Improve typing of `DataView` and related objects (#3626)

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

@@ -16,6 +16,8 @@ pub(crate) mod utils;
 #[cfg(test)]
 mod tests;
 
+use std::ops::{Deref, DerefMut};
+
 pub use shared::SharedArrayBuffer;
 
 use crate::{
@@ -23,7 +25,7 @@ use crate::{
     context::intrinsics::{Intrinsics, StandardConstructor, StandardConstructors},
     error::JsNativeError,
     js_string,
-    object::{internal_methods::get_prototype_from_constructor, JsObject},
+    object::{internal_methods::get_prototype_from_constructor, JsObject, Object},
     property::Attribute,
     realm::Realm,
     string::common::StaticJsStrings,
@@ -31,7 +33,7 @@ use crate::{
     value::IntegerOrInfinity,
     Context, JsArgs, JsData, JsResult, JsString, JsValue,
 };
-use boa_gc::{Finalize, Trace};
+use boa_gc::{Finalize, GcRef, GcRefMut, Trace};
 use boa_profiler::Profiler;
 
 use self::utils::{SliceRef, SliceRefMut};
@@ -41,16 +43,20 @@ use super::{
 };
 
 #[derive(Debug, Clone, Copy)]
-pub(crate) enum BufferRef<'a> {
-    Buffer(&'a ArrayBuffer),
-    SharedBuffer(&'a SharedArrayBuffer),
+pub(crate) enum BufferRef<B, S> {
+    Buffer(B),
+    SharedBuffer(S),
 }
 
-impl BufferRef<'_> {
+impl<B, S> BufferRef<B, S>
+where
+    B: Deref<Target = ArrayBuffer>,
+    S: Deref<Target = SharedArrayBuffer>,
+{
     pub(crate) fn data(&self) -> Option<SliceRef<'_>> {
         match self {
-            Self::Buffer(buf) => buf.data().map(SliceRef::Slice),
-            Self::SharedBuffer(buf) => Some(SliceRef::AtomicSlice(buf.data())),
+            Self::Buffer(buf) => buf.deref().data().map(SliceRef::Slice),
+            Self::SharedBuffer(buf) => Some(SliceRef::AtomicSlice(buf.deref().data())),
         }
     }
 
@@ -60,16 +66,96 @@ impl BufferRef<'_> {
 }
 
 #[derive(Debug)]
-pub(crate) enum BufferRefMut<'a> {
-    Buffer(&'a mut ArrayBuffer),
-    SharedBuffer(&'a mut SharedArrayBuffer),
+pub(crate) enum BufferRefMut<B, S> {
+    Buffer(B),
+    SharedBuffer(S),
 }
 
-impl BufferRefMut<'_> {
+impl<B, S> BufferRefMut<B, S>
+where
+    B: DerefMut<Target = ArrayBuffer>,
+    S: DerefMut<Target = SharedArrayBuffer>,
+{
     pub(crate) fn data_mut(&mut self) -> Option<SliceRefMut<'_>> {
         match self {
-            Self::Buffer(buf) => buf.data_mut().map(SliceRefMut::Slice),
-            Self::SharedBuffer(buf) => Some(SliceRefMut::AtomicSlice(buf.data())),
+            Self::Buffer(buf) => buf.deref_mut().data_mut().map(SliceRefMut::Slice),
+            Self::SharedBuffer(buf) => Some(SliceRefMut::AtomicSlice(buf.deref_mut().data())),
+        }
+    }
+}
+
+/// A `JsObject` containing a bytes buffer as its inner data.
+#[derive(Debug, Clone, Trace, Finalize)]
+#[boa_gc(unsafe_no_drop)]
+pub(crate) enum BufferObject {
+    Buffer(JsObject<ArrayBuffer>),
+    SharedBuffer(JsObject<SharedArrayBuffer>),
+}
+
+impl From<BufferObject> for JsObject {
+    fn from(value: BufferObject) -> Self {
+        match value {
+            BufferObject::Buffer(buf) => buf.upcast(),
+            BufferObject::SharedBuffer(buf) => buf.upcast(),
+        }
+    }
+}
+
+impl From<BufferObject> for JsValue {
+    fn from(value: BufferObject) -> Self {
+        JsValue::from(JsObject::from(value))
+    }
+}
+
+impl BufferObject {
+    /// Gets the buffer data of the object.
+    #[inline]
+    #[must_use]
+    pub(crate) fn as_buffer(
+        &self,
+    ) -> BufferRef<GcRef<'_, ArrayBuffer>, GcRef<'_, SharedArrayBuffer>> {
+        match self {
+            Self::Buffer(buf) => BufferRef::Buffer(GcRef::map(buf.borrow(), |o| &o.data)),
+            Self::SharedBuffer(buf) => {
+                BufferRef::SharedBuffer(GcRef::map(buf.borrow(), |o| &o.data))
+            }
+        }
+    }
+
+    /// Gets the mutable buffer data of the object
+    #[inline]
+    pub(crate) fn as_buffer_mut(
+        &self,
+    ) -> BufferRefMut<
+        GcRefMut<'_, Object<ArrayBuffer>, ArrayBuffer>,
+        GcRefMut<'_, Object<SharedArrayBuffer>, SharedArrayBuffer>,
+    > {
+        match self {
+            Self::Buffer(buf) => {
+                BufferRefMut::Buffer(GcRefMut::map(buf.borrow_mut(), |o| &mut o.data))
+            }
+            Self::SharedBuffer(buf) => {
+                BufferRefMut::SharedBuffer(GcRefMut::map(buf.borrow_mut(), |o| &mut o.data))
+            }
+        }
+    }
+
+    /// Returns `true` if the buffer objects point to the same buffer.
+    #[inline]
+    pub(crate) fn equals(lhs: &Self, rhs: &Self) -> bool {
+        match (lhs, rhs) {
+            (BufferObject::Buffer(lhs), BufferObject::Buffer(rhs)) => JsObject::equals(lhs, rhs),
+            (BufferObject::SharedBuffer(lhs), BufferObject::SharedBuffer(rhs)) => {
+                if JsObject::equals(lhs, rhs) {
+                    return true;
+                }
+
+                let lhs = lhs.borrow();
+                let rhs = rhs.borrow();
+
+                std::ptr::eq(lhs.data.data().as_ptr(), rhs.data.data().as_ptr())
+            }
+            _ => false,
         }
     }
 }

core/engine/src/builtins/array_buffer/shared.rs

@@ -125,7 +125,9 @@ impl BuiltInConstructor for SharedArrayBuffer {
         let byte_length = args.get_or_undefined(0).to_index(context)?;
 
         // 3. Return ? AllocateSharedArrayBuffer(NewTarget, byteLength, requestedMaxByteLength).
-        Ok(Self::allocate(new_target, byte_length, context)?.into())
+        Ok(Self::allocate(new_target, byte_length, context)?
+            .upcast()
+            .into())
     }
 }
 
@@ -256,7 +258,7 @@ impl SharedArrayBuffer {
         constructor: &JsValue,
         byte_length: u64,
         context: &mut Context,
-    ) -> JsResult<JsObject> {
+    ) -> JsResult<JsObject<SharedArrayBuffer>> {
         // TODO:
         // 1. Let slots be « [[ArrayBufferData]] ».
         // 2. If maxByteLength is present and maxByteLength is not empty, let allocatingGrowableBuffer
@@ -291,11 +293,7 @@ impl SharedArrayBuffer {
 
         // 10. Else,
         //     a. Set obj.[[ArrayBufferByteLength]] to byteLength.
-        let obj = JsObject::from_proto_and_data_with_shared_shape(
-            context.root_shape(),
-            prototype,
-            Self { data },
-        );
+        let obj = JsObject::new(context.root_shape(), prototype, Self { data });
 
         // 11. Return obj.
         Ok(obj)

core/engine/src/builtins/array_buffer/utils.rs

@@ -3,7 +3,6 @@
 use std::{ptr, slice::SliceIndex, sync::atomic};
 
 use portable_atomic::AtomicU8;
-use sptr::Strict;
 
 use crate::{
     builtins::typed_array::{ClampedU8, Element, TypedArrayElement, TypedArrayKind},
@@ -41,7 +40,9 @@ impl SliceRef<'_> {
     }
 
     /// Gets the starting address of this `SliceRef`.
+    #[cfg(debug_assertions)]
     pub(crate) fn addr(&self) -> usize {
+        use sptr::Strict;
         match self {
             Self::Slice(buf) => buf.as_ptr().addr(),
             Self::AtomicSlice(buf) => buf.as_ptr().addr(),
@@ -68,7 +69,8 @@ impl SliceRef<'_> {
 
