ast: Reduce size of ExprKind by boxing fields of ExprKind::Struct

Author: petrochenkov

compiler/rustc_ast/src/ast.rs

@@ -1074,7 +1074,7 @@ pub struct Expr {
 
 // `Expr` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-rustc_data_structures::static_assert_size!(Expr, 120);
+rustc_data_structures::static_assert_size!(Expr, 104);
 
 impl Expr {
     /// Returns `true` if this expression would be valid somewhere that expects a value;
@@ -1244,6 +1244,13 @@ pub enum StructRest {
     None,
 }
 
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct StructExpr {
+    pub path: Path,
+    pub fields: Vec<ExprField>,
+    pub rest: StructRest,
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum ExprKind {
     /// A `box x` expression.
@@ -1369,7 +1376,7 @@ pub enum ExprKind {
     /// A struct literal expression.
     ///
     /// E.g., `Foo {x: 1, y: 2}`, or `Foo {x: 1, .. rest}`.
-    Struct(Path, Vec<ExprField>, StructRest),
+    Struct(P<StructExpr>),
 
     /// An array literal constructed from one repeated element.
     ///

compiler/rustc_ast/src/mut_visit.rs

@@ -1286,10 +1286,11 @@ pub fn noop_visit_expr<T: MutVisitor>(
             visit_vec(inputs, |(_c, expr)| vis.visit_expr(expr));
         }
         ExprKind::MacCall(mac) => vis.visit_mac_call(mac),
-        ExprKind::Struct(path, fields, expr) => {
+        ExprKind::Struct(se) => {
+            let StructExpr { path, fields, rest } = se.deref_mut();
             vis.visit_path(path);
             fields.flat_map_in_place(|field| vis.flat_map_expr_field(field));
-            match expr {
+            match rest {
                 StructRest::Base(expr) => vis.visit_expr(expr),
                 StructRest::Rest(_span) => {}
                 StructRest::None => {}

compiler/rustc_ast/src/visit.rs

@@ -721,10 +721,10 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             visitor.visit_expr(element);
             visitor.visit_anon_const(count)
         }
-        ExprKind::Struct(ref path, ref fields, ref optional_base) => {
-            visitor.visit_path(path, expression.id);
-            walk_list!(visitor, visit_expr_field, fields);
-            match optional_base {
+        ExprKind::Struct(ref se) => {
+            visitor.visit_path(&se.path, expression.id);
+            walk_list!(visitor, visit_expr_field, &se.fields);
+            match &se.rest {
                 StructRest::Base(expr) => visitor.visit_expr(expr),
                 StructRest::Rest(_span) => {}
                 StructRest::None => {}

compiler/rustc_ast_lowering/src/expr.rs

@@ -224,8 +224,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
                 ExprKind::InlineAsm(ref asm) => self.lower_expr_asm(e.span, asm),
                 ExprKind::LlvmInlineAsm(ref asm) => self.lower_expr_llvm_asm(asm),
-                ExprKind::Struct(ref path, ref fields, ref rest) => {
-                    let rest = match rest {
+                ExprKind::Struct(ref se) => {
+                    let rest = match &se.rest {
                         StructRest::Base(e) => Some(self.lower_expr(e)),
                         StructRest::Rest(sp) => {
                             self.sess
@@ -240,11 +240,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         self.arena.alloc(self.lower_qpath(
                             e.id,
                             &None,
-                            path,
+                            &se.path,
                             ParamMode::Optional,
                             ImplTraitContext::disallowed(),
                         )),
-                        self.arena.alloc_from_iter(fields.iter().map(|x| self.lower_expr_field(x))),
+                        self.arena
+                            .alloc_from_iter(se.fields.iter().map(|x| self.lower_expr_field(x))),
                         rest,
                     )
                 }
@@ -1110,8 +1111,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
             }
             // Structs.
-            ExprKind::Struct(path, fields, rest) => {
-                let field_pats = self.arena.alloc_from_iter(fields.iter().map(|f| {
+            ExprKind::Struct(se) => {
+                let field_pats = self.arena.alloc_from_iter(se.fields.iter().map(|f| {
                     let pat = self.destructure_assign(&f.expr, eq_sign_span, assignments);
                     hir::PatField {
                         hir_id: self.next_id(),
@@ -1124,11 +1125,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let qpath = self.lower_qpath(
                     lhs.id,
                     &None,
-                    path,
+                    &se.path,
                     ParamMode::Optional,
                     ImplTraitContext::disallowed(),
                 );
-                let fields_omitted = match rest {
+                let fields_omitted = match &se.rest {
                     StructRest::Base(e) => {
                         self.sess
                             .struct_span_err(

