refactor: migrate require_internal_slot! from downcast_ref to downcast

Switch the require_internal_slot! macro to use JsObject::downcast instead
of downcast_ref, returning JsObject<T> (owned handle) rather than Ref<T>.
This prevents GcRefCell borrow panics by ensuring borrows are only held
for the duration of specific read/write operations.

Updated all call sites across 20 built-in modules to use
.borrow().data() / .borrow_mut().data_mut() for inner field access:
- Date (renamed macro binding to date_obj in setters to avoid shadowing)
- Temporal (Duration, Instant, PlainDate, PlainDateTime, PlainTime,
  PlainMonthDay, PlainYearMonth, ZonedDateTime)
- ArrayBuffer, SharedArrayBuffer, DataView, TypedArray
- WeakRef, WeakMap, WeakSet
- Intl (Collator, Segmenter, Segments)

Author: Nakshatra480

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

@@ -496,12 +496,12 @@ impl ArrayBuffer {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
         // 3. If IsSharedArrayBuffer(O) is true, throw a TypeError exception.
-        require_internal_slot!(buf = this, Self, "ArrayBuffer");
+        let buf = require_internal_slot!(this, Self, "ArrayBuffer");
 
         // 4. If IsDetachedBuffer(O) is true, return +0𝔽.
         // 5. Let length be O.[[ArrayBufferByteLength]].
         // 6. Return 𝔽(length).
-        Ok(buf.len().into())
+        Ok(buf.borrow().data().len().into())
     }
 
     /// [`get ArrayBuffer.prototype.maxByteLength`][spec].
@@ -515,10 +515,12 @@ impl ArrayBuffer {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
         // 3. If IsSharedArrayBuffer(O) is true, throw a TypeError exception.
-        require_internal_slot!(buf = this, Self, "ArrayBuffer");
+        let buf = require_internal_slot!(this, Self, "ArrayBuffer");
 
         // 4. If IsDetachedBuffer(O) is true, return +0𝔽.
-        let Some(data) = buf.bytes() else {
+        let buf_data = buf.borrow();
+        let buf_data = buf_data.data();
+        let Some(data) = buf_data.bytes() else {
             return Ok(JsValue::from(0));
         };
 
@@ -527,7 +529,7 @@ impl ArrayBuffer {
         // 6. Else,
         //     a. Let length be O.[[ArrayBufferMaxByteLength]].
         // 7. Return 𝔽(length).
-        Ok(buf.max_byte_len.unwrap_or(data.len() as u64).into())
+        Ok(buf_data.max_byte_len.unwrap_or(data.len() as u64).into())
     }
 
     /// [`get ArrayBuffer.prototype.resizable`][spec].
@@ -541,10 +543,10 @@ impl ArrayBuffer {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
         // 3. If IsSharedArrayBuffer(O) is true, throw a TypeError exception.
-        require_internal_slot!(buf = this, Self, "ArrayBuffer");
+        let buf = require_internal_slot!(this, Self, "ArrayBuffer");
 
         // 4. If IsFixedLengthArrayBuffer(O) is false, return true; otherwise return false.
-        Ok(JsValue::from(!buf.is_fixed_len()))
+        Ok(JsValue::from(!buf.borrow().data().is_fixed_len()))
     }
 
     /// [`get ArrayBuffer.prototype.detached`][spec].
@@ -559,10 +561,10 @@ impl ArrayBuffer {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
         // 3. If IsSharedArrayBuffer(O) is true, throw a TypeError exception.
-        require_internal_slot!(buf = this, Self, "ArrayBuffer");
+        let buf = require_internal_slot!(this, Self, "ArrayBuffer");
 
         // 4. Return IsDetachedBuffer(O).
-        Ok(buf.is_detached().into())
+        Ok(buf.borrow().data().is_detached().into())
     }
 
     /// [`ArrayBuffer.prototype.resize ( newLength )`][spec].