             // 1. Assert: IsDetachedBuffer(arrayBuffer) is false.
             // 2. Assert: There are sufficient bytes in arrayBuffer starting at byteIndex to represent a value of type.
-            if cfg!(debug_assertions) {
+            #[cfg(debug_assertions)]
+            {
                 assert!(buffer.len() >= std::mem::size_of::<T>());
                 assert_eq!(buffer.addr() % std::mem::align_of::<T>(), 0);
             }
@@ -178,6 +180,7 @@ pub(crate) enum SliceRefMut<'a> {
 
 impl SliceRefMut<'_> {
     /// Gets the byte length of this `SliceRefMut`.
+    #[cfg(debug_assertions)]
     pub(crate) fn len(&self) -> usize {
         match self {
             Self::Slice(buf) => buf.len(),
@@ -201,7 +204,9 @@ impl SliceRefMut<'_> {
     }
 
     /// Gets the starting address of this `SliceRefMut`.
+    #[cfg(debug_assertions)]
     pub(crate) fn addr(&self) -> usize {
+        use sptr::Strict;
         match self {
             Self::Slice(buf) => buf.as_ptr().addr(),
             Self::AtomicSlice(buf) => buf.as_ptr().addr(),
@@ -236,7 +241,8 @@ impl SliceRefMut<'_> {
             // 1. Assert: IsDetachedBuffer(arrayBuffer) is false.
             // 2. Assert: There are sufficient bytes in arrayBuffer starting at byteIndex to represent a value of type.
             // 3. Assert: value is a BigInt if IsBigIntElementType(type) is true; otherwise, value is a Number.
-            if cfg!(debug_assertions) {
+            #[cfg(debug_assertions)]
+            {
                 assert!(buffer.len() >= std::mem::size_of::<T>());
                 assert_eq!(buffer.addr() % std::mem::align_of::<T>(), 0);
             }
@@ -345,7 +351,8 @@ unsafe fn copy_shared_to_shared_backwards(src: &[AtomicU8], dest: &[AtomicU8], c
 ///   (you cannot borrow and mutably borrow a slice at the same time), but cannot be guaranteed
 ///   for atomic slices.
 pub(crate) unsafe fn memcpy(src: SliceRef<'_>, dest: SliceRefMut<'_>, count: usize) {
-    if cfg!(debug_assertions) {
+    #[cfg(debug_assertions)]
+    {
         assert!(src.len() >= count);
         assert!(dest.len() >= count);
         let src_range = src.addr()..src.addr() + src.len();
@@ -387,7 +394,8 @@ pub(crate) unsafe fn memcpy(src: SliceRef<'_>, dest: SliceRefMut<'_>, count: usi
 /// - `buffer` must contain at least `from + count` bytes to be read.
 /// - `buffer` must contain at least `to + count` bytes to be written.
 pub(crate) unsafe fn memmove(buffer: SliceRefMut<'_>, from: usize, to: usize, count: usize) {
-    if cfg!(debug_assertions) {
+    #[cfg(debug_assertions)]
+    {
         assert!(from + count <= buffer.len());
         assert!(to + count <= buffer.len());
     }

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

@@ -24,7 +24,7 @@ use boa_gc::GcRef;
 use boa_profiler::Profiler;
 
 use super::{
-    array_buffer::{BufferRef, SharedArrayBuffer},
+    array_buffer::BufferRef,
     typed_array::{Atomic, ContentType, Element, TypedArray, TypedArrayElement, TypedArrayKind},
     BuiltInBuilder, IntrinsicObject,
 };
@@ -80,10 +80,7 @@ macro_rules! atomic_op {
             let value = ii.kind().get_element(value, context)?;
 
             // revalidate
-            let mut buffer = ii.viewed_array_buffer().borrow_mut();
-            let mut buffer = buffer
-                .as_buffer_mut()
-                .expect("integer indexed object must contain a valid buffer");
+            let mut buffer = ii.viewed_array_buffer().as_buffer_mut();
             let Some(mut data) = buffer.data_mut() else {
                 return Err(JsNativeError::typ()
                     .with_message("cannot execute atomic operation in detached buffer")
@@ -168,10 +165,7 @@ impl Atomics {
         let pos = validate_atomic_access(&ii, index, context)?;
 
         // 2. Perform ? RevalidateAtomicAccess(typedArray, indexedPosition).
-        let buffer = ii.viewed_array_buffer().borrow();
-        let buffer = buffer
-            .as_buffer()
-            .expect("integer indexed object must contain a valid buffer");
+        let buffer = ii.viewed_array_buffer().as_buffer();
         let Some(data) = buffer.data() else {
             return Err(JsNativeError::typ()
                 .with_message("cannot execute atomic operation in detached buffer")
@@ -217,10 +211,7 @@ impl Atomics {
         let value = ii.kind().get_element(&converted, context)?;
 
         // 4. Perform ? RevalidateAtomicAccess(typedArray, indexedPosition).
-        let mut buffer = ii.viewed_array_buffer().borrow_mut();
-        let mut buffer = buffer
-            .as_buffer_mut()
-            .expect("integer indexed object must contain a valid buffer");
+        let mut buffer = ii.viewed_array_buffer().as_buffer_mut();
         let Some(mut buffer) = buffer.data_mut() else {
             return Err(JsNativeError::typ()
                 .with_message("cannot execute atomic operation in detached buffer")
@@ -269,10 +260,7 @@ impl Atomics {
             .to_bytes();
 
         // 6. Perform ? RevalidateAtomicAccess(typedArray, indexedPosition).
-        let mut buffer = ii.viewed_array_buffer().borrow_mut();
-        let mut buffer = buffer
-            .as_buffer_mut()
-            .expect("integer indexed object must contain a valid buffer");
+        let mut buffer = ii.viewed_array_buffer().as_buffer_mut();
         let Some(mut data) = buffer.data_mut() else {
             return Err(JsNativeError::typ()
                 .with_message("cannot execute atomic operation in detached buffer")
@@ -403,10 +391,7 @@ impl Atomics {
 
         // 1. Let buffer be ? ValidateIntegerTypedArray(typedArray, true).
         let ii = validate_integer_typed_array(array, true)?;
-        let buffer = ii.viewed_array_buffer().borrow();
-        let buffer = buffer
-            .as_buffer()
-            .expect("integer indexed object must contain a valid buffer");
+        let buffer = ii.viewed_array_buffer().as_buffer();
 
         // 2. If IsSharedArrayBuffer(buffer) is false, throw a TypeError exception.
         let BufferRef::SharedBuffer(buffer) = buffer else {
@@ -451,10 +436,10 @@ impl Atomics {
         // SAFETY: the validity of `addr` is verified by our call to `validate_atomic_access`.
         let result = unsafe {
             if ii.kind() == TypedArrayKind::BigInt64 {
-                futex::wait(buffer, offset, value, timeout)?
+                futex::wait(&buffer, offset, value, timeout)?
             } else {
                 // value must fit into `i32` since it came from an `i32` above.
-                futex::wait(buffer, offset, value as i32, timeout)?
+                futex::wait(&buffer, offset, value as i32, timeout)?
             }
         };
 
@@ -496,13 +481,11 @@ impl Atomics {
         // 4. Let buffer be typedArray.[[ViewedArrayBuffer]].
         // 5. Let block be buffer.[[ArrayBufferData]].
         // 6. If IsSharedArrayBuffer(buffer) is false, return +0𝔽.
-        let buffer = ii.viewed_array_buffer();
-        let buffer = buffer.borrow();
-        let Some(shared) = buffer.downcast_ref::<SharedArrayBuffer>() else {
+        let BufferRef::SharedBuffer(shared) = ii.viewed_array_buffer().as_buffer() else {
             return Ok(0.into());
         };
 
-        let count = futex::notify(shared, offset, count)?;
+        let count = futex::notify(&shared, offset, count)?;
 
         // 12. Let n be the number of elements in S.
         // 13. Return 𝔽(n).

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

@@ -26,7 +26,10 @@ use boa_gc::{Finalize, Trace};
 use bytemuck::{bytes_of, bytes_of_mut};
 
 use super::{
-    array_buffer::utils::{memcpy, SliceRef, SliceRefMut},
+    array_buffer::{
+        utils::{memcpy, SliceRef, SliceRefMut},
+        BufferObject,
+    },
     typed_array::{self, TypedArrayElement},
     BuiltInBuilder, BuiltInConstructor, IntrinsicObject,
 };
@@ -34,7 +37,7 @@ use super::{
 /// The internal representation of a `DataView` object.
 #[derive(Debug, Clone, Trace, Finalize, JsData)]
 pub struct DataView {
-    pub(crate) viewed_array_buffer: JsObject,
+    pub(crate) viewed_array_buffer: BufferObject,
     pub(crate) byte_length: u64,
     pub(crate) byte_offset: u64,
 }
@@ -135,11 +138,6 @@ impl BuiltInConstructor for DataView {
     ) -> JsResult<JsValue> {
         let byte_length = args.get_or_undefined(2);
 
-        let buffer_obj = args
-            .get_or_undefined(0)
-            .as_object()
-            .ok_or_else(|| JsNativeError::typ().with_message("buffer must be an ArrayBuffer"))?;
-
         // 1. If NewTarget is undefined, throw a TypeError exception.
         if new_target.is_undefined() {
             return Err(JsNativeError::typ()
@@ -147,15 +145,19 @@ impl BuiltInConstructor for DataView {
                 .into());
         }
 
