0152, E0412, E0425.
+Some errors have detailed explanations: E0152, E0308, E0412, E0425.
 For more information about an error, try `rustc --explain E0152`.