small fixes

Author: LFDanLu

packages/react-aria-components/src/Separator.tsx

@@ -29,7 +29,8 @@ export class SeparatorNode extends CollectionNode<any> {
   }
 
   filter(collection: BaseCollection<any>, newCollection: BaseCollection<any>): CollectionNode<any> | null {
-    if (newCollection.getItem(this.prevKey!)) {
+    let prevItem = newCollection.getItem(this.prevKey!);
+    if (prevItem && prevItem.type !== 'separator') {
       return this.clone();
     }
 

packages/react-aria-components/src/Table.tsx

@@ -18,10 +18,6 @@ import React, {createContext, ForwardedRef, forwardRef, JSX, ReactElement, React
 import ReactDOM from 'react-dom';
 import {UNSTABLE_InternalAutocompleteContext} from './Autocomplete';
 
-export type Mutable<T> = {
-  -readonly[P in keyof T]: T[P]
-}
-
 class TableCollection<T> extends BaseCollection<T> implements ITableCollection<T> {
   headerRows: GridNode<T>[] = [];
   columns: GridNode<T>[] = [];