Add an indirection for closures in hir::ExprKind

This helps bring `hir::Expr` size down, `Closure` was the biggest
variant, especially after `for<>` additions.

Author: WaffleLapkin

compiler/rustc_ast_lowering/src/expr.rs

@@ -608,14 +608,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
         });
 
         // `static |_task_context| -> <ret_ty> { body }`:
-        let generator_kind = hir::ExprKind::Closure {
-            binder: &hir::ClosureBinder::Default,
-            capture_clause,
-            bound_generic_params: &[],
-            fn_decl,
-            body,
-            fn_decl_span: self.lower_span(span),
-            movability: Some(hir::Movability::Static),
+        let generator_kind = {
+            let c = self.arena.alloc(hir::Closure {
+                binder: hir::ClosureBinder::Default,
+                capture_clause,
+                bound_generic_params: &[],
+                fn_decl,
+                body,
+                fn_decl_span: self.lower_span(span),
+                movability: Some(hir::Movability::Static),
+            });
+
+            hir::ExprKind::Closure(c)
         };
         let generator = hir::Expr {
             hir_id: self.lower_node_id(closure_node_id),
@@ -864,15 +868,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
             // Lower outside new scope to preserve `is_in_loop_condition`.
             let fn_decl = this.lower_fn_decl(decl, None, FnDeclKind::Closure, None);
 
-            hir::ExprKind::Closure {
+            let c = self.arena.alloc(hir::Closure {
                 binder: binder_clause,
                 capture_clause,
                 bound_generic_params,
                 fn_decl,
                 body: body_id,
                 fn_decl_span: this.lower_span(fn_decl_span),
                 movability: generator_option,
-            }
+            });
+
+            hir::ExprKind::Closure(c)
         })
     }
 
@@ -917,7 +923,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_closure_binder<'c>(
         &mut self,
         binder: &'c ClosureBinder,
-    ) -> (&'hir hir::ClosureBinder, &'c [GenericParam]) {
+    ) -> (hir::ClosureBinder, &'c [GenericParam]) {
         let (binder, params) = match binder {
             ClosureBinder::NotPresent => (hir::ClosureBinder::Default, &[][..]),
             &ClosureBinder::For { span, ref generic_params } => {
@@ -926,7 +932,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
         };
 
-        (self.arena.alloc(binder), params)
+        (binder, params)
     }
 
     fn lower_expr_async_closure(
@@ -991,15 +997,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
             // closure argument types.
             let fn_decl = this.lower_fn_decl(&outer_decl, None, FnDeclKind::Closure, None);
 
-            hir::ExprKind::Closure {
+            let c = self.arena.alloc(hir::Closure {
                 binder: binder_clause,
                 capture_clause,
                 bound_generic_params,
                 fn_decl,
                 body,
                 fn_decl_span: this.lower_span(fn_decl_span),
                 movability: None,
-            }
+            });
+            hir::ExprKind::Closure(c)
         })
     }
 

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -891,7 +891,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let hir_id = self.infcx.tcx.hir().local_def_id_to_hir_id(local_did);
         let expr = &self.infcx.tcx.hir().expect_expr(hir_id).kind;
         debug!("closure_span: hir_id={:?} expr={:?}", hir_id, expr);
-        if let hir::ExprKind::Closure { body, fn_decl_span, .. } = expr {
+        if let hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }) = expr {
             for (captured_place, place) in self
                 .infcx
                 .tcx
@@ -904,11 +904,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         if target_place == place.as_ref() =>
                     {
                         debug!("closure_span: found captured local {:?}", place);
-                        let body = self.infcx.tcx.hir().body(*body);
+                        let body = self.infcx.tcx.hir().body(body);
                         let generator_kind = body.generator_kind();
 
                         return Some((
-                            *fn_decl_span,
+                            fn_decl_span,
                             generator_kind,
                             captured_place.get_capture_kind_span(self.infcx.tcx),
                             captured_place.get_path_span(self.infcx.tcx),

