Use &'hir Expr everywhere.

For consistency, and because it makes HIR measurement simpler and more
accurate.

compiler/rustc_ast_lowering/src/asm.rs

@@ -155,26 +155,26 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 let op = match *op {
                     InlineAsmOperand::In { reg, ref expr } => hir::InlineAsmOperand::In {
                         reg: lower_reg(reg),
-                        expr: self.lower_expr_mut(expr),
+                        expr: self.lower_expr(expr),
                     },
                     InlineAsmOperand::Out { reg, late, ref expr } => hir::InlineAsmOperand::Out {
                         reg: lower_reg(reg),
                         late,
-                        expr: expr.as_ref().map(|expr| self.lower_expr_mut(expr)),
+                        expr: expr.as_ref().map(|expr| self.lower_expr(expr)),
                     },
                     InlineAsmOperand::InOut { reg, late, ref expr } => {
                         hir::InlineAsmOperand::InOut {
                             reg: lower_reg(reg),
                             late,
-                            expr: self.lower_expr_mut(expr),
+                            expr: self.lower_expr(expr),
                         }
                     }
                     InlineAsmOperand::SplitInOut { reg, late, ref in_expr, ref out_expr } => {
                         hir::InlineAsmOperand::SplitInOut {
                             reg: lower_reg(reg),
                             late,
-                            in_expr: self.lower_expr_mut(in_expr),
+                            in_expr: self.lower_expr(in_expr),
-                            out_expr: out_expr.as_ref().map(|expr| self.lower_expr_mut(expr)),
+                            out_expr: out_expr.as_ref().map(|expr| self.lower_expr(expr)),
                         }
                     }
                     InlineAsmOperand::Const { ref anon_const } => {

compiler/rustc_ast_lowering/src/item.rs

@@ -947,7 +947,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
         params: &'hir [hir::Param<'hir>],
         value: hir::Expr<'hir>,
     ) -> hir::BodyId {
-        let body = hir::Body { generator_kind: self.generator_kind, params, value };
+        let body = hir::Body {
+            generator_kind: self.generator_kind,
+            params,
+            value: self.arena.alloc(value),
+        };
         let id = body.id();
         debug_assert_eq!(id.hir_id.owner, self.current_hir_id_owner);
         self.bodies.push((id.hir_id.local_id, self.arena.alloc(body)));

compiler/rustc_hir/src/hir.rs

@@ -1438,7 +1438,7 @@ pub struct BodyId {
 #[derive(Debug, HashStable_Generic)]
 pub struct Body<'hir> {
     pub params: &'hir [Param<'hir>],
-    pub value: Expr<'hir>,
+    pub value: &'hir Expr<'hir>,
     pub generator_kind: Option<GeneratorKind>,
 }
 
@@ -2561,23 +2561,23 @@ pub enum TyKind<'hir> {
 pub enum InlineAsmOperand<'hir> {
     In {
         reg: InlineAsmRegOrRegClass,
-        expr: Expr<'hir>,
+        expr: &'hir Expr<'hir>,
     },
     Out {
         reg: InlineAsmRegOrRegClass,
         late: bool,
-        expr: Option<Expr<'hir>>,
+        expr: Option<&'hir Expr<'hir>>,
     },
     InOut {
         reg: InlineAsmRegOrRegClass,
         late: bool,
-        expr: Expr<'hir>,
+        expr: &'hir Expr<'hir>,
     },
     SplitInOut {
         reg: InlineAsmRegOrRegClass,
         late: bool,
-        in_expr: Expr<'hir>,
+        in_expr: &'hir Expr<'hir>,
-        out_expr: Option<Expr<'hir>>,
+        out_expr: Option<&'hir Expr<'hir>>,
     },
     Const {
         anon_const: AnonConst,
@@ -3496,7 +3496,7 @@ mod size_asserts {
     use super::*;
     // These are in alphabetical order, which is easy to maintain.
     static_assert_size!(Block<'_>, 48);
-    static_assert_size!(Body<'_>, 80);
+    static_assert_size!(Body<'_>, 32);
     static_assert_size!(Expr<'_>, 56);
     static_assert_size!(ExprKind<'_>, 40);
     static_assert_size!(FnDecl<'_>, 40);

compiler/rustc_save_analysis/src/dump_visitor.rs

@@ -974,7 +974,7 @@ impl<'tcx> DumpVisitor<'tcx> {
         self.process_macro_use(trait_item.span);
         match trait_item.kind {
             hir::TraitItemKind::Const(ref ty, body) => {
-                let body = body.map(|b| &self.tcx.hir().body(b).value);
+                let body = body.map(|b| self.tcx.hir().body(b).value);
                 let attrs = self.tcx.hir().attrs(trait_item.hir_id());
                 self.process_assoc_const(
                     trait_item.def_id,

src/tools/clippy/clippy_lints/src/loops/never_loop.rs

@@ -178,9 +178,9 @@ fn never_loop_expr(expr: &Expr<'_>, main_loop_id: HirId) -> NeverLoopResult {
                 InlineAsmOperand::In { expr, .. } | InlineAsmOperand::InOut { expr, .. } => {
                     never_loop_expr(expr, main_loop_id)
                 },
-                InlineAsmOperand::Out { expr, .. } => never_loop_expr_all(&mut expr.iter(), main_loop_id),
+                InlineAsmOperand::Out { expr, .. } => never_loop_expr_all(&mut expr.iter().copied(), main_loop_id),
                 InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
-                    never_loop_expr_all(&mut once(in_expr).chain(out_expr.iter()), main_loop_id)
+                    never_loop_expr_all(&mut once(*in_expr).chain(out_expr.iter().copied()), main_loop_id)
                 },
                 InlineAsmOperand::Const { .. }
                 | InlineAsmOperand::SymFn { .. }

src/tools/clippy/clippy_lints/src/utils/author.rs

@@ -595,7 +595,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
     }
 
     fn body(&self, body_id: &Binding<hir::BodyId>) {
-        let expr = &self.cx.tcx.hir().body(body_id.value).value;
+        let expr = self.cx.tcx.hir().body(body_id.value).value;
         bind!(self, expr);
         out!("let {expr} = &cx.tcx.hir().body({body_id}).value;");
         self.expr(expr);

src/tools/clippy/clippy_utils/src/lib.rs

@@ -1804,7 +1804,7 @@ pub fn is_expr_identity_function(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool
             }
         };
 
-        let mut expr = &func.value;
+        let mut expr = func.value;
         loop {
             match expr.kind {
                 #[rustfmt::skip]