anchor.diff:   | attributes? declaration_modifiers? 'init' '!'
    ;
   
  -initializer_body : code_block  ;
  +initializer_body : code_block ;
   
   // GRAMMAR OF A DEINITIALIZER DECLARATION
   
  
positive.code: 
  top_level : statement* EOF ;
  
  // Statements
  
  // GRAMMAR OF A STATEMENT
  
  statement
  
negative.code: 
  statements : statement+ ;
  
  // GRAMMAR OF A LOOP STATEMENT
  
  loop_statement
   : for_in_statement
   | while_statement
   | repeat_while_statement
   ;
  
  // GRAMMAR OF A FOR_IN STATEMENT
  
  for_in_statement : 'for' 'case'? pattern 'in' expression where_clause? code_block  ;
  
  // GRAMMAR OF A WHILE STATEMENT
  
  while_statement : 'while' condition_list code_block  ;
  
  condition_list : condition (',' condition)* ;
  condition
  