Bug 1841330 - Use CustomIdent for GridLine. r=emilio

So we can avoid calling clone() in to_css().

Differential Revision: https://phabricator.services.mozilla.com/D193838

layout/generic/nsGridContainerFrame.cpp

@@ -5019,7 +5019,7 @@ void nsGridContainerFrame::Grid::PlaceGridItems(
       // name of the lines, knowing that the line placement algorithm will
       // add the -start and -end suffixes as appropriate for layout.
       StyleGridLine lineStartAndEnd;
-      lineStartAndEnd.ident = areaInfo.name;
+      lineStartAndEnd.ident._0 = areaInfo.name;
 
       LineRange columnLines =
           ResolveLineRange(lineStartAndEnd, lineStartAndEnd, colLineNameMap,

layout/style/ServoStyleConstsInlines.h

@@ -475,7 +475,7 @@ StyleGradient::ColorInterpolationMethod() const {
 
 template <typename Integer>
 inline StyleGenericGridLine<Integer>::StyleGenericGridLine()
-    : ident(do_AddRef(static_cast<nsAtom*>(nsGkAtoms::_empty))),
+    : ident{StyleAtom(do_AddRef(static_cast<nsAtom*>(nsGkAtoms::_empty)))},
       line_num(0),
       is_span(false) {}
 

servo/components/style/values/generics/grid.rs

@@ -8,7 +8,7 @@
 use crate::parser::{Parse, ParserContext};
 use crate::values::specified;
 use crate::values::{CSSFloat, CustomIdent};
-use crate::{Atom, One, Zero};
+use crate::{One, Zero};
 use cssparser::Parser;
 use std::fmt::{self, Write};
 use std::{cmp, usize};
@@ -40,7 +40,7 @@ pub struct GenericGridLine<Integer> {
     /// A custom identifier for named lines, or the empty atom otherwise.
     ///
     /// <https://drafts.csswg.org/css-grid/#grid-placement-slot>
-    pub ident: Atom,
+    pub ident: CustomIdent,
     /// Denotes the nth grid line from grid item's placement.
     ///
     /// This is clamped by MIN_GRID_LINE and MAX_GRID_LINE.
@@ -64,18 +64,18 @@ where
         Self {
             is_span: false,
             line_num: Zero::zero(),
-            ident: atom!(""),
+            ident: CustomIdent(atom!("")),
         }
     }
 
     /// Check whether this `<grid-line>` represents an `auto` value.
     pub fn is_auto(&self) -> bool {
-        self.ident == atom!("") && self.line_num.is_zero() && !self.is_span
+        self.ident.0 == atom!("") && self.line_num.is_zero() && !self.is_span
     }
 
     /// Check whether this `<grid-line>` represents a `<custom-ident>` value.
     pub fn is_ident_only(&self) -> bool {
-        self.ident != atom!("") && self.line_num.is_zero() && !self.is_span
+        self.ident.0 != atom!("") && self.line_num.is_zero() && !self.is_span
     }
 
     /// Check if `self` makes `other` omittable according to the rules at:
@@ -105,11 +105,11 @@ where
 
         // 2. `<custom-ident>`
         if self.is_ident_only() {
-            return CustomIdent(self.ident.clone()).to_css(dest);
+            return self.ident.to_css(dest);
         }
 
         // 3. `[ span && [ <integer [1,∞]> || <custom-ident> ] ]`
-        let has_ident = self.ident != atom!("");
+        let has_ident = self.ident.0 != atom!("");
         if self.is_span {
             dest.write_str("span")?;
             debug_assert!(!self.line_num.is_zero() || has_ident);
@@ -125,7 +125,7 @@ where
 
             if has_ident {
                 dest.write_char(' ')?;
-                CustomIdent(self.ident.clone()).to_css(dest)?;
+                self.ident.to_css(dest)?;
             }
             return Ok(());
         }
@@ -135,7 +135,7 @@ where
         self.line_num.to_css(dest)?;
         if has_ident {
             dest.write_char(' ')?;
-            CustomIdent(self.ident.clone()).to_css(dest)?;
+            self.ident.to_css(dest)?;
         }
         Ok(())
     }
@@ -165,7 +165,7 @@ impl Parse for GridLine<specified::Integer> {
                     return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
                 }
 
-                if !grid_line.line_num.is_zero() || grid_line.ident != atom!("") {
+                if !grid_line.line_num.is_zero() || grid_line.ident.0 != atom!("") {
                     val_before_span = true;
                 }
 
@@ -182,12 +182,12 @@ impl Parse for GridLine<specified::Integer> {
                     cmp::min(value, MAX_GRID_LINE),
                 ));
             } else if let Ok(name) = input.try_parse(|i| CustomIdent::parse(i, &["auto"])) {
-                if val_before_span || grid_line.ident != atom!("") {
+                if val_before_span || grid_line.ident.0 != atom!("") {
                     return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
                 }
                 // NOTE(emilio): `span` is consumed above, so we only need to
                 // reject `auto`.
-                grid_line.ident = name.0;
+                grid_line.ident = name;
             } else {
                 break;
             }
@@ -203,7 +203,7 @@ impl Parse for GridLine<specified::Integer> {
                     // disallow negative integers for grid spans
                     return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
                 }
-            } else if grid_line.ident == atom!("") {
+            } else if grid_line.ident.0 == atom!("") {
                 // integer could be omitted
                 return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
             }

servo/components/style/values/mod.rs

@@ -508,6 +508,7 @@ impl<A: Debug, B: Debug> Debug for Either<A, B> {
 #[derive(
     Clone,
     Debug,
+    Default,
     Eq,
     Hash,
     MallocSizeOf,