feat(ecmascript): WeakMap and GC ephemerons (#902)

* feat(ecmascript): WeakMap

* perf(gc): Store mark bits in a single allocation

* feat(gc): Ephemerons

* chore: update dylint and nightly version

Author: aapoalas

.github/workflows/ci.yml

@@ -37,7 +37,7 @@ jobs:
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@nightly
         with:
-          toolchain: nightly-2025-05-14
+          toolchain: nightly-2025-10-31
           components: rustfmt, clippy, llvm-tools-preview, rustc-dev
       - name: Cache on ${{ github.ref_name }}
         uses: Swatinem/rust-cache@v2
@@ -52,7 +52,7 @@ jobs:
       - name: Clippy
         run: |
           cargo +stable clippy --all-targets -- -D warnings
-          cargo +nightly-2025-05-14 clippy --all-targets --all-features -- -D warnings
+          cargo +nightly-2025-10-31 clippy --all-targets --all-features -- -D warnings
       - name: Dylint tests
         working-directory: nova_lint
         run: cargo test

nova_lint/Cargo.toml

@@ -25,11 +25,11 @@ name = "gc_scope_is_only_passed_by_value"
 path = "ui/gc_scope_is_only_passed_by_value.rs"
 
 [dependencies]
-clippy_utils = { git = "https://github.com/rust-lang/rust-clippy", rev = "0450db33a5d8587f7c1d4b6d233dac963605766b" }
-dylint_linting = { version = "4.1.0", features = ["constituent"] }
+clippy_utils = { git = "https://github.com/rust-lang/rust-clippy", rev = "c936595d17413c1f08e162e117e504fb4ed126e4" }
+dylint_linting = { version = "5.0.0", features = ["constituent"] }
 
 [dev-dependencies]
-dylint_testing = "4.1.0"
+dylint_testing = "5.0.0"
 nova_vm = { path = "../nova_vm" }
 
 [package.metadata.rust-analyzer]

nova_lint/rust-toolchain.toml nova_lint/rust-toolchainnova_lint/rust-toolchain.toml renamed to nova_lint/rust-toolchain

@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2025-05-14"
+channel = "nightly-2025-10-31"
 components = ["llvm-tools-preview", "rustc-dev"]

nova_vm/src/ecmascript/abstract_operations/operations_on_objects.rs

@@ -895,7 +895,6 @@ pub(crate) fn set_integrity_level<'a, T: Level>(
                 // 3. Perform ? DefinePropertyOrThrow(O, k, desc).
                 define_property_or_throw(agent, o, k.get(agent), desc, gc.reborrow()).unbind()?;
             }
-            i += 1;
         }
     }
     // 6. Return true.

nova_vm/src/ecmascript/builtins/array.rs

@@ -183,7 +183,7 @@ impl<'a> Array<'a> {
         create_array_from_list(agent, elements, gc)
     }
 
-    pub(crate) fn get_index(self) -> usize {
+    pub(crate) const fn get_index(self) -> usize {
         self.0.into_index()
     }
 

nova_vm/src/ecmascript/builtins/array/data.rs

@@ -56,23 +56,3 @@ impl HeapMarkAndSweep for ArrayHeapDataMut<'_, 'static> {
         object_index.sweep_values(compactions);
     }
 }
-
-impl HeapMarkAndSweep for ArrayHeapData<'static> {
-    fn mark_values(&self, queues: &mut WorkQueues) {
-        let Self {
-            object_index,
-            elements,
-        } = self;
-        object_index.mark_values(queues);
-        elements.mark_values(queues);
-    }
-
-    fn sweep_values(&mut self, compactions: &CompactionLists) {
-        let Self {
-            object_index,
-            elements,
-        } = self;
-        object_index.sweep_values(compactions);
-        elements.sweep_values(compactions);
-    }
-}

nova_vm/src/ecmascript/builtins/data_view/data.rs

@@ -16,6 +16,7 @@ use crate::{
     heap::{CompactionLists, HeapMarkAndSweep, WorkQueues},
 };
 
+#[derive(Debug)]
 pub struct DataViewRecord<'a> {
     pub(crate) object_index: Option<OrdinaryObject<'a>>,
     // TODO: Add a helper function for a u32::MAX value which signifies an a under-construction value:
@@ -41,6 +42,7 @@ impl Default for DataViewRecord<'_> {
 }
 
 #[cfg(feature = "shared-array-buffer")]
+#[derive(Debug)]
 pub struct SharedDataViewRecord<'a> {
     pub(crate) object_index: Option<OrdinaryObject<'a>>,
     // TODO: Add a helper function for a u32::MAX value which signifies an a under-construction value:

nova_vm/src/ecmascript/builtins/indexed_collections/array_objects/array_iterator_objects/array_iterator.rs

@@ -30,7 +30,7 @@ impl<'a> ArrayIterator<'a> {
         Self(BaseIndex::from_u32_index(0))
     }
 
-    pub(crate) fn get_index(self) -> usize {
+    pub(crate) const fn get_index(self) -> usize {
         self.0.into_index()
     }
 

nova_vm/src/ecmascript/builtins/keyed_collections/map_objects/map_constructor.rs

@@ -440,14 +440,15 @@ pub fn add_entries_from_iterable_map_constructor<'a>(
 /// > element array-like object whose first element is a value that will be used
 /// > as a Map key and whose second element is the value to associate with that
 /// > key.
-pub(crate) fn add_entries_from_iterable<'a>(
+pub(crate) fn add_entries_from_iterable<'a, T: Into<Object<'a>> + TryFrom<Object<'a>>>(
     agent: &mut Agent,
-    target: Map,
+    target: T,
     iterable: Value,
     adder: Function,
     mut gc: GcScope<'a, '_>,
-) -> JsResult<'a, Map<'a>> {
+) -> JsResult<'a, T> {
     let nogc = gc.nogc();
+    let target: Object = target.into();
     let target = target.scope(agent, nogc);
     let iterable = iterable.bind(nogc);
     let adder = adder.scope(agent, nogc);
@@ -482,7 +483,11 @@ pub(crate) fn add_entries_from_iterable<'a>(
         .bind(gc.nogc());
         // b. If next is DONE, return target.
         let Some(next) = next else {
-            return Ok(target.get(agent).bind(gc.into_nogc()));
+            // SAFETY: not shared.
+            let target = unsafe { target.take(agent).bind(gc.into_nogc()) };
+            // SAFETY: passed in type is still the same type.
+            let target = unsafe { T::try_from(target).unwrap_unchecked() };
+            return Ok(target);
         };
         // c. If next is not an Object, then
         let Ok(next) = Object::try_from(next) else {

nova_vm/src/ecmascript/builtins/keyed_collections/map_objects/map_iterator_objects/map_iterator.rs

@@ -34,7 +34,7 @@ impl MapIterator<'_> {
         Self(BaseIndex::from_u32_index(0))
     }
 
-    pub(crate) fn get_index(self) -> usize {
+    pub(crate) const fn get_index(self) -> usize {
         self.0.into_index()
     }