Move defs and bounds from Universal to LoweringContext

3 files changed, 60 insertions, 87 deletions

diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 12d1b8404eb..e12a3ad3b79 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -83,6 +83,8 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             task_context: None,
             current_item: None,
             captured_lifetimes: None,
+            impl_trait_defs: Vec::new(),
+            impl_trait_bounds: Vec::new(),
             allow_try_trait: Some([sym::try_trait_v2, sym::yeet_desugar_details][..].into()),
             allow_gen_future: Some([sym::gen_future][..].into()),
             allow_into_future: Some([sym::into_future][..].into()),
@@ -264,16 +266,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     let body_id =
                         this.lower_maybe_async_body(span, &decl, asyncness, body.as_deref());
 
-                    let (generics, decl) =
-                        this.add_implicit_generics(generics, id, |this, idty, idpb| {
-                            let ret_id = asyncness.opt_return_id();
-                            this.lower_fn_decl(
-                                &decl,
-                                Some((id, idty, idpb)),
-                                FnDeclKind::Fn,
-                                ret_id,
-                            )
-                        });
+                    let (generics, decl) = this.add_implicit_generics(generics, id, |this| {
+                        let ret_id = asyncness.opt_return_id();
+                        this.lower_fn_decl(&decl, Some(id), FnDeclKind::Fn, ret_id)
+                    });
                     let sig = hir::FnSig {
                         decl,
                         header: this.lower_fn_header(header),
@@ -387,7 +383,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 // lifetime to be added, but rather a reference to a
                 // parent lifetime.
                 let (generics, (trait_ref, lowered_ty)) =
-                    self.add_implicit_generics(ast_generics, id, |this, _, _| {
+                    self.add_implicit_generics(ast_generics, id, |this| {
                         let trait_ref = trait_ref.as_ref().map(|trait_ref| {
                             this.lower_trait_ref(
                                 trait_ref,
@@ -652,7 +648,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ForeignItemKind::Fn(box Fn { ref sig, ref generics, .. }) => {
                     let fdec = &sig.decl;
                     let (generics, (fn_dec, fn_args)) =
-                        self.add_implicit_generics(generics, i.id, |this, _, _| {
+                        self.add_implicit_generics(generics, i.id, |this| {
                             (
                                 // Disallow `impl Trait` in foreign items.
                                 this.lower_fn_decl(fdec, None, FnDeclKind::ExternFn, None),
@@ -1231,8 +1227,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         is_async: Option<NodeId>,
     ) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) {
         let header = self.lower_fn_header(sig.header);
-        let (generics, decl) = self.add_implicit_generics(generics, id, |this, idty, idpb| {
-            this.lower_fn_decl(&sig.decl, Some((id, idty, idpb)), kind, is_async)
+        let (generics, decl) = self.add_implicit_generics(generics, id, |this| {
+            this.lower_fn_decl(&sig.decl, Some(id), kind, is_async)
         });
         (generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
     }
@@ -1292,7 +1288,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     pub(super) fn lower_generics_mut(
         &mut self,
         generics: &Generics,
-        mut itctx: ImplTraitContext<'_, 'hir>,
+        mut itctx: ImplTraitContext,
     ) -> GenericsCtor<'hir> {
         // Error if `?Trait` bounds in where clauses don't refer directly to type parameters.
         // Note: we used to clone these bounds directly onto the type parameter (and avoid lowering
@@ -1372,7 +1368,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     pub(super) fn lower_generics(
         &mut self,
         generics: &Generics,
-        itctx: ImplTraitContext<'_, 'hir>,
+        itctx: ImplTraitContext,
     ) -> &'hir hir::Generics<'hir> {
         let generics_ctor = self.lower_generics_mut(generics, itctx);
         generics_ctor.into_generics(self.arena)
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index e59bc9aa6b3..fb846249103 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -121,6 +121,9 @@ struct LoweringContext<'a, 'hir: 'a> {
     local_id_to_def_id: SortedMap<ItemLocalId, LocalDefId>,
     trait_map: FxHashMap<ItemLocalId, Box<[TraitCandidate]>>,
 
+    impl_trait_defs: Vec<hir::GenericParam<'hir>>,
+    impl_trait_bounds: Vec<hir::WherePredicate<'hir>>,
+
     /// NodeIds that are lowered inside the current HIR owner.
     node_id_to_local_id: FxHashMap<NodeId, hir::ItemLocalId>,
 