+        // 2. Perform ? RequireInternalSlot(buffer, [[ArrayBufferData]]).
+        let buffer_obj = args
+            .get_or_undefined(0)
+            .as_object()
+            .and_then(|o| o.clone().into_buffer_object().ok())
+            .ok_or_else(|| JsNativeError::typ().with_message("buffer must be an ArrayBuffer"))?;
+
         let (offset, view_byte_length) = {
-            // 2. Perform ? RequireInternalSlot(buffer, [[ArrayBufferData]]).
-            let buffer_borrow = buffer_obj.borrow();
-            let buffer = buffer_borrow.as_buffer().ok_or_else(|| {
-                JsNativeError::typ().with_message("buffer must be an ArrayBuffer")
-            })?;
+            let buffer = buffer_obj.as_buffer();
 
             // 3. Let offset be ? ToIndex(byteOffset).
             let offset = args.get_or_undefined(1).to_index(context)?;
+
             // 4. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
             let Some(buffer) = buffer.data() else {
                 return Err(JsNativeError::typ()
@@ -195,12 +197,7 @@ impl BuiltInConstructor for DataView {
             get_prototype_from_constructor(new_target, StandardConstructors::data_view, context)?;
 
         // 10. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
-        if buffer_obj
-            .borrow()
-            .as_buffer()
-            .expect("already checked that `buffer_obj` was a buffer")
-            .is_detached()
-        {
+        if buffer_obj.as_buffer().is_detached() {
             return Err(JsNativeError::typ()
                 .with_message("ArrayBuffer can't be detached")
                 .into());
@@ -211,7 +208,7 @@ impl BuiltInConstructor for DataView {
             prototype,
             Self {
                 // 11. Set O.[[ViewedArrayBuffer]] to buffer.
-                viewed_array_buffer: buffer_obj.clone(),
+                viewed_array_buffer: buffer_obj,
                 // 12. Set O.[[ByteLength]] to viewByteLength.
                 byte_length: view_byte_length,
                 // 13. Set O.[[ByteOffset]] to offset.
@@ -277,12 +274,9 @@ impl DataView {
             .ok_or_else(|| JsNativeError::typ().with_message("`this` is not a DataView"))?;
         // 3. Assert: O has a [[ViewedArrayBuffer]] internal slot.
         // 4. Let buffer be O.[[ViewedArrayBuffer]].
-        let buffer_borrow = view.viewed_array_buffer.borrow();
-        let borrow = buffer_borrow
-            .as_buffer()
-            .expect("DataView must be constructed with a Buffer");
+        let buffer = view.viewed_array_buffer.as_buffer();
         // 5. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
-        if borrow.is_detached() {
+        if buffer.is_detached() {
             return Err(JsNativeError::typ()
                 .with_message("ArrayBuffer is detached")
                 .into());
@@ -317,12 +311,9 @@ impl DataView {
             .ok_or_else(|| JsNativeError::typ().with_message("`this` is not a DataView"))?;
         // 3. Assert: O has a [[ViewedArrayBuffer]] internal slot.
         // 4. Let buffer be O.[[ViewedArrayBuffer]].
-        let buffer_borrow = view.viewed_array_buffer.borrow();
-        let borrow = buffer_borrow
-            .as_buffer()
-            .expect("DataView must be constructed with a Buffer");
+        let buffer = view.viewed_array_buffer.as_buffer();
         // 5. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
-        if borrow.is_detached() {
+        if buffer.is_detached() {
             return Err(JsNativeError::typ()
                 .with_message("Buffer is detached")
                 .into());
@@ -362,9 +353,7 @@ impl DataView {
         let is_little_endian = is_little_endian.to_boolean();
 
         // 5. Let buffer be view.[[ViewedArrayBuffer]].
-        let buffer = &view.viewed_array_buffer;
-        let buffer_borrow = buffer.borrow();
-        let buffer = buffer_borrow.as_buffer().expect("Should be unreachable");
+        let buffer = view.viewed_array_buffer.as_buffer();
 
         // 6. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
         let Some(data) = buffer.data() else {
@@ -676,11 +665,7 @@ impl DataView {
         // 6. Set isLittleEndian to ! ToBoolean(isLittleEndian).
         let is_little_endian = is_little_endian.to_boolean();
         // 7. Let buffer be view.[[ViewedArrayBuffer]].
-        let buffer = &view.viewed_array_buffer;
-        let mut buffer_borrow = buffer.borrow_mut();
-        let mut buffer = buffer_borrow
-            .as_buffer_mut()
-            .expect("Should be unreachable");
+        let mut buffer = view.viewed_array_buffer.as_buffer_mut();
 
         // 8. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
         let Some(mut data) = buffer.data_mut() else {

core/engine/src/builtins/typed_array/builtin.rs

@@ -1,14 +1,17 @@
-use std::{cmp, ptr, sync::atomic};
+use std::{cmp, sync::atomic};
 
 use boa_macros::utf16;
 use num_traits::Zero;
 
+use super::{
+    object::typed_array_set_element, ContentType, TypedArray, TypedArrayKind, TypedArrayMarker,
+};
 use crate::{
     builtins::{
         array::{find_via_predicate, ArrayIterator, Direction},
         array_buffer::{
             utils::{memcpy, memmove, SliceRefMut},
-            ArrayBuffer, BufferRef,
+            ArrayBuffer, BufferObject,
         },
         iterable::iterable_to_list,
         Array, BuiltInBuilder, BuiltInConstructor, BuiltInObject, IntrinsicObject,
@@ -23,11 +26,6 @@ use crate::{
     Context, JsArgs, JsNativeError, JsObject, JsResult, JsString, JsSymbol, JsValue,
 };
 
-use super::{
-    integer_indexed_object::integer_indexed_element_set, ContentType, TypedArray, TypedArrayKind,
-    TypedArrayMarker,
-};
-
 /// The JavaScript `%TypedArray%` object.
 ///
 /// <https://tc39.es/ecma262/#sec-%typedarray%-intrinsic-object>
@@ -427,7 +425,7 @@ impl BuiltinTypedArray {
 
         // 4. Let buffer be O.[[ViewedArrayBuffer]].
         // 5. Return buffer.
-        Ok(typed_array.viewed_array_buffer().clone().into())
+        Ok(JsObject::from(typed_array.viewed_array_buffer().clone()).into())
     }
 
     /// `23.2.3.3 get %TypedArray%.prototype.byteLength`
@@ -574,10 +572,7 @@ impl BuiltinTypedArray {
             // b. Let buffer be O.[[ViewedArrayBuffer]].
             // c. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
             let buffer_obj = o.viewed_array_buffer();
-            let mut buffer_obj_borrow = buffer_obj.borrow_mut();
-            let mut buffer = buffer_obj_borrow
-                .as_buffer_mut()
-                .expect("Already checked for detached buffer");
+            let mut buffer = buffer_obj.as_buffer_mut();
             let Some(buffer) = buffer.data_mut() else {
                 return Err(JsNativeError::typ()
                     .with_message("Buffer of the typed array is detached")
@@ -2060,34 +2055,14 @@ impl BuiltinTypedArray {
         // 18. If IsSharedArrayBuffer(srcBuffer) is true, IsSharedArrayBuffer(targetBuffer) is true,
         //     and srcBuffer.[[ArrayBufferData]] is targetBuffer.[[ArrayBufferData]], let
         //     sameSharedArrayBuffer be true; otherwise, let sameSharedArrayBuffer be false.
-        let same = if JsObject::equals(&src_buffer_obj, &target_buffer_obj) {
-            true
-        } else {
-            let src_buffer_obj = src_buffer_obj.borrow();
-            let src_buffer = src_buffer_obj.as_buffer().expect("Must be an array buffer");
-
-            let target_buffer_obj = target_buffer_obj.borrow();
-            let target_buffer = target_buffer_obj
-                .as_buffer()
-                .expect("Must be an array buffer");
-
-            match (src_buffer, target_buffer) {
-                (BufferRef::SharedBuffer(src), BufferRef::SharedBuffer(dest)) => {
-                    ptr::eq(src.data(), dest.data())
-                }
-                (_, _) => false,
-            }
-        };
-
         // 19. If SameValue(srcBuffer, targetBuffer) is true or sameSharedArrayBuffer is true, then
-        let src_byte_index = if same {
+        let src_byte_index = if BufferObject::equals(&src_buffer_obj, &target_buffer_obj) {
             // a. Let srcByteLength be source.[[ByteLength]].
             let src_byte_offset = src_byte_offset as usize;
             let src_byte_length = source_array.byte_length() as usize;
 
             let s = {
-                let slice = src_buffer_obj.borrow();
-                let slice = slice.as_buffer().expect("Must be an array buffer");
+                let slice = src_buffer_obj.as_buffer();
                 let slice = slice.data().expect("Already checked for detached buffer");
 
