Bug 1953074 Upgrade style_traits crate to edition 2021 (r=emilio)

Signed-off-by: Nico Burns <nico@nicoburns.com>

Differential Revision: https://phabricator.services.mozilla.com/D240976

servo/components/style_traits/Cargo.toml

@@ -4,6 +4,7 @@ version = "0.0.1"
 authors = ["The Servo Project Developers"]
 license = "MPL-2.0"
 repository = "https://github.com/servo/stylo"
+edition = "2021"
 publish = false
 
 [lib]
@@ -19,7 +20,6 @@ app_units = "0.7"
 bitflags = "2"
 cssparser = "0.34"
 euclid = "0.22"
-lazy_static = "1"
 malloc_size_of = { path = "../malloc_size_of" }
 malloc_size_of_derive = { path = "../../../xpcom/rust/malloc_size_of_derive" }
 nsstring = {path = "../../../xpcom/rust/nsstring/", optional = true}

servo/components/style_traits/arc_slice.rs

@@ -9,6 +9,7 @@ use serde::ser::{Serialize, Serializer};
 use servo_arc::ThinArc;
 use std::ops::Deref;
 use std::ptr::NonNull;
+use std::sync::LazyLock;
 use std::{iter, mem, hash::{Hash, Hasher}};
 
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps, MallocUnconditionalSizeOf};
@@ -44,12 +45,9 @@ impl<T> Clone for ArcSlice<T> {
     }
 }
 
-lazy_static! {
-    // ThinArc doesn't support alignments greater than align_of::<u64>.
-    static ref EMPTY_ARC_SLICE: ArcSlice<u64> = {
-        ArcSlice::from_iter_leaked(iter::empty())
-    };
-}
+// ThinArc doesn't support alignments greater than align_of::<u64>.
+static EMPTY_ARC_SLICE: LazyLock<ArcSlice<u64>> =
+    LazyLock::new(|| ArcSlice::from_iter_leaked(iter::empty()));
 
 impl<T> Default for ArcSlice<T> {
     #[allow(unsafe_code)]

servo/components/style_traits/lib.rs

@@ -10,31 +10,16 @@
 #![crate_type = "rlib"]
 #![deny(unsafe_code, missing_docs)]
 
-extern crate app_units;
-#[macro_use]
-extern crate bitflags;
-extern crate cssparser;
-extern crate euclid;
-#[macro_use]
-extern crate lazy_static;
-extern crate malloc_size_of;
 #[macro_use]
 extern crate malloc_size_of_derive;
-#[cfg(feature = "gecko")]
-extern crate nsstring;
-extern crate selectors;
 #[macro_use]
 extern crate serde;
-extern crate servo_arc;
-#[cfg(feature = "servo")]
-extern crate servo_atoms;
-extern crate thin_vec;
-extern crate to_shmem;
 #[macro_use]
 extern crate to_shmem_derive;
 #[cfg(feature = "servo")]
- extern crate url;
+extern crate url;
 
+use bitflags::bitflags;
 use cssparser::{CowRcStr, Token};
 use selectors::parser::SelectorParseErrorKind;
 #[cfg(feature = "servo")]