@@ -244,13 +247,13 @@ pub trait ResolverAstLowering {
 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
 /// and if so, what meaning it has.
 #[derive(Debug)]
-enum ImplTraitContext<'b, 'a> {
+enum ImplTraitContext {
     /// Treat `impl Trait` as shorthand for a new universal generic parameter.
     /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
     /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
     ///
     /// Newly generated parameters should be inserted into the given `Vec`.
-    Universal(&'b mut Vec<hir::GenericParam<'a>>, &'b mut Vec<hir::WherePredicate<'a>>, LocalDefId),
+    Universal(LocalDefId),
 
     /// Treat `impl Trait` as shorthand for a new opaque type.
     /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
@@ -290,11 +293,11 @@ enum ImplTraitPosition {
     ImplReturn,
 }
 
-impl<'a> ImplTraitContext<'_, 'a> {
-    fn reborrow<'this>(&'this mut self) -> ImplTraitContext<'this, 'a> {
+impl ImplTraitContext {
+    fn reborrow<'this>(&'this mut self) -> ImplTraitContext {
         use self::ImplTraitContext::*;
         match self {
-            Universal(params, bounds, parent) => Universal(params, bounds, *parent),
+            Universal(parent) => Universal(*parent),
             ReturnPositionOpaqueTy { origin } => ReturnPositionOpaqueTy { origin: *origin },
             TypeAliasesOpaqueTy => TypeAliasesOpaqueTy,
             Disallowed(pos) => Disallowed(*pos),
@@ -701,34 +704,24 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         generics: &Generics,
         parent_node_id: NodeId,
-        f: impl FnOnce(
-            &mut Self,
-            &mut Vec<hir::GenericParam<'hir>>,
-            &mut Vec<hir::WherePredicate<'hir>>,
-        ) -> T,
+        f: impl FnOnce(&mut Self) -> T,
     ) -> (&'hir hir::Generics<'hir>, T) {
-        let mut impl_trait_defs = Vec::new();
-        let mut impl_trait_bounds = Vec::new();
-        let mut lowered_generics = self.lower_generics_mut(
-            generics,
-            ImplTraitContext::Universal(
-                &mut impl_trait_defs,
-                &mut impl_trait_bounds,
-                self.current_hir_id_owner,
-            ),
-        );
-        let res = f(self, &mut impl_trait_defs, &mut impl_trait_bounds);
+        let mut lowered_generics = self
+            .lower_generics_mut(generics, ImplTraitContext::Universal(self.current_hir_id_owner));
+        let res = f(self);
 
         let extra_lifetimes = self.resolver.take_extra_lifetime_params(parent_node_id);
+        let impl_trait_defs = std::mem::take(&mut self.impl_trait_defs);
         lowered_generics.params.extend(
             extra_lifetimes
                 .into_iter()
                 .filter_map(|(ident, node_id, res)| {
                     self.lifetime_res_to_generic_param(ident, node_id, res)
                 })
-                .chain(impl_trait_defs),
+                .chain(impl_trait_defs.into_iter()),
         );
-        lowered_generics.predicates.extend(impl_trait_bounds);
+        let impl_trait_bounds = std::mem::take(&mut self.impl_trait_bounds);
+        lowered_generics.predicates.extend(impl_trait_bounds.into_iter());
 
         let lowered_generics = lowered_generics.into_generics(self.arena);
         (lowered_generics, res)
@@ -898,7 +891,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_assoc_ty_constraint(
         &mut self,
         constraint: &AssocConstraint,
-        mut itctx: ImplTraitContext<'_, 'hir>,
+        mut itctx: ImplTraitContext,
     ) -> hir::TypeBinding<'hir> {
         debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
 
@@ -962,7 +955,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     // so desugar to
                     //
                     //     fn foo(x: dyn Iterator<Item = impl Debug>)
-                    ImplTraitContext::Universal(_, _, parent) if self.is_in_dyn_type => {
+                    ImplTraitContext::Universal(parent) if self.is_in_dyn_type => {
                         parent_def_id = parent;
                         (true, itctx)
                     }
@@ -1036,7 +1029,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_generic_arg(
         &mut self,
         arg: &ast::GenericArg,
-        itctx: ImplTraitContext<'_, 'hir>,
+        itctx: ImplTraitContext,
     ) -> hir::GenericArg<'hir> {
         match arg {
             ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(&lt)),
@@ -1103,7 +1096,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_, 'hir>) -> &'hir hir::Ty<'hir> {
+    fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext) -> &'hir hir::Ty<'hir> {
         self.arena.alloc(self.lower_ty_direct(t, itctx))
     }
 
