anchor.diff:                  TOKENDMODULE [ COLON  VAR ]
               )
   
  -    rule func_or_module_declaration:
  -          function_declaration
  -        | TOKMODULE [ LBRACKET assign_rvalue RBRACKET ] typevar_item_or_var
  -            [ typevar_param_list ]
  -            [ provisos_clause ] SEMICOLON
  -            [
  -                (   TOKENDMODULE [ COLON VAR]
  -                |   ( module_contents_declaration | single_statement)+
  -                    TOKENDMODULE [ COLON VAR]
  -                )
  -            ]
  -
       rule dep_item:
           VAR TOKDETERMINES VAR
   
  
positive.code: 
      rule module_contents_declaration:
            interface_declaration [SEMICOLON]
          | func_or_module_declaration
          | method_declaration
          | TOKTYPEDEF ( single_type_definition | NUM VAR SEMICOLON )
          | TOKIMPORT
              ( CLASSVAR STAR SEMICOLON
  
negative.code:         | TOKEXPORT VAR [ LPAREN DOT DOT RPAREN ] SEMICOLON
          | TOKINSTANCE typevar_item
              [ provisos_clause ] SEMICOLON
              ( module_contents_declaration )*
              TOKENDINSTANCE [ COLON VAR ]
          | let_statement
          | rule_statement
          | TOKTYPECLASS typevar_item
              [ TOKDEPENDENCIES LPAREN dep_item (COMMA dep_item)* RPAREN ]
              SEMICOLON
              ( module_contents_declaration )*
              TOKENDTYPECLASS [ COLON VAR ]
  
      rule goal:
  