Share allocations for singletons (#4794)

2 files changed, 18 insertions, 5 deletions

diff --git a/crates/typst-utils/src/lib.rs b/crates/typst-utils/src/lib.rs
index 754fc70d..4d5f8e0c 100644
--- a/crates/typst-utils/src/lib.rs
+++ b/crates/typst-utils/src/lib.rs
@@ -25,6 +25,9 @@ use std::sync::Arc;
 
 use siphasher::sip128::{Hasher128, SipHasher13};
 
+#[doc(hidden)]
+pub use once_cell;
+
 /// Turn a closure into a struct implementing [`Debug`].
 pub fn debug<F>(f: F) -> impl Debug
 where
diff --git a/crates/typst-utils/src/macros.rs b/crates/typst-utils/src/macros.rs
index dfe0c319..dd60a2e0 100644
--- a/crates/typst-utils/src/macros.rs
+++ b/crates/typst-utils/src/macros.rs
@@ -1,8 +1,18 @@
+/// Create a lazy initialized, globally unique `'static` reference to a value.
+#[macro_export]
+macro_rules! singleton {
+    ($ty:ty, $value:expr) => {{
+        static VALUE: $crate::once_cell::sync::Lazy<$ty> =
+            $crate::once_cell::sync::Lazy::new(|| $value);
+        &*VALUE
+    }};
+}
+
 /// Implement the `Sub` trait based on existing `Neg` and `Add` impls.
 #[macro_export]
 macro_rules! sub_impl {
     ($a:ident - $b:ident -> $c:ident) => {
-        impl std::ops::Sub<$b> for $a {
+        impl ::core::ops::Sub<$b> for $a {
             type Output = $c;
 
             fn sub(self, other: $b) -> $c {
@@ -16,7 +26,7 @@ macro_rules! sub_impl {
 #[macro_export]
 macro_rules! assign_impl {
     ($a:ident += $b:ident) => {
-        impl std::ops::AddAssign<$b> for $a {
+        impl ::core::ops::AddAssign<$b> for $a {
             fn add_assign(&mut self, other: $b) {
                 *self = *self + other;
             }
@@ -24,7 +34,7 @@ macro_rules! assign_impl {
     };
 
     ($a:ident -= $b:ident) => {
-        impl std::ops::SubAssign<$b> for $a {
+        impl ::core::ops::SubAssign<$b> for $a {
             fn sub_assign(&mut self, other: $b) {
                 *self = *self - other;
             }
@@ -32,7 +42,7 @@ macro_rules! assign_impl {
     };
 
     ($a:ident *= $b:ident) => {
-        impl std::ops::MulAssign<$b> for $a {
+        impl ::core::ops::MulAssign<$b> for $a {
             fn mul_assign(&mut self, other: $b) {
                 *self = *self * other;
             }
@@ -40,7 +50,7 @@ macro_rules! assign_impl {
     };
 
     ($a:ident /= $b:ident) => {
-        impl std::ops::DivAssign<$b> for $a {
+        impl ::core::ops::DivAssign<$b> for $a {
             fn div_assign(&mut self, other: $b) {
                 *self = *self / other;
             }