Specifies the sources of precompiled assemblies referenced during compilation.
This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.
| UserAssembly | Matches precompiled assemblies present in the project and packages. | 
| UnityEngine | Matches UnityEngine and runtime module assemblies. | 
| UnityEditor | Matches UnityEditor and editor module assemblies. | 
| SystemAssembly | Matches assemblies supplied by the target framework. | 
| All | Matches all assembly sources. |