Use upvar_tys in more places, make it a list

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -886,6 +886,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
             .universal_regions()
             .defining_ty
             .upvar_tys()
+            .iter()
             .position(|ty| self.any_param_predicate_mentions(&predicates, ty, region))
         {
             let (upvar_name, upvar_span) = self.regioncx.get_upvar_name_and_span_for_region(

compiler/rustc_borrowck/src/diagnostics/var_name.rs

@@ -43,7 +43,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         fr: RegionVid,
     ) -> Option<usize> {
         let upvar_index =
-            self.universal_regions().defining_ty.upvar_tys().position(|upvar_ty| {
+            self.universal_regions().defining_ty.upvar_tys().iter().position(|upvar_ty| {
                 debug!("get_upvar_index_for_region: upvar_ty={upvar_ty:?}");
                 tcx.any_free_region_meets(&upvar_ty, |r| {
                     let r = r.as_var();
@@ -52,7 +52,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 })
             })?;
 
-        let upvar_ty = self.universal_regions().defining_ty.upvar_tys().nth(upvar_index);
+        let upvar_ty = self.universal_regions().defining_ty.upvar_tys().get(upvar_index);
 
         debug!(
             "get_upvar_index_for_region: found {fr:?} in upvar {upvar_index} which has type {upvar_ty:?}",

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -791,25 +791,20 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                     (adt_def.variant(FIRST_VARIANT), args)
                 }
                 ty::Closure(_, args) => {
-                    return match args
-                        .as_closure()
-                        .tupled_upvars_ty()
-                        .tuple_fields()
-                        .get(field.index())
-                    {
+                    return match args.as_closure().upvar_tys().get(field.index()) {
                         Some(&ty) => Ok(ty),
                         None => Err(FieldAccessError::OutOfRange {
-                            field_count: args.as_closure().upvar_tys().count(),
+                            field_count: args.as_closure().upvar_tys().len(),
                         }),
                     };
                 }
                 ty::Generator(_, args, _) => {
                     // Only prefix fields (upvars and current state) are
                     // accessible without a variant index.
-                    return match args.as_generator().prefix_tys().nth(field.index()) {
-                        Some(ty) => Ok(ty),
+                    return match args.as_generator().prefix_tys().get(field.index()) {
+                        Some(ty) => Ok(*ty),
                         None => Err(FieldAccessError::OutOfRange {
-                            field_count: args.as_generator().prefix_tys().count(),
+                            field_count: args.as_generator().prefix_tys().len(),
                         }),
                     };
                 }
@@ -1772,10 +1767,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
             }
             AggregateKind::Closure(_, args) => {
-                match args.as_closure().upvar_tys().nth(field_index.as_usize()) {
-                    Some(ty) => Ok(ty),
+                match args.as_closure().upvar_tys().get(field_index.as_usize()) {
+                    Some(ty) => Ok(*ty),
                     None => Err(FieldAccessError::OutOfRange {
-                        field_count: args.as_closure().upvar_tys().count(),
+                        field_count: args.as_closure().upvar_tys().len(),
                     }),
                 }
             }
@@ -1783,10 +1778,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // It doesn't make sense to look at a field beyond the prefix;
                 // these require a variant index, and are not initialized in
                 // aggregate rvalues.
-                match args.as_generator().prefix_tys().nth(field_index.as_usize()) {
-                    Some(ty) => Ok(ty),
+                match args.as_generator().prefix_tys().get(field_index.as_usize()) {
+                    Some(ty) => Ok(*ty),
                     None => Err(FieldAccessError::OutOfRange {
-                        field_count: args.as_generator().prefix_tys().count(),
+                        field_count: args.as_generator().prefix_tys().len(),
                     }),
                 }
             }

compiler/rustc_borrowck/src/universal_regions.rs

@@ -12,7 +12,6 @@
 //! The code in this file doesn't *do anything* with those results; it
 //! just returns them for other code to use.
 
