diff --git a/src/librustc_arena/lib.rs b/src/librustc_arena/lib.rs
index 5cf4f97fb88..5e6a0340d12 100644
--- a/src/librustc_arena/lib.rs
+++ b/src/librustc_arena/lib.rs
@@ -611,11 +611,7 @@ macro_rules! which_arena_for_type {
 
 #[macro_export]
 macro_rules! declare_arena {
-    // This macro has to take the same input as
-    // `impl_arena_allocatable_decoders` which requires a second version of
-    // each type. We ignore that type until we can fix
-    // `impl_arena_allocatable_decoders`.
-    ([], [$($a:tt $name:ident: $ty:ty, $_gen_ty:ty;)*], $tcx:lifetime) => {
+    ([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
         #[derive(Default)]
         pub struct Arena<$tcx> {
             pub dropless: $crate::DroplessArena,
diff --git a/src/librustc_hir/arena.rs b/src/librustc_hir/arena.rs
index f439db71531..6ba39666607 100644
--- a/src/librustc_hir/arena.rs
+++ b/src/librustc_hir/arena.rs
@@ -12,41 +12,41 @@ macro_rules! arena_types {
     ($macro:path, $args:tt, $tcx:lifetime) => (
         $macro!($args, [
             // HIR types
-            [few] hir_krate: rustc_hir::Crate<$tcx>, rustc_hir::Crate<'_x>;
-            [] arm: rustc_hir::Arm<$tcx>, rustc_hir::Arm<'_x>;
-            [] asm_operand: rustc_hir::InlineAsmOperand<$tcx>, rustc_hir::InlineAsmOperand<'_x>;
-            [] asm_template: rustc_ast::ast::InlineAsmTemplatePiece, rustc_ast::ast::InlineAsmTemplatePiece;
-            [] attribute: rustc_ast::ast::Attribute, rustc_ast::ast::Attribute;
-            [] block: rustc_hir::Block<$tcx>, rustc_hir::Block<'_x>;
-            [] bare_fn_ty: rustc_hir::BareFnTy<$tcx>, rustc_hir::BareFnTy<'_x>;
-            [few] global_asm: rustc_hir::GlobalAsm, rustc_hir::GlobalAsm;
-            [] generic_arg: rustc_hir::GenericArg<$tcx>, rustc_hir::GenericArg<'_x>;
-            [] generic_args: rustc_hir::GenericArgs<$tcx>, rustc_hir::GenericArgs<'_x>;
-            [] generic_bound: rustc_hir::GenericBound<$tcx>, rustc_hir::GenericBound<'_x>;
-            [] generic_param: rustc_hir::GenericParam<$tcx>, rustc_hir::GenericParam<'_x>;
-            [] expr: rustc_hir::Expr<$tcx>, rustc_hir::Expr<'_x>;
-            [] field: rustc_hir::Field<$tcx>, rustc_hir::Field<'_x>;
-            [] field_pat: rustc_hir::FieldPat<$tcx>, rustc_hir::FieldPat<'_x>;
-            [] fn_decl: rustc_hir::FnDecl<$tcx>, rustc_hir::FnDecl<'_x>;
-            [] foreign_item: rustc_hir::ForeignItem<$tcx>, rustc_hir::ForeignItem<'_x>;
-            [] impl_item_ref: rustc_hir::ImplItemRef<$tcx>, rustc_hir::ImplItemRef<'_x>;
-            [few] inline_asm: rustc_hir::InlineAsm<$tcx>, rustc_hir::InlineAsm<'_x>;
-            [few] llvm_inline_asm: rustc_hir::LlvmInlineAsm<$tcx>, rustc_hir::LlvmInlineAsm<'_x>;
-            [] local: rustc_hir::Local<$tcx>, rustc_hir::Local<'_x>;
-            [few] macro_def: rustc_hir::MacroDef<$tcx>, rustc_hir::MacroDef<'_x>;
-            [] param: rustc_hir::Param<$tcx>, rustc_hir::Param<'_x>;
-            [] pat: rustc_hir::Pat<$tcx>, rustc_hir::Pat<'_x>;
-            [] path: rustc_hir::Path<$tcx>, rustc_hir::Path<'_x>;
-            [] path_segment: rustc_hir::PathSegment<$tcx>, rustc_hir::PathSegment<'_x>;
-            [] poly_trait_ref: rustc_hir::PolyTraitRef<$tcx>, rustc_hir::PolyTraitRef<'_x>;
-            [] qpath: rustc_hir::QPath<$tcx>, rustc_hir::QPath<'_x>;
-            [] stmt: rustc_hir::Stmt<$tcx>, rustc_hir::Stmt<'_x>;
-            [] struct_field: rustc_hir::StructField<$tcx>, rustc_hir::StructField<'_x>;
-            [] trait_item_ref: rustc_hir::TraitItemRef, rustc_hir::TraitItemRef;
-            [] ty: rustc_hir::Ty<$tcx>, rustc_hir::Ty<'_x>;
-            [] type_binding: rustc_hir::TypeBinding<$tcx>, rustc_hir::TypeBinding<'_x>;
-            [] variant: rustc_hir::Variant<$tcx>, rustc_hir::Variant<'_x>;
-            [] where_predicate: rustc_hir::WherePredicate<$tcx>, rustc_hir::WherePredicate<'_x>;
+            [few] hir_krate: rustc_hir::Crate<$tcx>,