                 // b. Set srcBuffer to ? CloneArrayBuffer(srcBuffer, srcByteOffset, srcByteLength, %ArrayBuffer%).
@@ -2096,8 +2071,7 @@ impl BuiltinTypedArray {
                     .subslice(src_byte_offset..src_byte_offset + src_byte_length)
                     .clone(context)?
             };
-            // TODO: skip this upcast
-            src_buffer_obj = s.upcast();
+            src_buffer_obj = BufferObject::Buffer(s);
 
             // d. Let srcByteIndex be 0.
             0
@@ -2112,16 +2086,12 @@ impl BuiltinTypedArray {
         // 22. Let targetByteIndex be targetOffset × targetElementSize + targetByteOffset.
         let target_byte_index = target_offset * target_element_size + target_byte_offset;
 
-        let src_buffer = src_buffer_obj.borrow();
-        let src_buffer = src_buffer.as_buffer().expect("Must be an array buffer");
+        let src_buffer = src_buffer_obj.as_buffer();
         let src_buffer = src_buffer
             .data()
             .expect("Already checked for detached buffer");
 
-        let mut target_buffer = target_buffer_obj.borrow_mut();
-        let mut target_buffer = target_buffer
-            .as_buffer_mut()
-            .expect("Must be an array buffer");
+        let mut target_buffer = target_buffer_obj.as_buffer_mut();
         let mut target_buffer = target_buffer
             .data_mut()
             .expect("Already checked for detached buffer");
@@ -2255,7 +2225,7 @@ impl BuiltinTypedArray {
             let target_index = target_offset + k;
 
             // d. Perform ? IntegerIndexedElementSet(target, targetIndex, value).
-            integer_indexed_element_set(target, target_index as f64, &value, &mut context.into())?;
+            typed_array_set_element(target, target_index as f64, &value, &mut context.into())?;
 
             // e. Set k to k + 1.
         }
@@ -2377,18 +2347,12 @@ impl BuiltinTypedArray {
             } else {
                 // i. Let srcBuffer be O.[[ViewedArrayBuffer]].
                 let src_buffer_obj = o.viewed_array_buffer();
-                let src_buffer_obj_borrow = src_buffer_obj.borrow();
-                let src_buffer = src_buffer_obj_borrow
-                    .as_buffer()
-                    .expect("view must be a buffer");
+                let src_buffer = src_buffer_obj.as_buffer();
                 let src_buffer = src_buffer.data().expect("cannot be detached here");
 
                 // ii. Let targetBuffer be A.[[ViewedArrayBuffer]].
                 let target_buffer_obj = a_array.viewed_array_buffer();
-                let mut target_buffer_obj_borrow = target_buffer_obj.borrow_mut();
-                let mut target_buffer = target_buffer_obj_borrow
-                    .as_buffer_mut()
-                    .expect("view must be a buffer");
+                let mut target_buffer = target_buffer_obj.as_buffer_mut();
                 let mut target_buffer = target_buffer.data_mut().expect("cannot be detached here");
 
                 // iii. Let elementSize be the Element Size value specified in Table 73 for Element Type srcType.
@@ -2713,7 +2677,7 @@ impl BuiltinTypedArray {
             obj,
             o.kind(),
             &[
-                buffer.clone().into(),
+                JsObject::from(buffer.clone()).into(),
                 begin_byte_offset.into(),
                 new_length.into(),
             ],
@@ -3069,9 +3033,8 @@ impl BuiltinTypedArray {
         // 9. Set O.[[ArrayLength]] to length.
 
         // 10. Return O.
-        // TODO: skip this upcast.
         Ok(TypedArray::new(
-            data.upcast(),
+            BufferObject::Buffer(data),
             T::ERASED,
             0,
             byte_length,
@@ -3153,18 +3116,14 @@ impl BuiltinTypedArray {
     /// [spec]: https://tc39.es/ecma262/#sec-initializetypedarrayfromtypedarray
     pub(super) fn initialize_from_typed_array<T: TypedArrayMarker>(
         proto: JsObject,
-        src_array: &JsObject,
+        src_array: &JsObject<TypedArray>,
         context: &mut Context,
     ) -> JsResult<JsObject> {
         let src_array = src_array.borrow();
-        let src_array = src_array
-            .downcast_ref::<TypedArray>()
-            .expect("this must be a typed array");
+        let src_array = &src_array.data;
+
         let src_data = src_array.viewed_array_buffer();
-        let src_data = src_data.borrow();
-        let src_data = src_data
-            .as_buffer()
-            .expect("integer indexed must have a buffer");
+        let src_data = src_data.as_buffer();
 
         // 1. Let srcData be srcArray.[[ViewedArrayBuffer]].
         // 2. If IsDetachedBuffer(srcData) is true, throw a TypeError exception.
@@ -3288,12 +3247,11 @@ impl BuiltinTypedArray {
         // 13. Set O.[[ByteLength]] to byteLength.
         // 14. Set O.[[ByteOffset]] to 0.
         // 15. Set O.[[ArrayLength]] to elementLength.
-        // TODO: Skip this upcast.
         let obj = JsObject::from_proto_and_data_with_shared_shape(
             context.root_shape(),
             proto,
             TypedArray::new(
-                new_buffer.upcast(),
+                BufferObject::Buffer(new_buffer),
                 element_type,
                 0,
                 byte_length,
@@ -3313,7 +3271,7 @@ impl BuiltinTypedArray {
     /// [spec]: https://tc39.es/ecma262/#sec-initializetypedarrayfromarraybuffer
     pub(super) fn initialize_from_array_buffer<T: TypedArrayMarker>(
         proto: JsObject,
-        buffer: JsObject,
+        buffer: BufferObject,
         byte_offset: &JsValue,
         length: &JsValue,
         context: &mut Context,
@@ -3342,10 +3300,9 @@ impl BuiltinTypedArray {
         // 5. If IsDetachedBuffer(buffer) is true, throw a TypeError exception.
         // 6. Let bufferByteLength be buffer.[[ArrayBufferByteLength]].
         let buffer_byte_length = {
-            let buffer_borrow = buffer.borrow();
-            let buffer_array = buffer_borrow.as_buffer().expect("Must be a buffer");
+            let buffer = buffer.as_buffer();
 
-            let Some(data) = buffer_array.data() else {
+            let Some(data) = buffer.data() else {
                 return Err(JsNativeError::typ()
                     .with_message("Cannot construct typed array from detached buffer")
                     .into());

core/engine/src/builtins/typed_array/element/mod.rs

@@ -277,7 +277,8 @@ macro_rules! element {
             }
 
             unsafe fn read(buffer: SliceRef<'_>) -> ElementRef<'_, Self> {
-                if cfg!(debug_assertions) {
+                #[cfg(debug_assertions)]
+                {
                     assert!(buffer.len() >= std::mem::size_of::<Self>());
                     assert!(buffer.addr() % std::mem::align_of::<Self>() == 0);
                 }
@@ -293,7 +294,8 @@ macro_rules! element {
             }
 
             unsafe fn read_mut(buffer: SliceRefMut<'_>) -> ElementRefMut<'_, Self> {
-                if cfg!(debug_assertions) {
+                #[cfg(debug_assertions)]
+                {
                     assert!(buffer.len() >= std::mem::size_of::<Self>());
                     assert!(buffer.addr() % std::mem::align_of::<Self>() == 0);
                 }

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

@@ -28,15 +28,16 @@ use crate::{
     value::{JsValue, Numeric},
     Context, JsArgs, JsResult, JsString,
 };
+use boa_gc::{Finalize, Trace};
 use boa_profiler::Profiler;
 
 mod builtin;
 mod element;
-mod integer_indexed_object;
+mod object;
 
 pub(crate) use builtin::{is_valid_integer_index, BuiltinTypedArray};
 pub(crate) use element::{Atomic, ClampedU8, Element};
-pub use integer_indexed_object::{IntegerIndexed, TypedArray};
+pub use object::TypedArray;
 
 pub(crate) trait TypedArrayMarker {
     type Element: Element;
@@ -137,18 +138,39 @@ impl<T: TypedArrayMarker> BuiltInConstructor for T {
         let first_argument = &args[0];
 
         // b. If Type(firstArgument) is Object, then
-        if let Some(first_argument) = first_argument.as_object() {
-            // i. Let O be ? AllocateTypedArray(constructorName, NewTarget, proto).
-            let proto =
-                get_prototype_from_constructor(new_target, T::STANDARD_CONSTRUCTOR, context)?;
+        let Some(first_argument) = first_argument.as_object() else {
+            // c. Else,
+            // i. Assert: firstArgument is not an Object.
+            // Ensured by the let-else
+
+            // ii. Let elementLength be ? ToIndex(firstArgument).
+            let element_length = first_argument.to_index(context)?;
+
+            // iii. Return ? AllocateTypedArray(constructorName, NewTarget, proto, elementLength).
+            return BuiltinTypedArray::allocate::<T>(new_target, element_length, context)
+                .map(JsValue::from);
+        };
 