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

@@ -225,10 +225,10 @@ impl SharedArrayBuffer {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
         // 3. If IsSharedArrayBuffer(O) is true, throw a TypeError exception.
-        require_internal_slot!(buf = this, Self, "SharedArrayBuffer");
+        let buf = require_internal_slot!(this, Self, "SharedArrayBuffer");
 
         // 4. Let length be ArrayBufferByteLength(O, seq-cst).
-        let len = buf.bytes(Ordering::SeqCst).len() as u64;
+        let len = buf.borrow().data().bytes(Ordering::SeqCst).len() as u64;
 
         // 5. Return 𝔽(length).
         Ok(len.into())
@@ -245,10 +245,10 @@ impl SharedArrayBuffer {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
         // 3. If IsSharedArrayBuffer(O) is false, throw a TypeError exception.
-        require_internal_slot!(buf = this, Self, "SharedArrayBuffer");
+        let buf = require_internal_slot!(this, Self, "SharedArrayBuffer");
 
         // 4. If IsFixedLengthArrayBuffer(O) is false, return true; otherwise return false.
-        Ok(JsValue::from(!buf.is_fixed_len()))
+        Ok(JsValue::from(!buf.borrow().data().is_fixed_len()))
     }
 
     /// [`get SharedArrayBuffer.prototype.maxByteLength`][spec].
@@ -262,14 +262,14 @@ impl SharedArrayBuffer {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
         // 3. If IsSharedArrayBuffer(O) is false, throw a TypeError exception.
-        require_internal_slot!(buf = this, Self, "SharedArrayBuffer");
+        let buf = require_internal_slot!(this, Self, "SharedArrayBuffer");
 
         // 4. If IsFixedLengthArrayBuffer(O) is true, then
         //     a. Let length be O.[[ArrayBufferByteLength]].
         // 5. Else,
         //     a. Let length be O.[[ArrayBufferMaxByteLength]].
         // 6. Return 𝔽(length).
-        Ok(buf.data.buffer.len().into())
+        Ok(buf.borrow().data().data.buffer.len().into())
     }
 
     /// [`SharedArrayBuffer.prototype.grow ( newLength )`][spec].

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

@@ -331,10 +331,11 @@ impl DataView {
     ) -> JsResult<JsValue> {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[DataView]]).
-        require_internal_slot!(view = this, Self, "DataView");
+        let view = require_internal_slot!(this, Self, "DataView");
         // 3. Assert: O has a [[ViewedArrayBuffer]] internal slot.
         // 4. Let buffer be O.[[ViewedArrayBuffer]].
-        let buffer = view.viewed_array_buffer.clone();
+        let view_data = view.borrow();
+        let buffer = view_data.data().viewed_array_buffer.clone();
         // 5. Return buffer.
         Ok(buffer.into())
     }
@@ -357,22 +358,24 @@ impl DataView {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[DataView]]).
         // 3. Assert: O has a [[ViewedArrayBuffer]] internal slot.
-        require_internal_slot!(view = this, Self, "DataView");
+        let view = require_internal_slot!(this, Self, "DataView");
 
         // 4. Let viewRecord be MakeDataViewWithBufferWitnessRecord(O, seq-cst).
         // 5. If IsViewOutOfBounds(viewRecord) is true, throw a TypeError exception.
-        let buffer = view.viewed_array_buffer.as_buffer();
+        let view_data = view.borrow();
+        let buffer = view_data.data().viewed_array_buffer.as_buffer();
         let Some(slice) = buffer
             .bytes(Ordering::SeqCst)
-            .filter(|s| !view.is_out_of_bounds(s.len()))
+            .filter(|s| !view.borrow().data().is_out_of_bounds(s.len()))
         else {
             return Err(JsNativeError::typ()
                 .with_message("view out of bounds for its inner buffer")
                 .into());
         };
 
         // 6. Let size be GetViewByteLength(viewRecord).
-        let size = view.byte_length(slice.len());
+        let view_data = view.borrow();
+        let size = view_data.data().byte_length(slice.len());
 
         // 7. Return 𝔽(size).
         Ok(size.into())
@@ -396,15 +399,16 @@ impl DataView {
     ) -> JsResult<JsValue> {
         // 1. Let O be the this value.
         // 2. Perform ? RequireInternalSlot(O, [[DataView]]).
-        require_internal_slot!(view = this, Self, "DataView");
+        let view = require_internal_slot!(this, Self, "DataView");
 
         // 3. Assert: O has a [[ViewedArrayBuffer]] internal slot.
-        let buffer = view.viewed_array_buffer.as_buffer();
+        let view_data = view.borrow();
+        let buffer = view_data.data().viewed_array_buffer.as_buffer();
         // 4. Let viewRecord be MakeDataViewWithBufferWitnessRecord(O, seq-cst).
         // 5. If IsViewOutOfBounds(viewRecord) is true, throw a TypeError exception.
         if buffer
             .bytes(Ordering::SeqCst)
-            .filter(|b| !view.is_out_of_bounds(b.len()))
+            .filter(|b| !view.borrow().data().is_out_of_bounds(b.len()))
             .is_none()
         {
             return Err(JsNativeError::typ()
@@ -413,7 +417,8 @@ impl DataView {
         }
 