-use either::Either;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::Diagnostic;
 use rustc_hir as hir;
@@ -115,14 +114,12 @@ impl<'tcx> DefiningTy<'tcx> {
     /// not a closure or generator, there are no upvars, and hence it
     /// will be an empty list. The order of types in this list will
     /// match up with the upvar order in the HIR, typesystem, and MIR.
-    pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
+    pub fn upvar_tys(self) -> &'tcx ty::List<Ty<'tcx>> {
         match self {
-            DefiningTy::Closure(_, args) => Either::Left(args.as_closure().upvar_tys()),
-            DefiningTy::Generator(_, args, _) => {
-                Either::Right(Either::Left(args.as_generator().upvar_tys()))
-            }
+            DefiningTy::Closure(_, args) => args.as_closure().upvar_tys(),
+            DefiningTy::Generator(_, args, _) => args.as_generator().upvar_tys(),
             DefiningTy::FnDef(..) | DefiningTy::Const(..) | DefiningTy::InlineConst(..) => {
-                Either::Right(Either::Right(iter::empty()))
+                ty::List::empty()
             }
         }
     }

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -990,14 +990,8 @@ fn build_upvar_field_di_nodes<'ll, 'tcx>(
     closure_or_generator_di_node: &'ll DIType,
 ) -> SmallVec<&'ll DIType> {
     let (&def_id, up_var_tys) = match closure_or_generator_ty.kind() {
-        ty::Generator(def_id, args, _) => {
-            let upvar_tys: SmallVec<_> = args.as_generator().prefix_tys().collect();
-            (def_id, upvar_tys)
-        }
-        ty::Closure(def_id, args) => {
-            let upvar_tys: SmallVec<_> = args.as_closure().upvar_tys().collect();
-            (def_id, upvar_tys)
-        }
+        ty::Generator(def_id, args, _) => (def_id, args.as_generator().prefix_tys()),
+        ty::Closure(def_id, args) => (def_id, args.as_closure().upvar_tys()),
         _ => {
             bug!(
                 "build_upvar_field_di_nodes() called with non-closure-or-generator-type: {:?}",
@@ -1007,9 +1001,7 @@ fn build_upvar_field_di_nodes<'ll, 'tcx>(
     };
 
     debug_assert!(
-        up_var_tys
-            .iter()
-            .all(|&t| t == cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), t))
+        up_var_tys.iter().all(|t| t == cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), t))
     );
 
     let capture_names = cx.tcx.closure_saved_names_of_captured_variables(def_id);

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs

@@ -379,6 +379,7 @@ pub fn build_generator_variant_struct_type_di_node<'ll, 'tcx>(
             // Fields that are common to all states
             let common_fields: SmallVec<_> = generator_args
                 .prefix_tys()
+                .iter()
                 .zip(common_upvar_names)
                 .enumerate()
                 .map(|(index, (upvar_ty, upvar_name))| {

compiler/rustc_const_eval/src/transform/validate.rs

@@ -630,7 +630,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     }
                     ty::Closure(_, args) => {
                         let args = args.as_closure();
-                        let Some(f_ty) = args.upvar_tys().nth(f.as_usize()) else {
+                        let Some(&f_ty) = args.upvar_tys().get(f.as_usize()) else {
                             fail_out_of_bounds(self, location);
                             return;
                         };
@@ -667,7 +667,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
 
                             f_ty.ty
                         } else {
-                            let Some(f_ty) = args.as_generator().prefix_tys().nth(f.index()) else {
+                            let Some(&f_ty) = args.as_generator().prefix_tys().get(f.index())
+                            else {
                                 fail_out_of_bounds(self, location);
                                 return;
                             };

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -448,7 +448,9 @@ where
             ty::Closure(_, ref args) => {
                 // Skip lifetime parameters of the enclosing item(s)
 
-                args.as_closure().tupled_upvars_ty().visit_with(self);
+                for upvar in args.as_closure().upvar_tys() {
+                    upvar.visit_with(self);
+                }
                 args.as_closure().sig_as_fn_ptr_ty().visit_with(self);
             }
 
@@ -456,7 +458,9 @@ where
                 // Skip lifetime parameters of the enclosing item(s)
                 // Also skip the witness type, because that has no free regions.
 
-                args.as_generator().tupled_upvars_ty().visit_with(self);
+                for upvar in args.as_generator().upvar_tys() {
+                    upvar.visit_with(self);
+                }
                 args.as_generator().return_ty().visit_with(self);
                 args.as_generator().yield_ty().visit_with(self);
                 args.as_generator().resume_ty().visit_with(self);

compiler/rustc_middle/src/ty/layout.rs

@@ -911,7 +911,7 @@ where
                         if i == tag_field {
                             return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
                         }
-                        TyMaybeWithLayout::Ty(args.as_generator().prefix_tys().nth(i).unwrap())
+                        TyMaybeWithLayout::Ty(args.as_generator().prefix_tys()[i])
                     }
                 },
 

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -827,7 +827,7 @@ pub trait PrettyPrinter<'tcx>:
                     if !args.as_generator().is_valid() {
                         p!("unavailable");
                     } else {
-                        self = self.comma_sep(args.as_generator().upvar_tys())?;
+                        self = self.comma_sep(args.as_generator().upvar_tys().iter())?;
                     }
                     p!(")");
 
