[oscars-integration] Integrate mark_sweep_branded backend

.github/workflows/pull_request.yml

@@ -5,6 +5,7 @@ on:
     branches:
       - main
       - releases/**
+      - dev/oscars-gc
 
 permissions:
   contents: read

.github/workflows/rust.yml

@@ -5,10 +5,12 @@ on:
     branches:
       - main
       - releases/**
+      - dev/oscars-gc
   push:
     branches:
       - main
       - releases/**
+      - dev/oscars-gc
   merge_group:
     types: [checks_requested]
   workflow_dispatch:

.github/workflows/test262.yml

@@ -5,6 +5,7 @@ on:
     branches:
       - main
       - releases/**
+      - dev/oscars-gc
 
 permissions:
   contents: read
@@ -15,6 +16,7 @@ concurrency:
 
 jobs:
   run_test262:
+    if: ${{ github.base_ref != 'dev/oscars-gc' }}
     name: Run the test262 test suite
     runs-on: ubuntu-latest
     timeout-minutes: 60

.github/workflows/webassembly.yml

@@ -5,10 +5,12 @@ on:
     branches:
       - main
       - releases/**
+      - dev/oscars-gc
   push:
     branches:
       - main
       - releases/**
+      - dev/oscars-gc
   merge_group:
     types: [checks_requested]
 

Cargo.toml

@@ -118,6 +118,7 @@ num-integer = "0.1.46"
 ryu-js = "1.0.2"
 tap = "1.0.1"
 thiserror = { version = "2.0.18", default-features = false }
+typeid = "1.0.3"
 dashmap = "6.2.1"
 num_enum = "0.7.6"
 itertools = { version = "0.15.0", default-features = false }
@@ -267,3 +268,6 @@ complexity = { level = "warn", priority = -1 }
 perf = { level = "warn", priority = -1 }
 pedantic = { level = "warn", priority = -1 }
 
+[patch."https://github.com/boa-dev/boa.git"]
+boa_string = { path = "core/string" }
+

core/engine/Cargo.toml

@@ -26,6 +26,7 @@ embedded_lz4 = ["boa_macros/embedded_lz4", "lz4_flex"]
 jsvalue-enum = []
 deser = ["boa_interner/serde", "boa_ast/serde"]
 either = ["dep:either", "boa_gc/either"]
+oscars_backend = ["boa_gc/oscars_backend", "boa_string/oscars_backend"]
 
 # Enables the `Intl` builtin object and bundles a default ICU4X data provider.
 # Prefer this over `intl` if you just want to enable `Intl` without dealing with the

core/engine/src/builtins/eval/mod.rs

@@ -320,10 +320,8 @@ impl Eval {
 
         compiler.compile_statement_list(body.statements(), true, false);
 
-        let code_block = Gc::new(
-            &unsafe { boa_gc::MutationContext::dummy() },
-            compiler.finish(),
-        );
+        let finished = compiler.finish();
+        let code_block = context.alloc(finished);
 
         // Strict calls don't need extensions, since all strict eval calls push a new
         // function environment before evaluating.
@@ -350,9 +348,11 @@ impl Eval {
         {
             let frame = context.vm.frame_mut();
             let global = frame.realm.environment();
-            frame
-                .environments
-                .push_lexical(lexical_scope.num_bindings_non_local(), global);
+            frame.environments.push_lexical(
+                lexical_scope.num_bindings_non_local(),
+                global,
+                unsafe { boa_gc::MutationContext::global() },
+            );
         }
 
         context

core/engine/src/builtins/finalization_registry/mod.rs

@@ -158,10 +158,7 @@ impl BuiltInConstructor for FinalizationRegistry {
             },
         );
 
-        let weak_registry = WeakGc::new(
-            &unsafe { boa_gc::MutationContext::dummy() },
-            registry.inner(),
-        );
+        let weak_registry = WeakGc::new(context.gc_collector(), registry.inner());
 
         {
             async fn inner_cleanup(
@@ -174,7 +171,7 @@ impl BuiltInConstructor for FinalizationRegistry {
                 };
 