+            [] arm: rustc_hir::Arm<$tcx>,
+            [] asm_operand: rustc_hir::InlineAsmOperand<$tcx>,
+            [] asm_template: rustc_ast::ast::InlineAsmTemplatePiece,
+            [] attribute: rustc_ast::ast::Attribute,
+            [] block: rustc_hir::Block<$tcx>,
+            [] bare_fn_ty: rustc_hir::BareFnTy<$tcx>,
+            [few] global_asm: rustc_hir::GlobalAsm,
+            [] generic_arg: rustc_hir::GenericArg<$tcx>,
+            [] generic_args: rustc_hir::GenericArgs<$tcx>,
+            [] generic_bound: rustc_hir::GenericBound<$tcx>,
+            [] generic_param: rustc_hir::GenericParam<$tcx>,
+            [] expr: rustc_hir::Expr<$tcx>,
+            [] field: rustc_hir::Field<$tcx>,
+            [] field_pat: rustc_hir::FieldPat<$tcx>,
+            [] fn_decl: rustc_hir::FnDecl<$tcx>,
+            [] foreign_item: rustc_hir::ForeignItem<$tcx>,
+            [] impl_item_ref: rustc_hir::ImplItemRef<$tcx>,
+            [few] inline_asm: rustc_hir::InlineAsm<$tcx>,
+            [few] llvm_inline_asm: rustc_hir::LlvmInlineAsm<$tcx>,
+            [] local: rustc_hir::Local<$tcx>,
+            [few] macro_def: rustc_hir::MacroDef<$tcx>,
+            [] param: rustc_hir::Param<$tcx>,
+            [] pat: rustc_hir::Pat<$tcx>,
+            [] path: rustc_hir::Path<$tcx>,
+            [] path_segment: rustc_hir::PathSegment<$tcx>,
+            [] poly_trait_ref: rustc_hir::PolyTraitRef<$tcx>,
+            [] qpath: rustc_hir::QPath<$tcx>,
+            [] stmt: rustc_hir::Stmt<$tcx>,
+            [] struct_field: rustc_hir::StructField<$tcx>,
+            [] trait_item_ref: rustc_hir::TraitItemRef,
+            [] ty: rustc_hir::Ty<$tcx>,
+            [] type_binding: rustc_hir::TypeBinding<$tcx>,
+            [] variant: rustc_hir::Variant<$tcx>,
+            [] where_predicate: rustc_hir::WherePredicate<$tcx>,
         ], $tcx);
     )
 }
diff --git a/src/librustc_middle/arena.rs b/src/librustc_middle/arena.rs
index a08941469ed..99889c74da0 100644
--- a/src/librustc_middle/arena.rs
+++ b/src/librustc_middle/arena.rs
@@ -11,13 +11,11 @@
 macro_rules! arena_types {
     ($macro:path, $args:tt, $tcx:lifetime) => (
         $macro!($args, [
-            [] layouts: rustc_target::abi::Layout, rustc_target::abi::Layout;
+            [] layouts: rustc_target::abi::Layout,
             // AdtDef are interned and compared by address
-            [] adt_def: rustc_middle::ty::AdtDef, rustc_middle::ty::AdtDef;
-            [] steal_mir:
-                rustc_middle::ty::steal::Steal<rustc_middle::mir::Body<$tcx>>,
-                rustc_middle::ty::steal::Steal<rustc_middle::mir::Body<$tcx>>;
-            [decode] mir: rustc_middle::mir::Body<$tcx>, rustc_middle::mir::Body<'_x>;
+            [] adt_def: rustc_middle::ty::AdtDef,
+            [] steal_mir: rustc_middle::ty::steal::Steal<rustc_middle::mir::Body<$tcx>>,
+            [decode] mir: rustc_middle::mir::Body<$tcx>,
             [] steal_promoted:
                 rustc_middle::ty::steal::Steal<
                     rustc_index::vec::IndexVec<
@@ -25,127 +23,86 @@ macro_rules! arena_types {
                         rustc_middle::mir::Body<$tcx>
                     >
                 >,
-                rustc_middle::ty::steal::Steal<
-                    rustc_index::vec::IndexVec<
-                        rustc_middle::mir::Promoted,
-                        rustc_middle::mir::Body<$tcx>
-                    >
-                >;
             [decode] promoted:
                 rustc_index::vec::IndexVec<
                     rustc_middle::mir::Promoted,
                     rustc_middle::mir::Body<$tcx>
                 >,
-                rustc_index::vec::IndexVec<
-                    rustc_middle::mir::Promoted,
-                    rustc_middle::mir::Body<'_x>
-                >;
-            [decode] typeck_results: rustc_middle::ty::TypeckResults<$tcx>, rustc_middle::ty::TypeckResults<'_x>;