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -325,7 +325,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                         // Can't have BrEnv in functions, constants or generators.
                         bug!("BrEnv outside of closure.");
                     };
-                    let hir::ExprKind::Closure { fn_decl_span, .. }
+                    let hir::ExprKind::Closure(&hir::Closure { fn_decl_span, .. })
                         = tcx.hir().expect_expr(self.mir_hir_id()).kind
                     else {
                         bug!("Closure is not defined by a closure expr");
@@ -701,16 +701,16 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         let (return_span, mir_description, hir_ty) = match hir.get(mir_hir_id) {
             hir::Node::Expr(hir::Expr {
-                kind: hir::ExprKind::Closure { fn_decl, body, fn_decl_span, .. },
+                kind: hir::ExprKind::Closure(&hir::Closure { fn_decl, body, fn_decl_span, .. }),
                 ..
             }) => {
                 let (mut span, mut hir_ty) = match fn_decl.output {
                     hir::FnRetTy::DefaultReturn(_) => {
-                        (tcx.sess.source_map().end_point(*fn_decl_span), None)
+                        (tcx.sess.source_map().end_point(fn_decl_span), None)
                     }
                     hir::FnRetTy::Return(hir_ty) => (fn_decl.output.span(), Some(hir_ty)),
                 };
-                let mir_description = match hir.body(*body).generator_kind {
+                let mir_description = match hir.body(body).generator_kind {
                     Some(hir::GeneratorKind::Async(gen)) => match gen {
                         hir::AsyncGeneratorKind::Block => " of async block",
                         hir::AsyncGeneratorKind::Closure => " of async closure",
@@ -841,9 +841,9 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         let yield_span = match tcx.hir().get(self.mir_hir_id()) {
             hir::Node::Expr(hir::Expr {
-                kind: hir::ExprKind::Closure { fn_decl_span, .. },
+                kind: hir::ExprKind::Closure(&hir::Closure { fn_decl_span, .. }),
                 ..
-            }) => (tcx.sess.source_map().end_point(*fn_decl_span)),
+            }) => (tcx.sess.source_map().end_point(fn_decl_span)),
             _ => self.body.span,
         };
 

compiler/rustc_hir/src/arena.rs

@@ -12,6 +12,7 @@ macro_rules! arena_types {
             [] 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>,

compiler/rustc_hir/src/hir.rs

@@ -922,6 +922,17 @@ pub struct Crate<'hir> {
     pub hir_hash: Fingerprint,
 }
 
+#[derive(Debug, HashStable_Generic)]
+pub struct Closure<'hir> {
+    pub binder: ClosureBinder,
+    pub capture_clause: CaptureBy,
+    pub bound_generic_params: &'hir [GenericParam<'hir>],
+    pub fn_decl: &'hir FnDecl<'hir>,
+    pub body: BodyId,
+    pub fn_decl_span: Span,
+    pub movability: Option<Movability>,
+}
+
 /// A block of statements `{ .. }`, which may have a label (in this case the
 /// `targeted_by_break` field will be `true`) and may be `unsafe` by means of
 /// the `rules` being anything but `DefaultBlock`.
@@ -1930,15 +1941,7 @@ pub enum ExprKind<'hir> {
     ///
     /// This may also be a generator literal or an `async block` as indicated by the
     /// `Option<Movability>`.
-    Closure {
-        binder: &'hir ClosureBinder,
-        capture_clause: CaptureBy,
-        bound_generic_params: &'hir [GenericParam<'hir>],
-        fn_decl: &'hir FnDecl<'hir>,
-        body: BodyId,
-        fn_decl_span: Span,
-        movability: Option<Movability>,
-    },
+    Closure(&'hir Closure<'hir>),
     /// A block (e.g., `'label: { ... }`).
     Block(&'hir Block<'hir>, Option<Label>),
 

compiler/rustc_hir/src/intravisit.rs

@@ -1144,23 +1144,17 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>)
             visitor.visit_expr(subexpression);
             walk_list!(visitor, visit_arm, arms);
         }
-        ExprKind::Closure {
+        ExprKind::Closure(&Closure {
             binder: _,
             bound_generic_params,
-            ref fn_decl,
+            fn_decl,
             body,
             capture_clause: _,
             fn_decl_span: _,
             movability: _,
-        } => {
+        }) => {
             walk_list!(visitor, visit_generic_param, bound_generic_params);
-            visitor.visit_fn(
-                FnKind::Closure,
-                fn_decl,
-                body,
-                expression.span,
-                expression.hir_id,
-            )
+            visitor.visit_fn(FnKind::Closure, fn_decl, body, expression.span, expression.hir_id)
         }
         ExprKind::Block(ref block, ref opt_label) => {
             walk_list!(visitor, visit_label, opt_label);

compiler/rustc_hir_pretty/src/lib.rs

@@ -1441,15 +1441,15 @@ impl<'a> State<'a> {
                 }
                 self.bclose(expr.span);
             }
-            hir::ExprKind::Closure {
+            hir::ExprKind::Closure(&hir::Closure {
                 binder,
                 capture_clause,
                 bound_generic_params,
                 fn_decl,
                 body,
                 fn_decl_span: _,
                 movability: _,
-            } => {
+            }) => {
                 self.print_closure_binder(binder, bound_generic_params);
                 self.print_capture_clause(capture_clause);
 
