diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 1ec1f0cb110..004b945eada 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2589,7 +2589,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             DefKind::InlineConst => substs.as_inline_const().parent_substs(),
             other => bug!("unexpected item {:?}", other),
         };
-        let parent_substs = tcx.mk_substs(parent_substs.iter());
+        let parent_substs = tcx.intern_substs(parent_substs);
 
         assert_eq!(typeck_root_substs.len(), parent_substs.len());
         if let Err(_) = self.eq_substs(
diff --git a/compiler/rustc_codegen_cranelift/src/codegen_i128.rs b/compiler/rustc_codegen_cranelift/src/codegen_i128.rs
index 638b2d573b5..b4a2537b5ea 100644
--- a/compiler/rustc_codegen_cranelift/src/codegen_i128.rs
+++ b/compiler/rustc_codegen_cranelift/src/codegen_i128.rs
@@ -56,7 +56,7 @@ pub(crate) fn maybe_codegen<'tcx>(
                     Some(fx.easy_call("__multi3", &[lhs, rhs], val_ty))
                 }
             } else {
-                let out_ty = fx.tcx.mk_tup([lhs.layout().ty, fx.tcx.types.bool].iter());
+                let out_ty = fx.tcx.intern_tup(&[lhs.layout().ty, fx.tcx.types.bool]);
                 let oflow = CPlace::new_stack_slot(fx, fx.layout_of(fx.tcx.types.i32));
                 let lhs = lhs.load_scalar(fx);
                 let rhs = rhs.load_scalar(fx);
@@ -78,7 +78,7 @@ pub(crate) fn maybe_codegen<'tcx>(
         }
         BinOp::Add | BinOp::Sub | BinOp::Mul => {
             assert!(checked);
-            let out_ty = fx.tcx.mk_tup([lhs.layout().ty, fx.tcx.types.bool].iter());
+            let out_ty = fx.tcx.intern_tup(&[lhs.layout().ty, fx.tcx.types.bool]);
             let out_place = CPlace::new_stack_slot(fx, fx.layout_of(out_ty));
             let (param_types, args) = if fx.tcx.sess.target.is_like_windows {
                 let (lhs_ptr, lhs_extra) = lhs.force_stack(fx);
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs
index d2ae6978ca2..cbac2e66765 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs
@@ -191,7 +191,7 @@ fn llvm_add_sub<'tcx>(
     // carry0 | carry1 -> carry or borrow respectively
     let cb_out = fx.bcx.ins().bor(cb0, cb1);
 
-    let layout = fx.layout_of(fx.tcx.mk_tup([fx.tcx.types.u8, fx.tcx.types.u64].iter()));
+    let layout = fx.layout_of(fx.tcx.intern_tup(&[fx.tcx.types.u8, fx.tcx.types.u64]));
     let val = CValue::by_val_pair(cb_out, c, layout);
     ret.write_cvalue(fx, val);
 }
diff --git a/compiler/rustc_codegen_cranelift/src/main_shim.rs b/compiler/rustc_codegen_cranelift/src/main_shim.rs
index 3e3b6857134..26327107df4 100644
--- a/compiler/rustc_codegen_cranelift/src/main_shim.rs
+++ b/compiler/rustc_codegen_cranelift/src/main_shim.rs
@@ -119,7 +119,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     tcx,
                     ParamEnv::reveal_all(),
                     report.def_id,
-                    tcx.mk_substs([GenericArg::from(main_ret_ty)].iter()),
+                    tcx.intern_substs(&[GenericArg::from(main_ret_ty)]),
                 )
                 .unwrap()
                 .unwrap()
diff --git a/compiler/rustc_codegen_cranelift/src/num.rs b/compiler/rustc_codegen_cranelift/src/num.rs
index afacbec6445..05905a7bcdf 100644
--- a/compiler/rustc_codegen_cranelift/src/num.rs
+++ b/compiler/rustc_codegen_cranelift/src/num.rs
@@ -289,7 +289,7 @@ pub(crate) fn codegen_checked_int_binop<'tcx>(
         _ => bug!("binop {:?} on checked int/uint lhs: {:?} rhs: {:?}", bin_op, in_lhs, in_rhs),
     };
 
-    let out_layout = fx.layout_of(fx.tcx.mk_tup([in_lhs.layout().ty, fx.tcx.types.bool].iter()));
+    let out_layout = fx.layout_of(fx.tcx.intern_tup(&[in_lhs.layout().ty, fx.tcx.types.bool]));
     CValue::by_val_pair(res, has_overflow, out_layout)
 }
 
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs b/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
index ec5707505c8..f6a3937870e 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
@@ -96,7 +96,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let loc_ty = self
             .tcx
             .type_of(self.tcx.require_lang_item(LangItem::PanicLocation, None))
-            .subst(*self.tcx, self.tcx.mk_substs([self.tcx.lifetimes.re_erased.into()].iter()));
+            .subst(*self.tcx, self.tcx.intern_substs(&[self.tcx.lifetimes.re_erased.into()]));
         let loc_layout = self.layout_of(loc_ty).unwrap();
         let location = self.allocate(loc_layout, MemoryKind::CallerLocation).unwrap();
 
