Using for with global binding.

docs/contracts/using-for.rst

@@ -42,6 +42,13 @@ scope (either the contract or the current module/source unit),
 including within all of its functions, and has no effect
 outside of the contract or module in which it is used.
 
+When the directive is used at file level and applied to a
+user-defined type which was defined at file level in the same file,
+the word ``global`` can be added at the end. This will have the
+effect that the functions are attached to the type everywhere
+the type is available (including other files), not only in the
+scope of the using statement.
+
 Let us rewrite the set example from the
 :ref:`libraries` section in this way, using file-level functions
 instead of library functions.

docs/grammar/SolidityLexer.g4

@@ -47,6 +47,7 @@ FixedBytes:
 	'bytes25' | 'bytes26' | 'bytes27' | 'bytes28' | 'bytes29' | 'bytes30' | 'bytes31' | 'bytes32';
 For: 'for';
 Function: 'function';
+Global: 'global'; // not a real keyword
 Hex: 'hex';
 If: 'if';
 Immutable: 'immutable';

docs/grammar/SolidityParser.g4

@@ -315,7 +315,7 @@ errorDefinition:
  * Using directive to bind library functions and free functions to types.
  * Can occur within contracts and libraries and at the file level.
  */
-usingDirective: Using (identifierPath | (LBrace identifierPath (Comma identifierPath)* RBrace)) For (Mul | typeName) Semicolon;
+usingDirective: Using (identifierPath | (LBrace identifierPath (Comma identifierPath)* RBrace)) For (Mul | typeName) Global? Semicolon;
 /**
  * A type name can be an elementary type, a function type, a mapping type, a user-defined type
  * (e.g. a contract or struct) or an array type.
@@ -389,7 +389,7 @@ inlineArrayExpression: LBrack (expression ( Comma expression)* ) RBrack;
 /**
  * Besides regular non-keyword Identifiers, some keywords like 'from' and 'error' can also be used as identifiers.
  */
-identifier: Identifier | From | Error | Revert;
+identifier: Identifier | From | Error | Revert | Global;
 
 literal: stringLiteral | numberLiteral | booleanLiteral | hexStringLiteral | unicodeStringLiteral;
 booleanLiteral: True | False;