csharplang/proposals/GlobalUsingDirective.md

Global Using Directive

Syntax for a using directive is extended with an optional global keyword that can precede the using keyword:

using_directive
  : 'global'? 'using' ('static' | name_equals)? name ';'
  ;

• Global Using Directives are allowed only on the Compilation Unit level (cannot be used inside a namespace declaration).
• Global Using directives, if any, must precede any non-global using directives.
• The scope of a Global Using Directive extends over the namespace member declarations and non-global using directives of all compilation units within the program. The scope of a Global Using Directive specifically does not include other Global Using Directives. Thus, peer Global Using Directives or those from a different compilation unit do not affect each other, and the order in which they are written is insignificant.