-            // ii. If firstArgument has a [[TypedArrayName]] internal slot, then
-            let o = if first_argument.is::<TypedArray>() {
+        let first_argument = first_argument.clone();
+
+        // i. Let O be ? AllocateTypedArray(constructorName, NewTarget, proto).
+        let proto = get_prototype_from_constructor(new_target, T::STANDARD_CONSTRUCTOR, context)?;
+
+        // ii. If firstArgument has a [[TypedArrayName]] internal slot, then
+        let first_argument = match first_argument.downcast::<TypedArray>() {
+            Ok(arr) => {
                 // 1. Perform ? InitializeTypedArrayFromTypedArray(O, firstArgument).
-                BuiltinTypedArray::initialize_from_typed_array::<T>(proto, first_argument, context)?
-            } else if first_argument.is_buffer() {
-                // iii. Else if firstArgument has an [[ArrayBufferData]] internal slot, then
 
+                // v. Return O.
+                return BuiltinTypedArray::initialize_from_typed_array::<T>(proto, &arr, context)
+                    .map(JsValue::from);
+            }
+            Err(obj) => obj,
+        };
+
+        // iii. Else if firstArgument has an [[ArrayBufferData]] internal slot, then
+        let first_argument = match first_argument.into_buffer_object() {
+            Ok(buf) => {
                 // 1. If numberOfArgs > 1, let byteOffset be args[1]; else let byteOffset be undefined.
                 let byte_offset = args.get_or_undefined(1);
 
@@ -156,59 +178,46 @@ impl<T: TypedArrayMarker> BuiltInConstructor for T {
                 let length = args.get_or_undefined(2);
 
                 // 3. Perform ? InitializeTypedArrayFromArrayBuffer(O, firstArgument, byteOffset, length).
-                BuiltinTypedArray::initialize_from_array_buffer::<T>(
+
+                // v. Return O.
+                return BuiltinTypedArray::initialize_from_array_buffer::<T>(
                     proto,
-                    first_argument.clone(),
+                    buf,
                     byte_offset,
                     length,
                     context,
-                )?
-            } else {
-                // iv. Else,
-
-                // 1. Assert: Type(firstArgument) is Object and firstArgument does not have
-                // either a [[TypedArrayName]] or an [[ArrayBufferData]] internal slot.
-
-                // 2. Let usingIterator be ? GetMethod(firstArgument, @@iterator).
-
-                let first_argument_v = JsValue::from(first_argument.clone());
-                let using_iterator = first_argument_v.get_method(JsSymbol::iterator(), context)?;
-
-                // 3. If usingIterator is not undefined, then
-                if let Some(using_iterator) = using_iterator {
-                    // a. Let values be ? IterableToList(firstArgument, usingIterator).
-                    let values =
-                        iterable_to_list(context, &first_argument_v, Some(using_iterator))?;
-
-                    // b. Perform ? InitializeTypedArrayFromList(O, values).
-                    BuiltinTypedArray::initialize_from_list::<T>(proto, values, context)?
-                } else {
-                    // 4. Else,
-
-                    // a. NOTE: firstArgument is not an Iterable so assume it is already an array-like object.
-                    // b. Perform ? InitializeTypedArrayFromArrayLike(O, firstArgument).
-                    BuiltinTypedArray::initialize_from_array_like::<T>(
-                        proto,
-                        first_argument,
-                        context,
-                    )?
-                }
-            };
-
-            // v. Return O.
-            Ok(o.into())
-        } else {
-            // c. Else,
+                )
+                .map(JsValue::from);
+            }
+            Err(obj) => obj,
+        };
 
-            // i. Assert: firstArgument is not an Object.
-            assert!(!first_argument.is_object(), "firstArgument was an object");
+        // iv. Else,
 
-            // ii. Let elementLength be ? ToIndex(firstArgument).
-            let element_length = first_argument.to_index(context)?;
+        // 1. Assert: Type(firstArgument) is Object and firstArgument does not have
+        // either a [[TypedArrayName]] or an [[ArrayBufferData]] internal slot.
 
-            // iii. Return ? AllocateTypedArray(constructorName, NewTarget, proto, elementLength).
-            Ok(BuiltinTypedArray::allocate::<T>(new_target, element_length, context)?.into())
+        // 2. Let usingIterator be ? GetMethod(firstArgument, @@iterator).
+
+        let using_iterator = first_argument.get_method(JsSymbol::iterator(), context)?;
+
+        // 3. If usingIterator is not undefined, then
+        if let Some(using_iterator) = using_iterator {
+            // a. Let values be ? IterableToList(firstArgument, usingIterator).
+            let values = iterable_to_list(context, &first_argument.into(), Some(using_iterator))?;
+
+            // b. Perform ? InitializeTypedArrayFromList(O, values).
+            BuiltinTypedArray::initialize_from_list::<T>(proto, values, context)
+        } else {
+            // 4. Else,
+
+            // a. NOTE: firstArgument is not an Iterable so assume it is already an array-like object.
+            // b. Perform ? InitializeTypedArrayFromArrayLike(O, firstArgument).
+            BuiltinTypedArray::initialize_from_array_like::<T>(proto, &first_argument, context)
         }
+        .map(JsValue::from)
+
+        // v. Return O.
     }
 }
 
@@ -330,7 +339,8 @@ pub(crate) enum ContentType {
 }
 
 /// List of all typed array kinds.
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Trace, Finalize)]
+#[boa_gc(empty_trace)]
 pub(crate) enum TypedArrayKind {
     Int8,
     Uint8,

core/engine/src/builtins/typed_array/object.rs

@@ -1,9 +1,9 @@
-//! This module implements the `Integer-Indexed` exotic object.
+//! This module implements the `TypedArray` exotic object.
 
 use std::sync::atomic;
 
 use crate::{
-    builtins::Number,
+    builtins::{array_buffer::BufferObject, Number},
     object::{
         internal_methods::{
             ordinary_define_own_property, ordinary_delete, ordinary_get, ordinary_get_own_property,
@@ -20,22 +20,16 @@ use boa_macros::utf16;
 
 use super::{is_valid_integer_index, TypedArrayKind};
 
-/// An `IntegerIndexed` object is just an alias for a `TypedArray` object.
-pub type IntegerIndexed = TypedArray;
-
-/// A `TypedArrayObject` is an exotic object that performs special handling of integer
+/// A `TypedArray` object is an exotic object that performs special handling of integer
 /// index property keys.
 ///
-/// This is also called an `IntegerIndexed` object in the specification.
-///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-exotic-objects
 #[derive(Debug, Clone, Trace, Finalize)]
 pub struct TypedArray {
-    viewed_array_buffer: JsObject,
-    #[unsafe_ignore_trace]
+    viewed_array_buffer: BufferObject,
     kind: TypedArrayKind,
     byte_offset: u64,
     byte_length: u64,
@@ -45,13 +39,13 @@ pub struct TypedArray {
 impl JsData for TypedArray {
     fn internal_methods(&self) -> &'static InternalObjectMethods {
         static METHODS: InternalObjectMethods = InternalObjectMethods {
-            __get_own_property__: integer_indexed_exotic_get_own_property,
-            __has_property__: integer_indexed_exotic_has_property,
-            __define_own_property__: integer_indexed_exotic_define_own_property,
-            __get__: integer_indexed_exotic_get,
-            __set__: integer_indexed_exotic_set,
-            __delete__: integer_indexed_exotic_delete,
-            __own_property_keys__: integer_indexed_exotic_own_property_keys,
+            __get_own_property__: typed_array_exotic_get_own_property,
+            __has_property__: typed_array_exotic_has_property,
+            __define_own_property__: typed_array_exotic_define_own_property,
+            __get__: typed_array_exotic_get,
+            __set__: typed_array_exotic_set,
+            __delete__: typed_array_exotic_delete,
+            __own_property_keys__: typed_array_exotic_own_property_keys,
             ..ORDINARY_INTERNAL_METHODS
         };
 
@@ -61,7 +55,7 @@ impl JsData for TypedArray {
 
 impl TypedArray {
     pub(crate) const fn new(
-        viewed_array_buffer: JsObject,
+        viewed_array_buffer: BufferObject,
         kind: TypedArrayKind,
         byte_offset: u64,
         byte_length: u64,
@@ -85,37 +79,33 @@ impl TypedArray {
     ///
     /// [spec]: https://tc39.es/ecma262/#sec-isdetachedbuffer
     pub(crate) fn is_detached(&self) -> bool {
-        self.viewed_array_buffer
-            .borrow()
-            .as_buffer()
-            .expect("Typed array must have internal array buffer object")
-            .is_detached()
+        self.viewed_array_buffer.as_buffer().is_detached()
     }
 
-    /// Get the integer indexed object's byte offset.
+    /// Get the `TypedArray` object's byte offset.
     #[must_use]
     pub const fn byte_offset(&self) -> u64 {
         self.byte_offset
     }
 
-    /// Get the integer indexed object's typed array kind.
+    /// Get the `TypedArray` object's typed array kind.
     pub(crate) const fn kind(&self) -> TypedArrayKind {
         self.kind
     }
 
