anchor.diff:  
   // GRAMMAR OF A GENERIC PARAMETER CLAUSE
   
  -generic_parameter_clause : '<' generic_parameter_list requirement_clause?'>'  ;
  +generic_parameter_clause : '<' generic_parameter_list requirement_clause? '>'  ;
   generic_parameter_list : generic_parameter | generic_parameter ',' generic_parameter_list  ;
   generic_parameter : type_name | type_name ':' type_identifier | type_name ':' protocol_composition_type  ;
   requirement_clause : 'where' requirement_list  ;
  
positive.code:  */
  grammar Swift;
  
  // "The top-level code in a Swift source file consists of zero or more statements, declarations, and expressions."
  top_level : (statement | declaration | expression)* EOF ;
  
  // Statements
  
  // GRAMMAR OF A STATEMENT
  
  statement : expression ';'?
   | declaration ';'?
   | loop_statement ';'?
   | branch_statement ';'?
  
negative.code: // GRAMMAR OF A CLASS DECLARATION
  
  class_declaration : attributes? 'class' class_name generic_parameter_clause? type_inheritance_clause? class_body  ;
  class_name : identifier ;
  class_body : '{' declarations? '}'  ;
  
  // GRAMMAR OF A PROTOCOL DECLARATION
  
  