@@ -900,7 +900,7 @@ pub trait PrettyPrinter<'tcx>:
                             print(args.as_closure().sig_as_fn_ptr_ty())
                         );
                         p!(" upvar_tys=(");
-                        self = self.comma_sep(args.as_closure().upvar_tys())?;
+                        self = self.comma_sep(args.as_closure().upvar_tys().iter())?;
                         p!(")");
                     }
                 }

compiler/rustc_middle/src/ty/sty.rs

@@ -296,15 +296,13 @@ impl<'tcx> ClosureArgs<'tcx> {
     /// In case there was a type error in figuring out the types of the captured path, an
     /// empty iterator is returned.
     #[inline]
-    pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
+    pub fn upvar_tys(self) -> &'tcx List<Ty<'tcx>> {
         match self.tupled_upvars_ty().kind() {
-            TyKind::Error(_) => None,
-            TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
+            TyKind::Error(_) => ty::List::empty(),
+            TyKind::Tuple(..) => self.tupled_upvars_ty().tuple_fields(),
             TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
             ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
         }
-        .into_iter()
-        .flatten()
     }
 
     /// Returns the tuple type representing the upvars for this closure.
@@ -436,15 +434,13 @@ impl<'tcx> GeneratorArgs<'tcx> {
     /// In case there was a type error in figuring out the types of the captured path, an
     /// empty iterator is returned.
     #[inline]
-    pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
+    pub fn upvar_tys(self) -> &'tcx List<Ty<'tcx>> {
         match self.tupled_upvars_ty().kind() {
-            TyKind::Error(_) => None,
-            TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
+            TyKind::Error(_) => ty::List::empty(),
+            TyKind::Tuple(..) => self.tupled_upvars_ty().tuple_fields(),
             TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
             ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
         }
-        .into_iter()
-        .flatten()
     }
 
     /// Returns the tuple type representing the upvars for this generator.
@@ -576,7 +572,7 @@ impl<'tcx> GeneratorArgs<'tcx> {
     /// This is the types of the fields of a generator which are not stored in a
     /// variant.
     #[inline]
-    pub fn prefix_tys(self) -> impl Iterator<Item = Ty<'tcx>> {
+    pub fn prefix_tys(self) -> &'tcx List<Ty<'tcx>> {
         self.upvar_tys()
     }
 }
@@ -592,20 +588,18 @@ impl<'tcx> UpvarArgs<'tcx> {
     /// In case there was a type error in figuring out the types of the captured path, an
     /// empty iterator is returned.
     #[inline]
-    pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
+    pub fn upvar_tys(self) -> &'tcx List<Ty<'tcx>> {
         let tupled_tys = match self {
             UpvarArgs::Closure(args) => args.as_closure().tupled_upvars_ty(),
             UpvarArgs::Generator(args) => args.as_generator().tupled_upvars_ty(),
         };
 
         match tupled_tys.kind() {
-            TyKind::Error(_) => None,
-            TyKind::Tuple(..) => Some(self.tupled_upvars_ty().tuple_fields()),
+            TyKind::Error(_) => ty::List::empty(),
+            TyKind::Tuple(..) => self.tupled_upvars_ty().tuple_fields(),
             TyKind::Infer(_) => bug!("upvar_tys called before capture types are inferred"),
             ty => bug!("Unexpected representation of upvar types tuple {:?}", ty),
         }
-        .into_iter()
-        .flatten()
     }
 
     #[inline]

compiler/rustc_mir_dataflow/src/elaborate_drops.rs

@@ -860,20 +860,14 @@ where
     fn open_drop(&mut self) -> BasicBlock {
         let ty = self.place_ty(self.place);
         match ty.kind() {
-            ty::Closure(_, args) => {
-                let tys: Vec<_> = args.as_closure().upvar_tys().collect();
-                self.open_drop_for_tuple(&tys)
-            }
+            ty::Closure(_, args) => self.open_drop_for_tuple(&args.as_closure().upvar_tys()),
             // Note that `elaborate_drops` only drops the upvars of a generator,
             // and this is ok because `open_drop` here can only be reached
             // within that own generator's resume function.
             // This should only happen for the self argument on the resume function.
             // It effectively only contains upvars until the generator transformation runs.
             // See librustc_body/transform/generator.rs for more details.
-            ty::Generator(_, args, _) => {
-                let tys: Vec<_> = args.as_generator().upvar_tys().collect();
-                self.open_drop_for_tuple(&tys)
-            }
+            ty::Generator(_, args, _) => self.open_drop_for_tuple(&args.as_generator().upvar_tys()),
             ty::Tuple(fields) => self.open_drop_for_tuple(fields),
             ty::Adt(def, args) => self.open_drop_for_adt(*def, args),
             ty::Dynamic(..) => self.complete_drop(self.succ, self.unwind),