-    /// Get a reference to the integer indexed object's viewed array buffer.
+    /// Get a reference to the `TypedArray` object's viewed array buffer.
     #[must_use]
-    pub const fn viewed_array_buffer(&self) -> &JsObject {
+    pub(crate) const fn viewed_array_buffer(&self) -> &BufferObject {
         &self.viewed_array_buffer
     }
 
-    /// Get the integer indexed object's byte length.
+    /// Get the `TypedArray` object's byte length.
     #[must_use]
     pub const fn byte_length(&self) -> u64 {
         self.byte_length
     }
 
-    /// Get the integer indexed object's array length.
+    /// Get the `TypedArray` object's array length.
     #[must_use]
     pub const fn array_length(&self) -> u64 {
         self.array_length
@@ -146,13 +136,13 @@ fn canonical_numeric_index_string(argument: &JsString) -> Option<f64> {
     None
 }
 
-/// `[[GetOwnProperty]]` internal method for Integer-Indexed exotic objects.
+/// `[[GetOwnProperty]]` internal method for `TypedArray` exotic objects.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects-getownproperty-p
-pub(crate) fn integer_indexed_exotic_get_own_property(
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-getownproperty
+pub(crate) fn typed_array_exotic_get_own_property(
     obj: &JsObject,
     key: &PropertyKey,
     context: &mut InternalMethodContext<'_>,
@@ -170,7 +160,7 @@ pub(crate) fn integer_indexed_exotic_get_own_property(
     // 1.b. If numericIndex is not undefined, then
     if let Some(numeric_index) = p {
         // i. Let value be IntegerIndexedElementGet(O, numericIndex).
-        let value = integer_indexed_element_get(obj, numeric_index);
+        let value = typed_array_get_element(obj, numeric_index);
 
         // ii. If value is undefined, return undefined.
         // iii. Return the PropertyDescriptor { [[Value]]: value, [[Writable]]: true, [[Enumerable]]: true, [[Configurable]]: true }.
@@ -188,13 +178,13 @@ pub(crate) fn integer_indexed_exotic_get_own_property(
     ordinary_get_own_property(obj, key, context)
 }
 
-/// `[[HasProperty]]` internal method for Integer-Indexed exotic objects.
+/// `[[HasProperty]]` internal method for `TypedArray` exotic objects.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects-hasproperty-p
-pub(crate) fn integer_indexed_exotic_has_property(
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-hasproperty
+pub(crate) fn typed_array_exotic_has_property(
     obj: &JsObject,
     key: &PropertyKey,
     context: &mut InternalMethodContext<'_>,
@@ -218,13 +208,13 @@ pub(crate) fn integer_indexed_exotic_has_property(
     ordinary_has_property(obj, key, context)
 }
 
-/// `[[DefineOwnProperty]]` internal method for Integer-Indexed exotic objects.
+/// `[[DefineOwnProperty]]` internal method for `TypedArray` exotic objects.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects-defineownproperty-p-desc
-pub(crate) fn integer_indexed_exotic_define_own_property(
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-defineownproperty
+pub(crate) fn typed_array_exotic_define_own_property(
     obj: &JsObject,
     key: &PropertyKey,
     desc: PropertyDescriptor,
@@ -269,7 +259,7 @@ pub(crate) fn integer_indexed_exotic_define_own_property(
 
         // vi. If Desc has a [[Value]] field, perform ? IntegerIndexedElementSet(O, numericIndex, Desc.[[Value]]).
         if let Some(value) = desc.value() {
-            integer_indexed_element_set(obj, numeric_index, value, context)?;
+            typed_array_set_element(obj, numeric_index, value, context)?;
         }
 
         // vii. Return true.
@@ -280,13 +270,13 @@ pub(crate) fn integer_indexed_exotic_define_own_property(
     ordinary_define_own_property(obj, key, desc, context)
 }
 
-/// Internal method `[[Get]]` for Integer-Indexed exotic objects.
+/// Internal method `[[Get]]` for `TypedArray` exotic objects.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects-get-p-receiver
-pub(crate) fn integer_indexed_exotic_get(
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-get
+pub(crate) fn typed_array_exotic_get(
     obj: &JsObject,
     key: &PropertyKey,
     receiver: JsValue,
@@ -305,20 +295,20 @@ pub(crate) fn integer_indexed_exotic_get(
     // 1.b. If numericIndex is not undefined, then
     if let Some(numeric_index) = p {
         // i. Return IntegerIndexedElementGet(O, numericIndex).
-        return Ok(integer_indexed_element_get(obj, numeric_index).unwrap_or_default());
+        return Ok(typed_array_get_element(obj, numeric_index).unwrap_or_default());
     }
 
     // 2. Return ? OrdinaryGet(O, P, Receiver).
     ordinary_get(obj, key, receiver, context)
 }
 
-/// Internal method `[[Set]]` for Integer-Indexed exotic objects.
+/// Internal method `[[Set]]` for `TypedArray` exotic objects.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects-set-p-v-receiver
-pub(crate) fn integer_indexed_exotic_set(
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-set
+pub(crate) fn typed_array_exotic_set(
     obj: &JsObject,
     key: PropertyKey,
     value: JsValue,
@@ -340,7 +330,7 @@ pub(crate) fn integer_indexed_exotic_set(
         // i. If SameValue(O, Receiver) is true, then
         if JsValue::same_value(&obj.clone().into(), &receiver) {
             // 1. Perform ? IntegerIndexedElementSet(O, numericIndex, V).
-            integer_indexed_element_set(obj, numeric_index, &value, context)?;
+            typed_array_set_element(obj, numeric_index, &value, context)?;
 
             // 2. Return true.
             return Ok(true);
@@ -356,13 +346,13 @@ pub(crate) fn integer_indexed_exotic_set(
     ordinary_set(obj, key, value, receiver, context)
 }
 
-/// Internal method `[[Delete]]` for Integer-Indexed exotic objects.
+/// Internal method `[[Delete]]` for `TypedArray` exotic objects.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects-delete-p
-pub(crate) fn integer_indexed_exotic_delete(
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-delete
+pub(crate) fn typed_array_exotic_delete(
     obj: &JsObject,
     key: &PropertyKey,
     context: &mut InternalMethodContext<'_>,
@@ -387,21 +377,21 @@ pub(crate) fn integer_indexed_exotic_delete(
     ordinary_delete(obj, key, context)
 }
 
-/// Internal method `[[OwnPropertyKeys]]` for Integer-Indexed exotic objects.
+/// Internal method `[[OwnPropertyKeys]]` for `TypedArray` exotic objects.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integer-indexed-exotic-objects-ownpropertykeys
+/// [spec]: https://tc39.es/ecma262/#sec-typedarray-ownpropertykeys
 #[allow(clippy::unnecessary_wraps)]
-pub(crate) fn integer_indexed_exotic_own_property_keys(
+pub(crate) fn typed_array_exotic_own_property_keys(
     obj: &JsObject,
     _context: &mut Context,
 ) -> JsResult<Vec<PropertyKey>> {
     let obj = obj.borrow();
-    let inner = obj.downcast_ref::<TypedArray>().expect(
-        "integer indexed exotic method should only be callable from integer indexed objects",
-    );
+    let inner = obj
+        .downcast_ref::<TypedArray>()
+        .expect("TypedArray exotic method should only be callable from TypedArray objects");
 
     // 1. Let keys be a new empty List.
     let mut keys = if inner.is_detached() {
@@ -424,13 +414,13 @@ pub(crate) fn integer_indexed_exotic_own_property_keys(
     Ok(keys)
 }
 
-/// Abstract operation `IntegerIndexedElementGet ( O, index )`.
+/// Abstract operation `TypedArrayGetElement ( O, index )`.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integerindexedelementget
-fn integer_indexed_element_get(obj: &JsObject, index: f64) -> Option<JsValue> {
+/// [spec]: https://tc39.es/ecma262/sec-typedarraygetelement
+fn typed_array_get_element(obj: &JsObject, index: f64) -> Option<JsValue> {
     // 1. If ! IsValidIntegerIndex(O, index) is false, return undefined.
     if !is_valid_integer_index(obj, index) {
         return None;
@@ -438,10 +428,9 @@ fn integer_indexed_element_get(obj: &JsObject, index: f64) -> Option<JsValue> {
 
     let inner = obj
         .downcast_ref::<TypedArray>()
-        .expect("Must be an integer indexed object");
+        .expect("Must be an TypedArray object");
     let buffer = inner.viewed_array_buffer();
-    let buffer = buffer.borrow();
-    let buffer = buffer.as_buffer().expect("Must be a buffer");
+    let buffer = buffer.as_buffer();
     let buffer = buffer
         .data()
         .expect("already checked that it's not detached");
@@ -461,7 +450,7 @@ fn integer_indexed_element_get(obj: &JsObject, index: f64) -> Option<JsValue> {
 
     // 7. Return GetValueFromBuffer(O.[[ViewedArrayBuffer]], indexedPosition, elementType, true, Unordered).
 
