Impl Copy for almost all HIR types

This simplifies the invocation of the `arena_types` macro and probably
makes working with HIR nicer in general.

Author: Noratrieb

compiler/rustc_hir/src/arena.rs

@@ -1,56 +1,16 @@
 /// This higher-order macro declares a list of types which can be allocated by `Arena`.
-///
-/// Specifying the `decode` modifier will add decode impls for `&T` and `&[T]`,
-/// where `T` is the type listed. These impls will appear in the implement_ty_decoder! macro.
+/// Note that all `Copy` types can be allocated by default and need not be specified here.
 #[macro_export]
 macro_rules! arena_types {
     ($macro:path) => (
         $macro!([
             // HIR types
             [] hir_krate: rustc_hir::Crate<'tcx>,
-            [] arm: rustc_hir::Arm<'tcx>,
-            [] asm_operand: (rustc_hir::InlineAsmOperand<'tcx>, rustc_span::Span),
             [] asm_template: rustc_ast::InlineAsmTemplatePiece,
             [] attribute: rustc_ast::Attribute,
-            [] closure: rustc_hir::Closure<'tcx>,
-            [] block: rustc_hir::Block<'tcx>,
-            [] bare_fn_ty: rustc_hir::BareFnTy<'tcx>,
-            [] body: rustc_hir::Body<'tcx>,
-            [] generics: rustc_hir::Generics<'tcx>,
-            [] 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>,
-            [] impl_: rustc_hir::Impl<'tcx>,
-            [] let_expr: rustc_hir::Let<'tcx>,
-            [] expr_field: rustc_hir::ExprField<'tcx>,
-            [] pat_field: rustc_hir::PatField<'tcx>,
-            [] fn_decl: rustc_hir::FnDecl<'tcx>,
-            [] foreign_item: rustc_hir::ForeignItem<'tcx>,
-            [] foreign_item_ref: rustc_hir::ForeignItemRef,
-            [] impl_item: rustc_hir::ImplItem<'tcx>,
-            [] impl_item_ref: rustc_hir::ImplItemRef,
             [] item: rustc_hir::Item<'tcx>,
-            [] inline_asm: rustc_hir::InlineAsm<'tcx>,
-            [] local: rustc_hir::Local<'tcx>,
-            [] mod_: rustc_hir::Mod<'tcx>,
             [] owner_info: rustc_hir::OwnerInfo<'tcx>,
-            [] param: rustc_hir::Param<'tcx>,
-            [] pat: rustc_hir::Pat<'tcx>,
-            [] path: rustc_hir::Path<'tcx>,
             [] use_path: rustc_hir::UsePath<'tcx>,
-            [] path_segment: rustc_hir::PathSegment<'tcx>,
-            [] poly_trait_ref: rustc_hir::PolyTraitRef<'tcx>,
-            [] qpath: rustc_hir::QPath<'tcx>,
-            [] stmt: rustc_hir::Stmt<'tcx>,
-            [] field_def: rustc_hir::FieldDef<'tcx>,
-            [] trait_item: rustc_hir::TraitItem<'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>,
             [] lit: rustc_hir::Lit,
         ]);
     )