refactor: remove Collector:Allocator supertrait

notes/coll_alloc_supertrait/CONCLUSION.md

@@ -0,0 +1,10 @@
+# Conclusion
+
+date: 2026-03-17
+author: shruti2522
+
+We have decided not to go ahead with `Collector: Allocator`. One of the main
+reasons is that it requires the collector to be non-moving, but the whole point
+of this redesign is to move Boa towards a moving GC, so implementing a feature
+that fundamentally depends on objects never moving works against that goal. The
+rest of the reasoning is documented in `collector_allocator_supertrait.md`.

oscars/Cargo.toml

@@ -4,7 +4,6 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-allocator-api2 = { version = "0.4.0", optional = true }
 hashbrown = "0.16.1"
 oscars_derive = { path = "../oscars_derive", version = "0.1.0" }
 rustc-hash = "2.1.1"
@@ -18,7 +17,7 @@ boa_gc = { git = "https://github.com/boa-dev/boa", branch = "main" }
 [[bench]]
 name = "oscars_vs_boa_gc"
 harness = false
-required-features = ["gc_allocator"]
+required-features = ["mark_sweep"]
 
 [[bench]]
 name = "arena2_vs_mempool3"
@@ -33,5 +32,4 @@ default = ["mark_sweep"]
 std = []
 mark_sweep = []
 mark_sweep2 = ["mark_sweep"]
-gc_allocator = ["dep:allocator-api2", "mark_sweep"]
 thin-vec = ["dep:thin-vec", "mark_sweep"]

oscars/benches/oscars_vs_boa_gc.rs

@@ -1,6 +1,6 @@
 use criterion::{BenchmarkId, Criterion, black_box, criterion_group, criterion_main};
 use oscars::mark_sweep::{
-    Gc as OscarsGc, GcAllocVec, MarkSweepGarbageCollector, cell::GcRefCell as OscarsGcRefCell,
+    Gc as OscarsGc, MarkSweepGarbageCollector, cell::GcRefCell as OscarsGcRefCell,
 };
 
 use boa_gc::{Gc as BoaGc, GcRefCell as BoaGcRefCell, force_collect as boa_force_collect};
@@ -101,99 +101,6 @@ fn bench_collection(c: &mut Criterion) {
     group.finish();
 }
 
-fn bench_vec_create(c: &mut Criterion) {
-    let mut group = c.benchmark_group("vector_creation");
-
-    for size in [10, 100, 1000].iter() {
-        group.bench_with_input(
-            BenchmarkId::new("oscars_gc_allocator", size),
-            size,
-            |b, &size| {
-                let collector = MarkSweepGarbageCollector::default()
-                    .with_page_size(65536)
-                    .with_heap_threshold(262144);
-
-                b.iter(|| {
-                    let vec = GcAllocVec::with_capacity(size, &collector);
-                    let gc_vec = OscarsGc::new_in(OscarsGcRefCell::new(vec), &collector);
-
-                    for i in 0..size {
-                        gc_vec.borrow_mut().push(black_box(i));
-                    }
-
-                    black_box(gc_vec.borrow().len())
-                });
-            },
-        );
-
-        group.bench_with_input(
-            BenchmarkId::new("boa_gc_std_vec", size),
-            size,
-            |b, &size| {
-                b.iter(|| {
-                    let gc_vec = BoaGc::new(BoaGcRefCell::new(Vec::with_capacity(size)));
-                    for i in 0..size {
-                        gc_vec.borrow_mut().push(black_box(i));
-                    }
-                    black_box(gc_vec.borrow().len())
-                });
-            },
-        );
-    }
-
-    group.finish();
-}
-
-fn bench_vec_ptrs(c: &mut Criterion) {
-    let mut group = c.benchmark_group("vec_of_gc_pointers");
-
-    for num_elements in [10, 50, 100].iter() {
-        group.bench_with_input(
-            BenchmarkId::new("oscars", num_elements),
-            num_elements,
-            |b, &num_elements| {
-                let collector = MarkSweepGarbageCollector::default()
-                    .with_page_size(65536)
-                    .with_heap_threshold(262144);
-
-                b.iter(|| {
-                    let vec = GcAllocVec::with_capacity(num_elements, &collector);
-                    let gc_vec = OscarsGc::new_in(OscarsGcRefCell::new(vec), &collector);
-
-                    for i in 0..num_elements {
-                        let inner = OscarsGc::new_in(OscarsGcRefCell::new(i), &collector);
-                        gc_vec.borrow_mut().push(inner);
-                    }
-
-                    let sum: usize = gc_vec.borrow().iter().map(|gc| *gc.borrow()).sum();
-                    black_box(sum)
-                });
-            },
-        );
-
-        group.bench_with_input(
-            BenchmarkId::new("boa_gc", num_elements),
-            num_elements,
-            |b, &num_elements| {
-                b.iter(|| {
-                    let mut vec = Vec::with_capacity(num_elements);
-
-                    for i in 0..num_elements {
-                        let gc = BoaGc::new(BoaGcRefCell::new(i));
-                        vec.push(gc);
-                    }
-
-                    let gc_vec = BoaGc::new(BoaGcRefCell::new(vec));
-                    let sum: usize = gc_vec.borrow().iter().map(|gc| *gc.borrow()).sum();
-                    black_box(sum)
-                });
-            },
-        );
-    }
-
-    group.finish();
-}
-
 fn bench_mixed(c: &mut Criterion) {
     let mut group = c.benchmark_group("mixed_workload");
 
@@ -382,8 +289,6 @@ criterion_group!(
     benches,
     bench_alloc,
     bench_collection,
-    bench_vec_create,
-    bench_vec_ptrs,
     bench_mixed,
     bench_pressure,
     bench_deep,

oscars/src/alloc/arena2/alloc.rs

@@ -339,7 +339,7 @@ impl<'arena> Arena<'arena> {
 
     pub fn get_allocation_data<T>(
         &self,
-        value_ref: &T,
+        _value_ref: &T,
     ) -> Result<ArenaAllocationData, ArenaAllocError> {
         let size = core::mem::size_of::<ArenaHeapItem<T>>();
         let alignment = core::mem::align_of::<ArenaHeapItem<T>>();