@@ -2037,7 +2037,7 @@ impl<'a> State<'a> {
 
     pub fn print_closure_binder(
         &mut self,
-        binder: &hir::ClosureBinder,
+        binder: hir::ClosureBinder,
         generic_params: &[GenericParam<'_>],
     ) {
         let generic_params = generic_params

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -6,7 +6,7 @@ use rustc_hir::def::Res;
 use rustc_hir::def::{CtorOf, DefKind, Namespace};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{Body, Expr, ExprKind, FnRetTy, HirId, Local, LocalSource};
+use rustc_hir::{Body, Closure, Expr, ExprKind, FnRetTy, HirId, Local, LocalSource};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::infer::unify_key::ConstVariableOriginKind;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
@@ -1051,7 +1051,7 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
 
         if let Some(node_ty) = self.opt_node_type(expr.hir_id) {
             if let (
-                &ExprKind::Closure { fn_decl, body, fn_decl_span, .. },
+                &ExprKind::Closure(&Closure { fn_decl, body, fn_decl_span, .. }),
                 ty::Closure(_, substs),
             ) = (&expr.kind, node_ty.kind())
             {

compiler/rustc_middle/src/hir/map/mod.rs

@@ -22,7 +22,7 @@ fn fn_decl<'hir>(node: Node<'hir>) -> Option<&'hir FnDecl<'hir>> {
         Node::Item(Item { kind: ItemKind::Fn(sig, _, _), .. })
         | Node::TraitItem(TraitItem { kind: TraitItemKind::Fn(sig, _), .. })
         | Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(sig, _), .. }) => Some(&sig.decl),
-        Node::Expr(Expr { kind: ExprKind::Closure { fn_decl, .. }, .. })
+        Node::Expr(Expr { kind: ExprKind::Closure(Closure { fn_decl, .. }), .. })
         | Node::ForeignItem(ForeignItem { kind: ForeignItemKind::Fn(fn_decl, ..), .. }) => {
             Some(fn_decl)
         }
@@ -54,7 +54,7 @@ pub fn associated_body<'hir>(node: Node<'hir>) -> Option<BodyId> {
             kind: ImplItemKind::Const(_, body) | ImplItemKind::Fn(_, body),
             ..
         })
-        | Node::Expr(Expr { kind: ExprKind::Closure { body, .. }, .. }) => Some(*body),
+        | Node::Expr(Expr { kind: ExprKind::Closure(Closure { body, .. }), .. }) => Some(*body),
 
         Node::AnonConst(constant) => Some(constant.body),
 
@@ -279,8 +279,8 @@ impl<'hir> Map<'hir> {
             }
             Node::Field(_) => DefKind::Field,
             Node::Expr(expr) => match expr.kind {
-                ExprKind::Closure { movability: None, .. } => DefKind::Closure,
-                ExprKind::Closure { movability: Some(_), .. } => DefKind::Generator,
+                ExprKind::Closure(Closure { movability: None, .. }) => DefKind::Closure,
+                ExprKind::Closure(Closure { movability: Some(_), .. }) => DefKind::Generator,
                 _ => bug!("def_kind: unsupported node: {}", self.node_to_string(hir_id)),
             },
             Node::GenericParam(param) => match param.kind {
@@ -1021,7 +1021,9 @@ impl<'hir> Map<'hir> {
                 _ => named_span(item.span, item.ident, None),
             },
             Node::Ctor(_) => return self.opt_span(self.get_parent_node(hir_id)),
-            Node::Expr(Expr { kind: ExprKind::Closure { fn_decl_span, .. }, .. }) => *fn_decl_span,
+            Node::Expr(Expr { kind: ExprKind::Closure(Closure { fn_decl_span, .. }), .. }) => {
+                *fn_decl_span
+            }
             _ => self.span_with_body(hir_id),
         };
         Some(span)

compiler/rustc_mir_build/src/build/mod.rs

@@ -68,9 +68,10 @@ fn mir_build(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_
 
     // Figure out what primary body this item has.
     let (body_id, return_ty_span, span_with_body) = match tcx.hir().get(id) {
-        Node::Expr(hir::Expr { kind: hir::ExprKind::Closure { fn_decl, body, .. }, .. }) => {
-            (*body, fn_decl.output.span(), None)
-        }
+        Node::Expr(hir::Expr {
+            kind: hir::ExprKind::Closure(hir::Closure { fn_decl, body, .. }),
+            ..
+        }) => (*body, fn_decl.output.span(), None),
         Node::Item(hir::Item {
             kind: hir::ItemKind::Fn(hir::FnSig { decl, .. }, _, body_id),
             span,