Editor/Assembly.cs

Assembly-level global using directives for the Editor assembly. Declares common namespaces (System, collections, IO, LINQ, Sandbox, Editor) as global so they are available across the assembly.

File Access
// What the game's editor assembly used to supply from elsewhere. System and System.IO arrived here by accident -
// Editor/Retargeting declared them global, and a global using is assembly-wide - so the tool was written against
// them without ever importing them. They are stated here rather than added to 22 files.
global using System;
global using System.Collections.Generic;
global using System.IO;
global using System.Linq;
global using Sandbox;
global using Editor;