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1873,8 +1873,8 @@ impl<'a> State<'a> {
             ast::ExprKind::Repeat(ref element, ref count) => {
                 self.print_expr_repeat(element, count, attrs);
             }
-            ast::ExprKind::Struct(ref path, ref fields, ref rest) => {
-                self.print_expr_struct(path, &fields[..], rest, attrs);
+            ast::ExprKind::Struct(ref se) => {
+                self.print_expr_struct(&se.path, &se.fields, &se.rest, attrs);
             }
             ast::ExprKind::Tup(ref exprs) => {
                 self.print_expr_tup(&exprs[..], attrs);

compiler/rustc_expand/src/build.rs

@@ -284,7 +284,10 @@ impl<'a> ExtCtxt<'a> {
         path: ast::Path,
         fields: Vec<ast::ExprField>,
     ) -> P<ast::Expr> {
-        self.expr(span, ast::ExprKind::Struct(path, fields, ast::StructRest::None))
+        self.expr(
+            span,
+            ast::ExprKind::Struct(P(ast::StructExpr { path, fields, rest: ast::StructRest::None })),
+        )
     }
     pub fn expr_struct_ident(
         &self,

compiler/rustc_parse/src/parser/expr.rs

@@ -2373,7 +2373,11 @@ impl<'a> Parser<'a> {
 
         let span = pth.span.to(self.token.span);
         self.expect(&token::CloseDelim(token::Brace))?;
-        let expr = if recover_async { ExprKind::Err } else { ExprKind::Struct(pth, fields, base) };
+        let expr = if recover_async {
+            ExprKind::Err
+        } else {
+            ExprKind::Struct(P(ast::StructExpr { path: pth, fields, rest: base }))
+        };
         Ok(self.mk_expr(span, expr, attrs))
     }
 

compiler/rustc_resolve/src/late.rs

@@ -2251,8 +2251,8 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 visit::walk_expr(self, expr);
             }
 
-            ExprKind::Struct(ref path, ..) => {
-                self.smart_resolve_path(expr.id, None, path, PathSource::Struct);
+            ExprKind::Struct(ref se) => {
+                self.smart_resolve_path(expr.id, None, &se.path, PathSource::Struct);
                 visit::walk_expr(self, expr);
             }
 

src/test/ui-fulldeps/pprust-expr-roundtrip.rs

@@ -155,7 +155,9 @@ fn iter_exprs(depth: usize, f: &mut dyn FnMut(P<Expr>)) {
             },
             17 => {
                 let path = Path::from_ident(Ident::from_str("S"));
-                g(ExprKind::Struct(path, vec![], StructRest::Base(make_x())));
+                g(ExprKind::Struct(P(StructExpr {
+                    path, fields: vec![], rest: StructRest::Base(make_x())
+                })));
             },
             18 => {
                 iter_exprs(depth - 1, &mut |e| g(ExprKind::Try(e)));

src/tools/clippy/clippy_lints/src/redundant_field_names.rs

@@ -58,8 +58,8 @@ impl EarlyLintPass for RedundantFieldNames {
         if in_external_macro(cx.sess, expr.span) {
             return;
         }
-        if let ExprKind::Struct(_, ref fields, _) = expr.kind {
-            for field in fields {
+        if let ExprKind::Struct(ref se) = expr.kind {
+            for field in &se.fields {
                 if field.is_shorthand {
                     continue;
                 }