compiler/rustc_mir_transform/src/generator.rs

@@ -856,7 +856,7 @@ fn sanitize_witness<'tcx>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
     witness: Ty<'tcx>,
-    upvars: Vec<Ty<'tcx>>,
+    upvars: &'tcx ty::List<Ty<'tcx>>,
     layout: &GeneratorLayout<'tcx>,
 ) {
     let did = body.source.def_id();
@@ -1471,7 +1471,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
                 let args = args.as_generator();
                 (
                     args.discr_ty(tcx),
-                    args.upvar_tys().collect::<Vec<_>>(),
+                    args.upvar_tys(),
                     args.witness(),
                     movability == hir::Movability::Movable,
                 )

compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs

@@ -291,9 +291,9 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
                 return Err(NoSolution);
             }
 
-            constraints.outlives.extend(
-                args.as_generator().upvar_tys().map(|t| -> ty::GenericArg<'tcx> { t.into() }),
-            );
+            constraints
+                .outlives
+                .extend(args.as_generator().upvar_tys().iter().map(ty::GenericArg::from));
             constraints.outlives.push(args.as_generator().resume_ty().into());
         }
 

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2169,7 +2169,8 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                         let all = args
                             .as_generator()
                             .upvar_tys()
-                            .chain(iter::once(args.as_generator().witness()))
+                            .iter()
+                            .chain([args.as_generator().witness()])
                             .collect::<Vec<_>>();
                         Where(obligation.predicate.rebind(all))
                     }
@@ -2210,7 +2211,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                     // Not yet resolved.
                     Ambiguous
                 } else {
-                    Where(obligation.predicate.rebind(args.as_closure().upvar_tys().collect()))
+                    Where(obligation.predicate.rebind(args.as_closure().upvar_tys().to_vec()))
                 }
             }
 

compiler/rustc_ty_utils/src/layout.rs

@@ -317,7 +317,9 @@ fn layout_of_uncached<'tcx>(
         ty::Closure(_, ref args) => {
             let tys = args.as_closure().upvar_tys();
             univariant(
-                &tys.map(|ty| Ok(cx.layout_of(ty)?.layout)).try_collect::<IndexVec<_, _>>()?,
+                &tys.iter()
+                    .map(|ty| Ok(cx.layout_of(ty)?.layout))
+                    .try_collect::<IndexVec<_, _>>()?,
                 &ReprOptions::default(),
                 StructKind::AlwaysSized,
             )?
@@ -729,7 +731,7 @@ fn generator_layout<'tcx>(
     // Build a prefix layout, including "promoting" all ineligible
     // locals as part of the prefix. We compute the layout of all of
     // these fields at once to get optimal packing.
-    let tag_index = args.as_generator().prefix_tys().count();
+    let tag_index = args.as_generator().prefix_tys().len();
 
     // `info.variant_fields` already accounts for the reserved variants, so no need to add them.
     let max_discr = (info.variant_fields.len() - 1) as u128;
@@ -748,6 +750,7 @@ fn generator_layout<'tcx>(
     let prefix_layouts = args
         .as_generator()
         .prefix_tys()
+        .iter()
         .map(|ty| Ok(cx.layout_of(ty)?.layout))
         .chain(iter::once(Ok(tag_layout)))
         .chain(promoted_layouts)
@@ -1062,6 +1065,7 @@ fn variant_info_for_generator<'tcx>(
     let upvar_fields: Vec<_> = args
         .as_generator()
         .upvar_tys()
+        .iter()
         .zip(upvar_names)
         .enumerate()
         .map(|(field_idx, (_, name))| {

compiler/rustc_ty_utils/src/needs_drop.rs

@@ -120,12 +120,16 @@ where
                     _ if component.is_copy_modulo_regions(tcx, self.param_env) => (),
 
                     ty::Closure(_, args) => {
-                        queue_type(self, args.as_closure().tupled_upvars_ty());
+                        for upvar in args.as_closure().upvar_tys() {
+                            queue_type(self, upvar);
+                        }
                     }
 
                     ty::Generator(def_id, args, _) => {
                         let args = args.as_generator();
-                        queue_type(self, args.tupled_upvars_ty());
+                        for upvar in args.upvar_tys() {
+                            queue_type(self, upvar);
+                        }
 
                         let witness = args.witness();
                         let interior_tys = match witness.kind() {