         // 6. Let offset be O.[[ByteOffset]].
-        let offset = view.byte_offset;
+        let view_data = view.borrow();
+        let offset = view_data.data().byte_offset;
         // 7. Return 𝔽(offset).
         Ok(offset.into())
     }
@@ -436,7 +441,7 @@ impl DataView {
     ) -> JsResult<JsValue> {
         // 1. Perform ? RequireInternalSlot(view, [[DataView]]).
         // 2. Assert: view has a [[ViewedArrayBuffer]] internal slot.
-        require_internal_slot!(view = view, Self, "DataView");
+        let view = require_internal_slot!(view, Self, "DataView");
 
         // 3. Let getIndex be ? ToIndex(requestIndex).
         let get_index = request_index.to_index(context)?;
@@ -447,21 +452,24 @@ impl DataView {
         // 6. Let viewRecord be MakeDataViewWithBufferWitnessRecord(view, unordered).
         // 7. NOTE: Bounds checking is not a synchronizing operation when view's backing buffer is a growable SharedArrayBuffer.
         // 8. If IsViewOutOfBounds(viewRecord) is true, throw a TypeError exception.
-        let buffer = view.viewed_array_buffer.as_buffer();
+        let view_data = view.borrow();
+        let buffer = view_data.data().viewed_array_buffer.as_buffer();
         let Some(data) = buffer
             .bytes(Ordering::Relaxed)
-            .filter(|buf| !view.is_out_of_bounds(buf.len()))
+            .filter(|buf| !view.borrow().data().is_out_of_bounds(buf.len()))
         else {
             return Err(JsNativeError::typ()
                 .with_message("view out of bounds for its inner buffer")
                 .into());
         };
 
         // 5. Let viewOffset be view.[[ByteOffset]].
-        let view_offset = view.byte_offset;
+        let view_data = view.borrow();
+        let view_offset = view_data.data().byte_offset;
 
         // 9. Let viewSize be GetViewByteLength(viewRecord).
-        let view_size = view.byte_length(data.len());
+        let view_data = view.borrow();
+        let view_size = view_data.data().byte_length(data.len());
 
         // 10. Let elementSize be the Element Size value specified in Table 71 for Element Type type.
         let element_size = size_of::<T>() as u64;
@@ -774,7 +782,7 @@ impl DataView {
     ) -> JsResult<JsValue> {
         // 1. Perform ? RequireInternalSlot(view, [[DataView]]).
         // 2. Assert: view has a [[ViewedArrayBuffer]] internal slot.
-        require_internal_slot!(view = view, Self, "DataView");
+        let view = require_internal_slot!(view, Self, "DataView");
 
         // 3. Let getIndex be ? ToIndex(requestIndex).
         let get_index = request_index.to_index(context)?;
@@ -789,22 +797,28 @@ impl DataView {
         // 8. Let viewRecord be MakeDataViewWithBufferWitnessRecord(view, unordered).
         // 9. NOTE: Bounds checking is not a synchronizing operation when view's backing buffer is a growable SharedArrayBuffer.
         // 10. If IsViewOutOfBounds(viewRecord) is true, throw a TypeError exception.
-        let mut buffer = view.viewed_array_buffer.as_buffer_mut();
+        let viewed_buffer = {
+            let view_data = view.borrow();
+            view_data.data().viewed_array_buffer.clone()
+        };
+        let mut buffer = viewed_buffer.as_buffer_mut();
 
         let Some(mut data) = buffer
             .bytes(Ordering::Relaxed)
-            .filter(|buf| !view.is_out_of_bounds(buf.len()))
+            .filter(|buf| !view.borrow().data().is_out_of_bounds(buf.len()))
         else {
             return Err(JsNativeError::typ()
                 .with_message("view out of bounds for its inner buffer")
                 .into());
         };
 
         // 11. Let viewSize be GetViewByteLength(viewRecord).
-        let view_size = view.byte_length(data.len());
+        let view_data = view.borrow();
+        let view_size = view_data.data().byte_length(data.len());
 
         // 7. Let viewOffset be view.[[ByteOffset]].
-        let view_offset = view.byte_offset;
+        let view_data = view.borrow();
+        let view_offset = view_data.data().byte_offset;
 
         // 12. Let elementSize be the Element Size value specified in Table 71 for Element Type type.
         let elem_size = size_of::<T>();