+            [decode] typeck_results: rustc_middle::ty::TypeckResults<$tcx>,
             [decode] borrowck_result:
                 rustc_middle::mir::BorrowCheckResult<$tcx>,
-                rustc_middle::mir::BorrowCheckResult<'_x>;
-            [decode] unsafety_check_result: rustc_middle::mir::UnsafetyCheckResult, rustc_middle::mir::UnsafetyCheckResult;
-            [] const_allocs: rustc_middle::mir::interpret::Allocation, rustc_middle::mir::interpret::Allocation;
+            [decode] unsafety_check_result: rustc_middle::mir::UnsafetyCheckResult,
+            [] const_allocs: rustc_middle::mir::interpret::Allocation,
             // Required for the incremental on-disk cache
-            [few] mir_keys: rustc_hir::def_id::DefIdSet, rustc_hir::def_id::DefIdSet;
-            [] region_scope_tree: rustc_middle::middle::region::ScopeTree, rustc_middle::middle::region::ScopeTree;
+            [few] mir_keys: rustc_hir::def_id::DefIdSet,
+            [] region_scope_tree: rustc_middle::middle::region::ScopeTree,
             [] dropck_outlives:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx,
                         rustc_middle::traits::query::DropckOutlivesResult<'tcx>
                     >
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y,
-                        rustc_middle::traits::query::DropckOutlivesResult<'_z>
-                    >
-                >;
             [] normalize_projection_ty:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx,
                         rustc_middle::traits::query::NormalizationResult<'tcx>
                     >
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y,
-                        rustc_middle::traits::query::NormalizationResult<'_z>
-                    >
-                >;
             [] implied_outlives_bounds:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx,
                         Vec<rustc_middle::traits::query::OutlivesBound<'tcx>>
                     >
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y,
-                        Vec<rustc_middle::traits::query::OutlivesBound<'_z>>
-                    >
-                >;
             [] type_op_subtype:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx, ()>
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y, ()>
-                >;
             [] type_op_normalize_poly_fn_sig:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::PolyFnSig<'tcx>>
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y, rustc_middle::ty::PolyFnSig<'_z>>
-                >;
             [] type_op_normalize_fn_sig:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::FnSig<'tcx>>
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y, rustc_middle::ty::FnSig<'_z>>
-                >;
             [] type_op_normalize_predicate:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::Predicate<'tcx>>
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y, rustc_middle::ty::Predicate<'_z>>
-                >;
             [] type_op_normalize_ty:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::Ty<'tcx>>
                 >,
-                rustc_middle::infer::canonical::Canonical<'_x,
-                    rustc_middle::infer::canonical::QueryResponse<'_y, &'_z rustc_middle::ty::TyS<'_w>>
-                >;
-            [few] all_traits: Vec<rustc_hir::def_id::DefId>, Vec<rustc_hir::def_id::DefId>;
-            [few] privacy_access_levels: rustc_middle::middle::privacy::AccessLevels, rustc_middle::middle::privacy::AccessLevels;
-            [few] foreign_module: rustc_middle::middle::cstore::ForeignModule, rustc_middle::middle::cstore::ForeignModule;
-            [few] foreign_modules: Vec<rustc_middle::middle::cstore::ForeignModule>, Vec<rustc_middle::middle::cstore::ForeignModule>;
-            [] upvars_mentioned: rustc_data_structures::fx::FxIndexMap<rustc_hir::HirId, rustc_hir::Upvar>, rustc_data_structures::fx::FxIndexMap<rustc_hir::HirId, rustc_hir::Upvar>;