-    // SAFETY: The integer indexed object guarantees that the buffer is aligned.
+    // SAFETY: The TypedArray object guarantees that the buffer is aligned.
     // The call to `is_valid_integer_index` guarantees that the index is in-bounds.
     let value = unsafe {
         buffer
@@ -472,22 +461,22 @@ fn integer_indexed_element_get(obj: &JsObject, index: f64) -> Option<JsValue> {
     Some(value.into())
 }
 
-/// Abstract operation `IntegerIndexedElementSet ( O, index, value )`.
+/// Abstract operation `TypedArraySetElement ( O, index, value )`.
 ///
 /// More information:
 ///  - [ECMAScript reference][spec]
 ///
-/// [spec]: https://tc39.es/ecma262/#sec-integerindexedelementset
-pub(crate) fn integer_indexed_element_set(
+/// [spec]: https://tc39.es/ecma262/#sec-typedarraysetelement
+pub(crate) fn typed_array_set_element(
     obj: &JsObject,
     index: f64,
     value: &JsValue,
     context: &mut InternalMethodContext<'_>,
 ) -> JsResult<()> {
     let obj_borrow = obj.borrow();
-    let inner = obj_borrow.downcast_ref::<TypedArray>().expect(
-        "integer indexed exotic method should only be callable from integer indexed objects",
-    );
+    let inner = obj_borrow
+        .downcast_ref::<TypedArray>()
+        .expect("TypedArray exotic method should only be callable from TypedArray objects");
 
     // 1. If O.[[ContentType]] is BigInt, let numValue be ? ToBigInt(value).
     // 2. Otherwise, let numValue be ? ToNumber(value).
@@ -512,15 +501,14 @@ pub(crate) fn integer_indexed_element_set(
     let indexed_position = ((index as u64 * size) + offset) as usize;
 
     let buffer = inner.viewed_array_buffer();
-    let mut buffer = buffer.borrow_mut();
-    let mut buffer = buffer.as_buffer_mut().expect("Must be a buffer");
+    let mut buffer = buffer.as_buffer_mut();
     let mut buffer = buffer
         .data_mut()
         .expect("already checked that it's not detached");
 
     // f. Perform SetValueInBuffer(O.[[ViewedArrayBuffer]], indexedPosition, elementType, numValue, true, Unordered).
 
-    // SAFETY: The integer indexed object guarantees that the buffer is aligned.
+    // SAFETY: The TypedArray object guarantees that the buffer is aligned.
     // The call to `is_valid_integer_index` guarantees that the index is in-bounds.
     unsafe {
         buffer

core/engine/src/object/builtins/jsarraybuffer.rs

@@ -17,6 +17,20 @@ pub struct JsArrayBuffer {
     inner: JsObject<ArrayBuffer>,
 }
 
+impl From<JsArrayBuffer> for JsObject<ArrayBuffer> {
+    #[inline]
+    fn from(value: JsArrayBuffer) -> Self {
+        value.inner
+    }
+}
+
+impl From<JsObject<ArrayBuffer>> for JsArrayBuffer {
+    #[inline]
+    fn from(value: JsObject<ArrayBuffer>) -> Self {
+        Self { inner: value }
+    }
+}
+
 // TODO: Add constructors that also take the `detach_key` as argument.
 impl JsArrayBuffer {
     /// Create a new array buffer with byte length.
@@ -157,7 +171,7 @@ impl JsArrayBuffer {
     ///
     /// # Note
     ///
-    /// This tries to detach the pre-existing `JsArrayBuffer`, meaning the original detached
+    /// This tries to detach the pre-existing `JsArrayBuffer`, meaning the original detach
     /// key is required. By default, the key is set to `undefined`.
     ///
     /// ```

core/engine/src/object/builtins/jsdataview.rs

@@ -1,6 +1,6 @@
 //! A Rust API wrapper for Boa's `DataView` Builtin ECMAScript Object
 use crate::{
-    builtins::DataView,
+    builtins::{array_buffer::BufferObject, DataView},
     context::intrinsics::StandardConstructors,
     object::{
         internal_methods::get_prototype_from_constructor, JsArrayBuffer, JsObject, JsObjectType,
@@ -33,8 +33,23 @@ use std::ops::Deref;
 /// # }
 /// ```
 #[derive(Debug, Clone, Trace, Finalize)]
+#[boa_gc(unsafe_no_drop)]
 pub struct JsDataView {
-    inner: JsObject,
+    inner: JsObject<DataView>,
+}
+
+impl From<JsDataView> for JsObject<DataView> {
+    #[inline]
+    fn from(value: JsDataView) -> Self {
+        value.inner
+    }
+}
+
+impl From<JsObject<DataView>> for JsDataView {
+    #[inline]
+    fn from(value: JsObject<DataView>) -> Self {
+        Self { inner: value }
+    }
 }
 
 impl JsDataView {
@@ -90,12 +105,11 @@ impl JsDataView {
         let prototype =
             get_prototype_from_constructor(&constructor, StandardConstructors::data_view, context)?;
 
-        let obj = JsObject::from_proto_and_data_with_shared_shape(
+        let obj = JsObject::new(
             context.root_shape(),
             prototype,
             DataView {
-                // TODO: Remove upcast.
-                viewed_array_buffer: array_buffer.into(),
+                viewed_array_buffer: BufferObject::Buffer(array_buffer.into()),
                 byte_length,
                 byte_offset,
             },
@@ -107,32 +121,33 @@ impl JsDataView {
     /// Create a new `JsDataView` object from an existing object.
     #[inline]
     pub fn from_object(object: JsObject) -> JsResult<Self> {
-        if object.is::<DataView>() {
-            Ok(Self { inner: object })
-        } else {
-            Err(JsNativeError::typ()
-                .with_message("object is not a DataView")
-                .into())
-        }
+        object
+            .downcast::<DataView>()
+            .map(|inner| Self { inner })
+            .map_err(|_| {
+                JsNativeError::typ()
+                    .with_message("object is not a DataView")
+                    .into()
+            })
     }
 
     /// Returns the `viewed_array_buffer` field for [`JsDataView`]
     #[inline]
     pub fn buffer(&self, context: &mut Context) -> JsResult<JsValue> {
-        DataView::get_buffer(&self.inner.clone().into(), &[], context)
+        DataView::get_buffer(&self.inner.clone().upcast().into(), &[], context)
     }
 
     /// Returns the `byte_length` property of [`JsDataView`] as a u64 integer
     #[inline]
     pub fn byte_length(&self, context: &mut Context) -> JsResult<u64> {
-        DataView::get_byte_length(&self.inner.clone().into(), &[], context)
+        DataView::get_byte_length(&self.inner.clone().upcast().into(), &[], context)
             .map(|v| v.as_number().expect("value should be a number") as u64)
     }
 
     /// Returns the `byte_offset` field property of [`JsDataView`] as a u64 integer
     #[inline]
     pub fn byte_offset(&self, context: &mut Context) -> JsResult<u64> {
-        DataView::get_byte_offset(&self.inner.clone().into(), &[], context)
+        DataView::get_byte_offset(&self.inner.clone().upcast().into(), &[], context)
             .map(|v| v.as_number().expect("byte_offset value must be a number") as u64)
     }
 
@@ -145,7 +160,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<i64> {
         DataView::get_big_int64(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -161,7 +176,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<u64> {
         DataView::get_big_uint64(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -177,7 +192,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<f32> {
         DataView::get_float32(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -193,7 +208,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<f64> {
         DataView::get_float64(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -209,7 +224,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<i8> {
         DataView::get_int8(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -225,7 +240,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<i16> {
         DataView::get_int16(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -241,7 +256,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<i32> {
         DataView::get_int32(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -257,7 +272,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<u8> {
         DataView::get_uint8(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -273,7 +288,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<u16> {
         DataView::get_uint16(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -289,7 +304,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<u32> {
         DataView::get_uint32(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), is_little_endian.into()],
             context,
         )
@@ -306,7 +321,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_big_int64(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -322,7 +337,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_big_uint64(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -338,7 +353,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_float32(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -354,7 +369,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_float64(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -370,7 +385,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_int8(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -386,7 +401,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_int16(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -402,7 +417,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_int32(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -418,7 +433,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_uint8(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -434,7 +449,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_uint16(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -450,7 +465,7 @@ impl JsDataView {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         DataView::set_uint32(
-            &self.inner.clone().into(),
+            &self.inner.clone().upcast().into(),
             &[byte_offset.into(), value.into(), is_little_endian.into()],
             context,
         )
@@ -460,19 +475,19 @@ impl JsDataView {
 impl From<JsDataView> for JsObject {
     #[inline]
     fn from(o: JsDataView) -> Self {
-        o.inner.clone()
+        o.inner.upcast()
     }
 }
 
 impl From<JsDataView> for JsValue {
     #[inline]
     fn from(o: JsDataView) -> Self {
-        o.inner.clone().into()
+        o.inner.upcast().into()
     }
 }
 
 impl Deref for JsDataView {
-    type Target = JsObject;
+    type Target = JsObject<DataView>;
 