@@ -1113,7 +1106,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         qself: &Option<QSelf>,
         path: &Path,
         param_mode: ParamMode,
-        itctx: ImplTraitContext<'_, 'hir>,
+        itctx: ImplTraitContext,
     ) -> hir::Ty<'hir> {
         let id = self.lower_node_id(t.id);
         let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
@@ -1128,7 +1121,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.ty(span, hir::TyKind::Tup(tys))
     }
 
-    fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_, 'hir>) -> hir::Ty<'hir> {
+    fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext) -> hir::Ty<'hir> {
         let kind = match t.kind {
             TyKind::Infer => hir::TyKind::Infer,
             TyKind::Err => hir::TyKind::Err,
@@ -1235,32 +1228,24 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             |this| this.lower_param_bounds(bounds, nested_itctx),
                         )
                     }
-                    ImplTraitContext::Universal(
-                        in_band_ty_params,
-                        in_band_ty_bounds,
-                        parent_def_id,
-                    ) => {
+                    ImplTraitContext::Universal(parent_def_id) => {
                         // Add a definition for the in-band `Param`.
                         let def_id = self.resolver.local_def_id(def_node_id);
 
-                        let hir_bounds = self.lower_param_bounds(
-                            bounds,
-                            ImplTraitContext::Universal(
-                                in_band_ty_params,
-                                in_band_ty_bounds,
-                                parent_def_id,
-                            ),
-                        );
+                        let hir_bounds = self
+                            .lower_param_bounds(bounds, ImplTraitContext::Universal(parent_def_id));
                         // Set the name to `impl Bound1 + Bound2`.
                         let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span);
-                        in_band_ty_params.push(hir::GenericParam {
+                        let param = hir::GenericParam {
                             hir_id: self.lower_node_id(def_node_id),
                             name: ParamName::Plain(self.lower_ident(ident)),
                             pure_wrt_drop: false,
                             span: self.lower_span(span),
                             kind: hir::GenericParamKind::Type { default: None, synthetic: true },
                             colon_span: None,
-                        });
+                        };
+                        self.impl_trait_defs.push(param);
+
                         if let Some(preds) = self.lower_generic_bound_predicate(
                             ident,
                             def_node_id,
@@ -1268,7 +1253,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             hir_bounds,
                             hir::PredicateOrigin::ImplTrait,
                         ) {
-                            in_band_ty_bounds.push(preds)
+                            self.impl_trait_bounds.push(preds)
                         }
 
                         hir::TyKind::Path(hir::QPath::Resolved(
@@ -1442,21 +1427,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_fn_decl(
         &mut self,
         decl: &FnDecl,
-        mut in_band_ty_params: Option<(
-            NodeId,
-            &mut Vec<hir::GenericParam<'hir>>,
-            &mut Vec<hir::WherePredicate<'hir>>,
-        )>,
+        fn_node_id: Option<NodeId>,
         kind: FnDeclKind,
         make_ret_async: Option<NodeId>,
     ) -> &'hir hir::FnDecl<'hir> {
         debug!(
             "lower_fn_decl(\
             fn_decl: {:?}, \
-            in_band_ty_params: {:?}, \
+            fn_node_id: {:?}, \
             kind: {:?}, \
             make_ret_async: {:?})",
-            decl, in_band_ty_params, kind, make_ret_async,
+            decl, fn_node_id, kind, make_ret_async,
         );
 