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index 82562ac75e1..51700cf846b 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -378,7 +378,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
                 (
                     1,
                     vec![tcx.mk_imm_ref(tcx.mk_re_late_bound(ty::INNERMOST, br), param(0))],
-                    tcx.mk_projection(discriminant_def_id, tcx.mk_substs([param(0).into()].iter())),
+                    tcx.mk_projection(discriminant_def_id, tcx.intern_substs(&[param(0).into()])),
                 )
             }
 
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index e12a575d5ac..7c8abb4186f 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -301,7 +301,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Build a tuple (U0..Un) of the final upvar types U0..Un
         // and unify the upvar tuple type in the closure with it:
-        let final_tupled_upvars_type = self.tcx.mk_tup(final_upvar_tys.iter());
+        let final_tupled_upvars_type = self.tcx.intern_tup(&final_upvar_tys);
         self.demand_suptype(span, substs.tupled_upvars_ty(), final_tupled_upvars_type);
 
         let fake_reads = delegate
@@ -315,8 +315,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.typeck_results.borrow_mut().closure_size_eval.insert(
                 closure_def_id,
                 ClosureSizeProfileData {
-                    before_feature_tys: self.tcx.mk_tup(before_feature_tys.into_iter()),
-                    after_feature_tys: self.tcx.mk_tup(after_feature_tys.into_iter()),
+                    before_feature_tys: self.tcx.intern_tup(&before_feature_tys),
+                    after_feature_tys: self.tcx.intern_tup(&after_feature_tys),
                 },
             );
         }
diff --git a/compiler/rustc_metadata/src/native_libs.rs b/compiler/rustc_metadata/src/native_libs.rs
index ffb52d167b1..d823989bb02 100644
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@@ -502,7 +502,7 @@ impl<'tcx> Collector<'tcx> {
                 .subst_identity()
                 .fn_sig(self.tcx)
                 .inputs()
-                .map_bound(|slice| self.tcx.mk_type_list(slice.iter())),
+                .map_bound(|slice| self.tcx.intern_type_list(slice)),
         );
 
         argument_types
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index f955b312b23..46184cddd51 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -2525,14 +2525,12 @@ impl<'tcx> ConstantKind<'tcx> {
         }
 
         let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
-        let parent_substs = if let Some(parent_hir_id) = tcx.hir().opt_parent_id(hir_id) {
-            if let Some(parent_did) = parent_hir_id.as_owner() {
-                InternalSubsts::identity_for_item(tcx, parent_did.to_def_id())
-            } else {
-                tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
-            }
+        let parent_substs = if let Some(parent_hir_id) = tcx.hir().opt_parent_id(hir_id)
+            && let Some(parent_did) = parent_hir_id.as_owner()
+        {
+            InternalSubsts::identity_for_item(tcx, parent_did.to_def_id())
         } else {
-            tcx.mk_substs(Vec::<GenericArg<'tcx>>::new().into_iter())
+            tcx.intern_substs(&[])
         };
         debug!(?parent_substs);
 
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 117f3decd1a..79879ea20ab 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1190,7 +1190,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self.mk_imm_ref(
             self.lifetimes.re_static,
             self.type_of(self.require_lang_item(LangItem::PanicLocation, None))
-                .subst(self, self.mk_substs([self.lifetimes.re_static.into()].iter())),
+                .subst(self, self.intern_substs(&[self.lifetimes.re_static.into()])),
         )
     }
 
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index 1d76f435e26..3d0f9a5053c 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -686,7 +686,7 @@ where
                         Increase this counter if you tried to implement this but
                         failed to do it without duplicating a lot of code from
                         other places in the compiler: 2
-                        tcx.mk_tup(&[
+                        tcx.intern_tup(&[
                             tcx.mk_array(tcx.types.usize, 3),
                             tcx.mk_array(Option<fn()>),
                         ])
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 322afeb2d34..2ba25e8bfad 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -673,7 +673,7 @@ pub fn super_relate_consts<'tcx, R: TypeRelation<'tcx>>(
                     for (a_arg, b_arg) in aa.iter().zip(ba.iter()) {
                         related_args.push(r.consts(a_arg, b_arg)?);
                     }
-                    let related_args = tcx.mk_const_list(related_args.iter());
+                    let related_args = tcx.intern_const_list(&related_args);
                     Expr::FunctionCall(func, related_args)
                 }
                 _ => return Err(TypeError::ConstMismatch(expected_found(r, a, b))),
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 97ee2b1fc5d..9c1a6f716d0 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -418,7 +418,7 @@ impl<'tcx> ir::TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ty::PolyExistential
 
 impl<'tcx> ir::TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<ty::Const<'tcx>> {
     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_const_list(v.iter()))
+        ty::util::fold_list(self, folder, |tcx, v| tcx.intern_const_list(v))
     }
 }
 