     #[inline]
     fn deref(&self) -> &Self::Target {

core/engine/src/object/builtins/jssharedarraybuffer.rs

@@ -11,8 +11,23 @@ use std::ops::Deref;
 
 /// `JsSharedArrayBuffer` provides a wrapper for Boa's implementation of the ECMAScript `ArrayBuffer` object
 #[derive(Debug, Clone, Trace, Finalize)]
+#[boa_gc(unsafe_no_drop)]
 pub struct JsSharedArrayBuffer {
-    inner: JsObject,
+    inner: JsObject<SharedArrayBuffer>,
+}
+
+impl From<JsSharedArrayBuffer> for JsObject<SharedArrayBuffer> {
+    #[inline]
+    fn from(value: JsSharedArrayBuffer) -> Self {
+        value.inner
+    }
+}
+
+impl From<JsObject<SharedArrayBuffer>> for JsSharedArrayBuffer {
+    #[inline]
+    fn from(value: JsObject<SharedArrayBuffer>) -> Self {
+        JsSharedArrayBuffer { inner: value }
+    }
 }
 
 impl JsSharedArrayBuffer {
@@ -42,8 +57,7 @@ impl JsSharedArrayBuffer {
             .shared_array_buffer()
             .prototype();
 
-        let inner =
-            JsObject::from_proto_and_data_with_shared_shape(context.root_shape(), proto, buffer);
+        let inner = JsObject::new(context.root_shape(), proto, buffer);
 
         Self { inner }
     }
@@ -55,50 +69,47 @@ impl JsSharedArrayBuffer {
     /// the object.
     #[inline]
     pub fn from_object(object: JsObject) -> JsResult<Self> {
-        if object.is::<SharedArrayBuffer>() {
-            Ok(Self { inner: object })
-        } else {
-            Err(JsNativeError::typ()
-                .with_message("object is not an ArrayBuffer")
-                .into())
-        }
+        object
+            .downcast::<SharedArrayBuffer>()
+            .map(|inner| Self { inner })
+            .map_err(|_| {
+                JsNativeError::typ()
+                    .with_message("object is not a SharedArrayBuffer")
+                    .into()
+            })
     }
 
     /// Returns the byte length of the array buffer.
     #[inline]
     #[must_use]
     pub fn byte_length(&self) -> usize {
-        self.downcast_ref::<SharedArrayBuffer>()
-            .expect("should be an array buffer")
-            .len()
+        self.borrow().data.len()
     }
 
     /// Gets the raw buffer of this `JsSharedArrayBuffer`.
     #[inline]
     #[must_use]
     pub fn inner(&self) -> SharedArrayBuffer {
-        self.downcast_ref::<SharedArrayBuffer>()
-            .expect("should be an array buffer")
-            .clone()
+        self.borrow().data.clone()
     }
 }
 
 impl From<JsSharedArrayBuffer> for JsObject {
     #[inline]
     fn from(o: JsSharedArrayBuffer) -> Self {
-        o.inner.clone()
+        o.inner.upcast()
     }
 }
 
 impl From<JsSharedArrayBuffer> for JsValue {
     #[inline]
     fn from(o: JsSharedArrayBuffer) -> Self {
-        o.inner.clone().into()
+        o.inner.upcast().into()
     }
 }
 
 impl Deref for JsSharedArrayBuffer {
-    type Target = JsObject;
+    type Target = JsObject<SharedArrayBuffer>;
 
     #[inline]
     fn deref(&self) -> &Self::Target {

core/engine/src/object/jsobject.rs

@@ -8,7 +8,11 @@ use super::{
     JsPrototype, NativeObject, Object, PrivateName, PropertyMap,
 };
 use crate::{
-    builtins::{array::ARRAY_EXOTIC_INTERNAL_METHODS, object::OrdinaryObject},
+    builtins::{
+        array::ARRAY_EXOTIC_INTERNAL_METHODS,
+        array_buffer::{ArrayBuffer, BufferObject, SharedArrayBuffer},
+        object::OrdinaryObject,
+    },
     context::intrinsics::Intrinsics,
     error::JsNativeError,
     js_string,
@@ -212,6 +216,24 @@ impl JsObject {
         }
     }
 
+    /// Downcasts the object's inner data to `T` without verifying the inner type of `T`.
+    ///
+    /// # Safety
+    ///
+    /// For this cast to be sound, `self` must contain an instance of `T` inside its inner data.
+    #[must_use]
+    pub unsafe fn downcast_unchecked<T: NativeObject>(self) -> JsObject<T> {
+        let ptr: NonNull<GcBox<VTableObject<T>>> = Gc::into_raw(self.inner).cast();
+
+        // SAFETY: The caller guarantees `T` is the original inner data type of the underlying
+        // object.
+        unsafe {
+            JsObject {
+                inner: Gc::from_raw(ptr),
+            }
+        }
+    }
+
     /// Downcasts a reference to the object,
     /// if the object is of type `T`.
     ///
@@ -268,18 +290,6 @@ impl JsObject {
         std::ptr::eq(self.vtable(), &ARRAY_EXOTIC_INTERNAL_METHODS)
     }
 
-    /// Checks if it's an `ArrayBuffer` or `SharedArrayBuffer` object.
-    ///
-    /// # Panics
-    ///
-    /// Panics if the object is currently mutably borrowed.
-    #[inline]
-    #[must_use]
-    #[track_caller]
-    pub fn is_buffer(&self) -> bool {
-        self.borrow().as_buffer().is_some()
-    }
-
     /// Converts an object to a primitive.
     ///
     /// Diverges from the spec to prevent a stack overflow when the object is recursive.
@@ -535,6 +545,30 @@ Cannot both specify accessors and a value or writable attribute",
         }
         None
     }
+
+    /// Casts to a `BufferObject` if the object is an `ArrayBuffer` or a `SharedArrayBuffer`.
+    #[inline]
+    pub(crate) fn into_buffer_object(self) -> Result<BufferObject, JsObject> {
+        let obj = self.borrow();
+
+        if obj.is::<ArrayBuffer>() {
+            drop(obj);
+            // SAFETY: We have verified that the inner data of `self` is of type `ArrayBuffer`.
+            return Ok(BufferObject::Buffer(unsafe {
+                self.downcast_unchecked::<ArrayBuffer>()
+            }));
+        }
+        if obj.is::<SharedArrayBuffer>() {
+            drop(obj);
+            // SAFETY: We have verified that the inner data of `self` is of type `SharedArrayBuffer`.
+            return Ok(BufferObject::SharedBuffer(unsafe {
+                self.downcast_unchecked::<SharedArrayBuffer>()
+            }));
+        }
+        drop(obj);
+
+        Err(self)
+    }
 }
 
 impl<T: NativeObject + ?Sized> JsObject<T> {

core/engine/src/object/mod.rs

@@ -10,7 +10,6 @@ use thin_vec::ThinVec;
 use self::{internal_methods::ORDINARY_INTERNAL_METHODS, shape::Shape};
 use crate::{
     builtins::{
-        array_buffer::{ArrayBuffer, BufferRef, BufferRefMut, SharedArrayBuffer},
         function::{
             arguments::{MappedArguments, UnmappedArguments},
             ConstructorKind,
@@ -352,33 +351,6 @@ impl Object<dyn NativeObject> {
         self.data.downcast_mut::<T>()
     }
 
-    /// Gets the buffer data if the object is an `ArrayBuffer` or a `SharedArrayBuffer`.
-    #[inline]
-    #[must_use]
-    pub(crate) fn as_buffer(&self) -> Option<BufferRef<'_>> {
-        if let Some(buffer) = self.downcast_ref::<ArrayBuffer>() {
-            return Some(BufferRef::Buffer(buffer));
-        }
-        self.downcast_ref::<SharedArrayBuffer>()
-            .map(BufferRef::SharedBuffer)
-    }
-
-    /// Gets the mutable buffer data if the object is an `ArrayBuffer` or a `SharedArrayBuffer`.
-    #[inline]
-    pub(crate) fn as_buffer_mut(&mut self) -> Option<BufferRefMut<'_>> {
-        // Workaround for Problem case 3 of the current borrow checker.
-        // https://rust-lang.github.io/rfcs/2094-nll.html#problem-case-3-conditional-control-flow-across-functions
-        if self.is::<ArrayBuffer>() {
-            match self.downcast_mut::<ArrayBuffer>() {
-                Some(buffer) => return Some(BufferRefMut::Buffer(buffer)),
-                None => unreachable!(),
-            }
-        }
-
-        self.downcast_mut::<SharedArrayBuffer>()
-            .map(BufferRefMut::SharedBuffer)
-    }
-
     /// Checks if this object is an `Arguments` object.
     pub(crate) fn is_arguments(&self) -> bool {
         self.is::<UnmappedArguments>() || self.is::<MappedArguments>()