         let c_variadic = decl.c_variadic();
@@ -1469,10 +1450,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             inputs = &inputs[..inputs.len() - 1];
         }
         let inputs = self.arena.alloc_from_iter(inputs.iter().map(|param| {
-            if let Some((_, ibty, ibpb)) = &mut in_band_ty_params {
+            if fn_node_id.is_some() {
                 self.lower_ty_direct(
                     &param.ty,
-                    ImplTraitContext::Universal(ibty, ibpb, self.current_hir_id_owner),
+                    ImplTraitContext::Universal(self.current_hir_id_owner),
                 )
             } else {
                 self.lower_ty_direct(
@@ -1494,15 +1475,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let output = if let Some(ret_id) = make_ret_async {
             self.lower_async_fn_ret_ty(
                 &decl.output,
-                in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
+                fn_node_id.expect("`make_ret_async` but no `fn_def_id`"),
                 ret_id,
             )
         } else {
             match decl.output {
                 FnRetTy::Ty(ref ty) => {
-                    let context = match in_band_ty_params {
-                        Some((node_id, _, _)) if kind.impl_trait_return_allowed() => {
-                            let fn_def_id = self.resolver.local_def_id(node_id);
+                    let context = match fn_node_id {
+                        Some(fn_node_id) if kind.impl_trait_return_allowed() => {
+                            let fn_def_id = self.resolver.local_def_id(fn_node_id);
                             ImplTraitContext::ReturnPositionOpaqueTy {
                                 origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id),
                             }
@@ -1788,7 +1769,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_param_bound(
         &mut self,
         tpb: &GenericBound,
-        itctx: ImplTraitContext<'_, 'hir>,
+        itctx: ImplTraitContext,
     ) -> hir::GenericBound<'hir> {
         match tpb {
             GenericBound::Trait(p, modifier) => hir::GenericBound::Trait(
@@ -1966,11 +1947,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn lower_trait_ref(
-        &mut self,
-        p: &TraitRef,
-        itctx: ImplTraitContext<'_, 'hir>,
-    ) -> hir::TraitRef<'hir> {
+    fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext) -> hir::TraitRef<'hir> {
         let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
             hir::QPath::Resolved(None, path) => path,
             qpath => panic!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
@@ -1982,7 +1959,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_poly_trait_ref(
         &mut self,
         p: &PolyTraitRef,
-        mut itctx: ImplTraitContext<'_, 'hir>,
+        mut itctx: ImplTraitContext,
     ) -> hir::PolyTraitRef<'hir> {
         let bound_generic_params = self.lower_generic_params(&p.bound_generic_params);
 
@@ -1993,14 +1970,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         hir::PolyTraitRef { bound_generic_params, trait_ref, span: self.lower_span(p.span) }
     }
 
-    fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_, 'hir>) -> hir::MutTy<'hir> {
+    fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext) -> hir::MutTy<'hir> {
         hir::MutTy { ty: self.lower_ty(&mt.ty, itctx), mutbl: mt.mutbl }
     }
 
     fn lower_param_bounds(
         &mut self,
         bounds: &[GenericBound],
-        itctx: ImplTraitContext<'_, 'hir>,
+        itctx: ImplTraitContext,
     ) -> hir::GenericBounds<'hir> {
         self.arena.alloc_from_iter(self.lower_param_bounds_mut(bounds, itctx))
     }
@@ -2008,7 +1985,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_param_bounds_mut<'s>(
         &'s mut self,
         bounds: &'s [GenericBound],
-        mut itctx: ImplTraitContext<'s, 'hir>,
+        mut itctx: ImplTraitContext,
     ) -> impl Iterator<Item = hir::GenericBound<'hir>> + Captures<'s> + Captures<'a> {
         bounds.iter().map(move |bound| self.lower_param_bound(bound, itctx.reborrow()))
     }
diff --git a/compiler/rustc_ast_lowering/src/path.rs b/compiler/rustc_ast_lowering/src/path.rs
index 7fc8aac5116..0827fc8173e 100644
--- a/compiler/rustc_ast_lowering/src/path.rs
+++ b/compiler/rustc_ast_lowering/src/path.rs
@@ -21,7 +21,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         qself: &Option<QSelf>,
         p: &Path,
         param_mode: ParamMode,
-        mut itctx: ImplTraitContext<'_, 'hir>,
+        mut itctx: ImplTraitContext,
     ) -> hir::QPath<'hir> {
         debug!("lower_qpath(id: {:?}, qself: {:?}, p: {:?})", id, qself, p);
         let qself_position = qself.as_ref().map(|q| q.position);
@@ -180,7 +180,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         segment: &PathSegment,
         param_mode: ParamMode,
         parenthesized_generic_args: ParenthesizedGenericArgs,
-        itctx: ImplTraitContext<'_, 'hir>,
+        itctx: ImplTraitContext,
     ) -> hir::PathSegment<'hir> {
         debug!("path_span: {:?}, lower_path_segment(segment: {:?})", path_span, segment,);
         let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
@@ -318,7 +318,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         &mut self,
         data: &AngleBracketedArgs,
         param_mode: ParamMode,
-        mut itctx: ImplTraitContext<'_, 'hir>,
+        mut itctx: ImplTraitContext,
     ) -> (GenericArgsCtor<'hir>, bool) {
         let has_non_lt_args = data.args.iter().any(|arg| match arg {
             AngleBracketedArg::Arg(ast::GenericArg::Lifetime(_))