-            [] object_safety_violations: rustc_middle::traits::ObjectSafetyViolation, rustc_middle::traits::ObjectSafetyViolation;
-            [] codegen_unit: rustc_middle::mir::mono::CodegenUnit<$tcx>, rustc_middle::mir::mono::CodegenUnit<'_x>;
-            [] attribute: rustc_ast::ast::Attribute, rustc_ast::ast::Attribute;
-            [] name_set: rustc_data_structures::fx::FxHashSet<rustc_span::symbol::Symbol>, rustc_data_structures::fx::FxHashSet<rustc_span::symbol::Symbol>;
-            [] hir_id_set: rustc_hir::HirIdSet, rustc_hir::HirIdSet;
+            [few] all_traits: Vec<rustc_hir::def_id::DefId>,
+            [few] privacy_access_levels: rustc_middle::middle::privacy::AccessLevels,
+            [few] foreign_module: rustc_middle::middle::cstore::ForeignModule,
+            [few] foreign_modules: Vec<rustc_middle::middle::cstore::ForeignModule>,
+            [] upvars_mentioned: rustc_data_structures::fx::FxIndexMap<rustc_hir::HirId, rustc_hir::Upvar>,
+            [] object_safety_violations: rustc_middle::traits::ObjectSafetyViolation,
+            [] codegen_unit: rustc_middle::mir::mono::CodegenUnit<$tcx>,
+            [] attribute: rustc_ast::ast::Attribute,
+            [] name_set: rustc_data_structures::fx::FxHashSet<rustc_span::symbol::Symbol>,
+            [] hir_id_set: rustc_hir::HirIdSet,
 
             // Interned types
-            [] tys: rustc_middle::ty::TyS<$tcx>, rustc_middle::ty::TyS<'_x>;
-            [] predicates: rustc_middle::ty::PredicateInner<$tcx>, rustc_middle::ty::PredicateInner<'_x>;
+            [] tys: rustc_middle::ty::TyS<$tcx>,
+            [] predicates: rustc_middle::ty::PredicateInner<$tcx>,
 
             // HIR query types
-            [few] indexed_hir: rustc_middle::hir::map::IndexedHir<$tcx>, rustc_middle::hir::map::IndexedHir<'_x>;
-            [few] hir_definitions: rustc_hir::definitions::Definitions, rustc_hir::definitions::Definitions;
-            [] hir_owner: rustc_middle::hir::Owner<$tcx>, rustc_middle::hir::Owner<'_x>;
-            [] hir_owner_nodes: rustc_middle::hir::OwnerNodes<$tcx>, rustc_middle::hir::OwnerNodes<'_x>;
+            [few] indexed_hir: rustc_middle::hir::map::IndexedHir<$tcx>,
+            [few] hir_definitions: rustc_hir::definitions::Definitions,
+            [] hir_owner: rustc_middle::hir::Owner<$tcx>,
+            [] hir_owner_nodes: rustc_middle::hir::OwnerNodes<$tcx>,
 
             // Note that this deliberately duplicates items in the `rustc_hir::arena`,
             // since we need to allocate this type on both the `rustc_hir` arena
             // (during lowering) and the `librustc_middle` arena (for decoding MIR)
-            [decode] asm_template: rustc_ast::ast::InlineAsmTemplatePiece, rustc_ast::ast::InlineAsmTemplatePiece;
+            [decode] asm_template: rustc_ast::ast::InlineAsmTemplatePiece,
 
             // This is used to decode the &'tcx [Span] for InlineAsm's line_spans.
-            [decode] span: rustc_span::Span, rustc_span::Span;
-            [decode] used_trait_imports: rustc_data_structures::fx::FxHashSet<rustc_hir::def_id::LocalDefId>, rustc_data_structures::fx::FxHashSet<rustc_hir::def_id::LocalDefId>;
+            [decode] span: rustc_span::Span,
+            [decode] used_trait_imports: rustc_data_structures::fx::FxHashSet<rustc_hir::def_id::LocalDefId>,
         ], $tcx);
     )
 }
diff --git a/src/librustc_middle/ty/codec.rs b/src/librustc_middle/ty/codec.rs
index 42f55e9f5f9..270eb42b0c7 100644
--- a/src/librustc_middle/ty/codec.rs
+++ b/src/librustc_middle/ty/codec.rs
@@ -390,7 +390,7 @@ macro_rules! impl_arena_allocatable_decoder {
 }
 
 macro_rules! impl_arena_allocatable_decoders {
-    ([], [$($a:tt $name:ident: $ty:ty, $_gen_ty:ty;)*], $tcx:lifetime) => {
+    ([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
         $(
             impl_arena_allocatable_decoder!($a [[$name: $ty], $tcx]);
         )*