                 let Some(registry) = weak_registry
-                    .upgrade(&unsafe { boa_gc::MutationContext::dummy() })
+                    .upgrade(&unsafe { boa_gc::MutationContext::global() })
                     .map(JsObject::from_inner)
                 else {
                     return Ok(JsValue::undefined());
@@ -205,7 +202,7 @@ impl FinalizationRegistry {
     /// [`FinalizationRegistry.prototype.register ( target, heldValue [ , unregisterToken ] )`][spec]
     ///
     /// [spec]: https://tc39.es/ecma262/sec-finalization-registry.prototype.register
-    fn register(this: &JsValue, args: &[JsValue], _context: &mut Context) -> JsResult<JsValue> {
+    fn register(this: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
         // 1. Let finalizationRegistry be the this value.
         // 2. Perform ? RequireInternalSlot(finalizationRegistry, [[Cells]]).
         let this = this.as_object();
@@ -257,10 +254,7 @@ impl FinalizationRegistry {
         //
         // TODO: support Symbols
         let unregister_token = match unregister_token.variant() {
-            JsVariant::Object(obj) => Some(WeakGc::new(
-                &unsafe { boa_gc::MutationContext::dummy() },
-                obj.inner(),
-            )),
+            JsVariant::Object(obj) => Some(WeakGc::new(context.gc_collector(), obj.inner())),
             // b. Set unregisterToken to empty.
             JsVariant::Undefined => None,
             // a. If unregisterToken is not undefined, throw a TypeError exception.
@@ -275,7 +269,7 @@ impl FinalizationRegistry {
         // 6. Let cell be the Record { [[WeakRefTarget]]: target, [[HeldValue]]: heldValue, [[UnregisterToken]]: unregisterToken }.
         let cell = RegistryCell {
             target: Ephemeron::new(
-                &unsafe { boa_gc::MutationContext::dummy() },
+                context.gc_collector(),
                 target_obj.inner(),
                 CleanupSignaler(Cell::new(Some(
                     registry.cleanup_notifier.clone().downgrade(),
@@ -295,7 +289,7 @@ impl FinalizationRegistry {
     /// [`FinalizationRegistry.prototype.unregister ( unregisterToken )`][spec]
     ///
     /// [spec]: https://tc39.es/ecma262/#sec-finalization-registry.prototype.unregister
-    fn unregister(this: &JsValue, args: &[JsValue], _context: &mut Context) -> JsResult<JsValue> {
+    fn unregister(this: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
         // 1. Let finalizationRegistry be the this value.
         // 2. Perform ? RequireInternalSlot(finalizationRegistry, [[Cells]]).
         let this = this.as_object();
@@ -338,19 +332,17 @@ impl FinalizationRegistry {
 
             // a. If cell.[[UnregisterToken]] is not empty and SameValue(cell.[[UnregisterToken]], unregisterToken) is true, then
             if let Some(tok) = cell.unregister_token.as_ref()
-                && let Some(tok) = tok.upgrade(&unsafe { boa_gc::MutationContext::dummy() })
+                && let Some(tok) = tok.upgrade(context.gc_collector())
                 && Gc::ptr_eq(&tok, unregister_token)
             {
                 // i. Remove cell from finalizationRegistry.[[Cells]].
                 let cell = registry.cells.swap_remove(i);
-                let _key = cell
-                    .target
-                    .key(&unsafe { boa_gc::MutationContext::dummy() });
+                let _key = cell.target.key(context.gc_collector());
 
                 // TODO: it might be better to add a special ref for the value that
                 // also preserves the original key instead.
                 cell.target
-                    .value(&unsafe { boa_gc::MutationContext::dummy() })
+                    .value(context.gc_collector())
                     .and_then(|v| v.0.take());
 
                 // ii. Set removed to true.

core/engine/src/builtins/finalization_registry/tests.rs

@@ -1,3 +1,4 @@
+#[cfg(not(feature = "oscars_backend"))]
 mod miri {
 
     use indoc::indoc;

core/engine/src/builtins/function/arguments.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::trivially_copy_pass_by_ref)]
+#![allow(clippy::needless_pass_by_value)]
 use crate::{
     Context, JsData, JsExpect, JsResult, JsValue,
     bytecompiler::ToJsString,
@@ -124,7 +126,7 @@ impl MappedArguments {
             .get(index as usize)
             .copied()
             .flatten()?;
-        self.environment.get(binding_index)
+        (*self.environment).get(binding_index)
     }
 
     /// Set the value of the binding at the given index in the function environment.

core/engine/src/builtins/function/mod.rs

@@ -1073,7 +1073,9 @@ pub(crate) fn function_call(
     if has_binding_identifier {
         let frame = context.vm.frame_mut();
         let global = frame.realm.environment();
-        let index = frame.environments.push_lexical(1, global);
+        let index = frame
+            .environments
+            .push_lexical(1, global, unsafe { boa_gc::MutationContext::global() });
         frame.environments.put_lexical_value(
             BindingLocatorScope::Stack(index),
             0,
@@ -1091,6 +1093,7 @@ pub(crate) fn function_call(
             scope,
             FunctionSlots::new(this, function_object.clone(), None),
             global,
+            unsafe { boa_gc::MutationContext::global() },
         );
     }
 
