LibJS: Implement the ArrayBuffer.prototype.detached getter

Userland/Libraries/LibJS/Runtime/ArrayBufferPrototype.cpp

@@ -26,6 +26,7 @@ ThrowCompletionOr<void> ArrayBufferPrototype::initialize(Realm& realm)
     u8 attr = Attribute::Writable | Attribute::Configurable;
     define_native_function(realm, vm.names.slice, slice, 2, attr);
     define_native_accessor(realm, vm.names.byteLength, byte_length_getter, {}, Attribute::Configurable);
+    define_native_accessor(realm, vm.names.detached, detached_getter, {}, Attribute::Configurable);
 
     // 25.1.5.4 ArrayBuffer.prototype [ @@toStringTag ], https://tc39.es/ecma262/#sec-arraybuffer.prototype-@@tostringtag
     define_direct_property(vm.well_known_symbol_to_string_tag(), PrimitiveString::create(vm, vm.names.ArrayBuffer.as_string()), Attribute::Configurable);
@@ -148,4 +149,18 @@ JS_DEFINE_NATIVE_FUNCTION(ArrayBufferPrototype::byte_length_getter)
     return Value(length);
 }
 
+// 25.1.5.4 get ArrayBuffer.prototype.detached, https://tc39.es/proposal-arraybuffer-transfer/#sec-get-arraybuffer.prototype.detached
+JS_DEFINE_NATIVE_FUNCTION(ArrayBufferPrototype::detached_getter)
+{
+    // 1. Let O be the this value.
+    // 2. Perform ? RequireInternalSlot(O, [[ArrayBufferData]]).
+    auto array_buffer_object = TRY(typed_this_value(vm));
+
+    // 3. If IsSharedArrayBuffer(O) is true, throw a TypeError exception.
+    // FIXME: Check for shared buffer
+
+    // 4. Return IsDetachedBuffer(O).
+    return Value(array_buffer_object->is_detached());
+}
+
 }

Userland/Libraries/LibJS/Runtime/ArrayBufferPrototype.h

@@ -23,6 +23,7 @@ private:
 
     JS_DECLARE_NATIVE_FUNCTION(slice);
     JS_DECLARE_NATIVE_FUNCTION(byte_length_getter);
+    JS_DECLARE_NATIVE_FUNCTION(detached_getter);
 };
 
 }

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -150,6 +150,7 @@ namespace JS {
     P(deleteProperty)                        \
     P(deref)                                 \
     P(description)                           \
+    P(detached)                              \
     P(difference)                            \
     P(dir)                                   \
     P(direction)                             \