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index 7f388b065ad..682ad081f5c 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -597,7 +597,7 @@ fn build_call_shim<'tcx>(
         let untuple_args = sig.inputs();
 
         // Create substitutions for the `Self` and `Args` generic parameters of the shim body.
-        let arg_tup = tcx.mk_tup(untuple_args.iter());
+        let arg_tup = tcx.intern_tup(untuple_args);
 
         (Some([ty.into(), arg_tup.into()]), Some(untuple_args))
     } else {
diff --git a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
index 949ef04dd4d..fb8695e7eaf 100644
--- a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
+++ b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
@@ -813,21 +813,18 @@ fn transform_substs<'tcx>(
     substs: SubstsRef<'tcx>,
     options: TransformTyOptions,
 ) -> SubstsRef<'tcx> {
-    let substs: Vec<GenericArg<'tcx>> = substs
-        .iter()
-        .map(|subst| {
-            if let GenericArgKind::Type(ty) = subst.unpack() {
-                if is_c_void_ty(tcx, ty) {
-                    tcx.mk_unit().into()
-                } else {
-                    transform_ty(tcx, ty, options).into()
-                }
+    let substs = substs.iter().map(|subst| {
+        if let GenericArgKind::Type(ty) = subst.unpack() {
+            if is_c_void_ty(tcx, ty) {
+                tcx.mk_unit().into()
             } else {
-                subst
+                transform_ty(tcx, ty, options).into()
             }
-        })
-        .collect();
-    tcx.mk_substs(substs.iter())
+        } else {
+            subst
+        }
+    });
+    tcx.mk_substs(substs)
 }
 
 /// Returns a type metadata identifier for the specified FnAbi using the Itanium C++ ABI with vendor
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs b/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs
index b6847b976be..3662463178f 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals/structural_traits.rs
@@ -191,10 +191,10 @@ pub(crate) fn extract_tupled_inputs_and_output_from_callable<'tcx>(
         ty::FnDef(def_id, substs) => Ok(Some(
             tcx.fn_sig(def_id)
                 .subst(tcx, substs)
-                .map_bound(|sig| (tcx.mk_tup(sig.inputs().iter()), sig.output())),
+                .map_bound(|sig| (tcx.intern_tup(sig.inputs()), sig.output())),
         )),
         ty::FnPtr(sig) => {
-            Ok(Some(sig.map_bound(|sig| (tcx.mk_tup(sig.inputs().iter()), sig.output()))))
+            Ok(Some(sig.map_bound(|sig| (tcx.intern_tup(sig.inputs()), sig.output()))))
         }
         ty::Closure(_, substs) => {
             let closure_substs = substs.as_closure();
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 011fe742a69..9143d28b8ee 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1923,7 +1923,7 @@ fn confirm_builtin_candidate<'cx, 'tcx>(
 ) -> Progress<'tcx> {
     let tcx = selcx.tcx();
     let self_ty = obligation.predicate.self_ty();
-    let substs = tcx.mk_substs([self_ty.into()].iter());
+    let substs = tcx.intern_substs(&[self_ty.into()]);
     let lang_items = tcx.lang_items();
     let item_def_id = obligation.predicate.def_id;
     let trait_def_id = tcx.trait_of_item(item_def_id).unwrap();
diff --git a/compiler/rustc_ty_utils/src/consts.rs b/compiler/rustc_ty_utils/src/consts.rs
index a9fbad55dac..852156c24f4 100644
--- a/compiler/rustc_ty_utils/src/consts.rs
+++ b/compiler/rustc_ty_utils/src/consts.rs
@@ -144,7 +144,7 @@ fn recurse_build<'tcx>(
             for &id in args.iter() {
                 new_args.push(recurse_build(tcx, body, id, root_span)?);
             }
-            let new_args = tcx.mk_const_list(new_args.iter());
+            let new_args = tcx.intern_const_list(&new_args);
             tcx.mk_const(Expr::FunctionCall(fun, new_args), node.ty)
         }
         &ExprKind::Binary { op, lhs, rhs } if check_binop(op) => {
diff --git a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
index 82d3b830d4f..8ddbacc3d7a 100644
--- a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
@@ -173,7 +173,7 @@ fn is_contains_sig(cx: &LateContext<'_>, call_id: HirId, iter_expr: &Expr<'_>) -
         && let Some(iter_item) = cx.tcx
             .associated_items(iter_trait)
             .find_by_name_and_kind(cx.tcx, Ident::with_dummy_span(Symbol::intern("Item")), AssocKind::Type, iter_trait)
-        && let substs = cx.tcx.mk_substs([GenericArg::from(typeck.expr_ty_adjusted(iter_expr))].into_iter())
+        && let substs = cx.tcx.intern_substs(&[GenericArg::from(typeck.expr_ty_adjusted(iter_expr))])
         && let proj_ty = cx.tcx.mk_projection(iter_item.def_id, substs)
         && let Ok(item_ty) = cx.tcx.try_normalize_erasing_regions(cx.param_env, proj_ty)
     {