make suggested changes

boa/src/builtins/array/mod.rs

@@ -281,22 +281,21 @@ impl Array {
     /// Returns a Boolean valued property that if `true` indicates that
     /// an object should be flattened to its array elements
     /// by `Array.prototype.concat`.
-
-    pub(crate) fn is_concat_spreadable(this: &Value, context: &mut Context) -> bool {
+    pub(crate) fn is_concat_spreadable(this: &Value, context: &mut Context) -> Result<bool> {
         if !this.is_object() {
-            return false;
+            return Ok(false);
         }
         let spreadable = this
             .get_field(WellKnownSymbols::is_concat_spreadable(), context)
             .unwrap_or(Value::undefined());
 
         if !spreadable.is_undefined() {
-            return spreadable.to_boolean();
+            return Ok(spreadable.to_boolean());
         }
 
         match this.as_object() {
-            Some(obj) => obj.is_array(),
-            _ => false,
+            Some(obj) => Ok(obj.is_array()),
+            _ => Ok(false),
         }
     }