@@ -1181,7 +1184,9 @@ fn function_construct(
     if has_binding_identifier {
         let frame = context.vm.frame_mut();
         let global = frame.realm.environment();
-        let index = frame.environments.push_lexical(1, global);
+        let index = frame
+            .environments
+            .push_lexical(1, global, unsafe { boa_gc::MutationContext::global() });
         frame.environments.put_lexical_value(
             BindingLocatorScope::Stack(index),
             0,
@@ -1210,6 +1215,7 @@ fn function_construct(
                 ),
             ),
             global,
+            unsafe { boa_gc::MutationContext::global() },
         );
     }
 

core/engine/src/builtins/generator/mod.rs

@@ -46,7 +46,7 @@ pub(crate) enum GeneratorState {
 // Need to manually implement, since `Trace` adds a `Drop` impl which disallows destructuring.
 unsafe impl Trace for GeneratorState {
     custom_trace!(this, mark, {
-        match &this {
+        match this {
             Self::SuspendedStart { context } | Self::SuspendedYield { context } => mark(context),
             Self::Executing | Self::Completed => {}
         }

core/engine/src/builtins/intl/list_format/mod.rs

@@ -329,7 +329,7 @@ impl ListFormat {
                 part: writeable::Part,
                 mut f: impl FnMut(&mut Self::SubPartsWrite) -> core::fmt::Result,
             ) -> core::fmt::Result {
-                assert!(part.category == "list");
+                assert_eq!(part.category, "list");
                 let mut string = WriteString(String::new());
                 f(&mut string)?;
                 if !string.0.is_empty() {

core/engine/src/builtins/intl/locale/mod.rs

@@ -349,14 +349,17 @@ impl Locale {
         // 1. Let loc be the this value.
         // 2. Perform ? RequireInternalSlot(loc, [[InitializedLocale]]).
         let object = this.as_object();
+        // Under `oscars_backend`, `downcast_ref` returns `GcRef<'_, Locale>`.
+        // Deref through the guard before cloning to get an owned `icu_locale::Locale`.
+        // This is required because `GcRef<'_, Locale>` doesn't implement `NativeObject`.
         let mut loc = object
             .as_ref()
             .and_then(|o| o.downcast_ref::<icu_locale::Locale>())
             .ok_or_else(|| {
                 JsNativeError::typ()
                     .with_message("`Locale.maximize` can only be called on a `Locale` object")
-            })?
-            .clone();
+            })
+            .map(|r| (*r).clone())?;
 
         // 3. Let maximal be the result of the Add Likely Subtags algorithm applied to loc.[[Locale]]. If an error is signaled, set maximal to loc.[[Locale]].
         context
@@ -387,15 +390,17 @@ impl Locale {
         // 1. Let loc be the this value.
         // 2. Perform ? RequireInternalSlot(loc, [[InitializedLocale]]).
         let object = this.as_object();
+        // Under `oscars_backend`, `downcast_ref` returns `GcRef<'_, Locale>`.
+        // Deref through the guard before cloning to get an owned `icu_locale::Locale`.
         let mut loc = object
             .as_ref()
             .and_then(|o| o.downcast_ref::<icu_locale::Locale>())
             .ok_or_else(|| {
                 JsNativeError::typ().with_message(
                     "`Locale.prototype.minimize` can only be called on a `Locale` object",
                 )
-            })?
-            .clone();
+            })
+            .map(|r| (*r).clone())?;
 
         // 3. Let minimal be the result of the Remove Likely Subtags algorithm applied to loc.[[Locale]]. If an error is signaled, set minimal to loc.[[Locale]].
         context

core/engine/src/builtins/intl/locale/utils.rs

@@ -54,7 +54,9 @@ pub(crate) fn locale_from_value(tag: &JsValue, context: &mut Context) -> JsResul
     if let Some(tag) = object.as_ref().and_then(|obj| obj.downcast_ref::<Locale>()) {
         // 1. Let tag be kValue.[[Locale]].
         // No need to canonicalize since all `Locale` objects should already be canonicalized.
-        return Ok(tag.clone());
+        // Under `oscars_backend`, `downcast_ref` returns `GcRef<'_, Locale>`.
+        // Deref through the guard before cloning to clone the `Locale` value, not the wrapper.
+        return Ok((*tag).clone());
     }
 
     // iv. Else,

core/engine/src/builtins/json/mod.rs

@@ -307,10 +307,8 @@ impl Json {
                 SourcePath::Json,
             );
             compiler.compile_statement_list(script.statements(), true, false);
-            Gc::new(
-                &unsafe { boa_gc::MutationContext::dummy() },
-                compiler.finish(),
-            )
+            let finished = compiler.finish();
+            context.alloc(finished)
         };
 
         let realm = context.realm().clone();
@@ -815,7 +813,10 @@ impl Json {
             // d. Else if value has a [[BigIntData]] internal slot, then
             else if let Some(bigint) = obj.downcast_ref::<JsBigInt>() {
                 // i. Set value to value.[[BigIntData]].
-                value = bigint.clone().into();
+                // SAFETY: Under oscars_backend, `downcast_ref` returns a `GcRef<'_, JsBigInt>`.
+                // We must deref through the guard before calling `.clone()` so that we clone
+                // the inner `JsBigInt`, not the `GcRef` wrapper.
+                value = (*bigint).clone().into();
             }
             // e. Else if value has a [[IsRawJSON]] internal slot, then
             else if obj.is::<RawJson>() {