grammar Example;

options {
	k=1;
	output=AST;
	}

entry
    :
      (my_rule)+
    ;

my_rule
	:
	  tf_port_item SEMI
	;

tf_port_item
   : 
     data_type ID variable_dimension
   ;

    
data_type
    :
      'bit'
    | 'byte'
    | 'real' // Comment this to suppress NoViableAlt
    | 'struct' 
    | 'union' ( 'tagged' )? 
    | 'enum' 
    | 'virtual'
    | ps_identifier 
    ;

ps_identifier
   :
     ( ID COLON_COLON ) => ID COLON_COLON ID 
   | ID
   ;
	
variable_dimension
    :
        ( associative_dimension_1 ) => associative_dimension_1 variable_dimension    // comment this line
//        ( associative_dimension_2 ) => associative_dimension_2 variable_dimension  // and uncomment this one to suppress NoViableAlt ( with 'real' alt in data_type)
    | ( sized_or_unsized_dimension )*
    ;

associative_dimension_1
    :
      LBRACK ( STAR | data_type ) RBRACK
    ;      

associative_dimension_2
	    :
        ( LBRACK STAR ) => LBRACK STAR RBRACK
      | LBRACK data_type RBRACK
	    ;

      
sized_or_unsized_dimension 
    :
      LBRACK ( NUMBER )? RBRACK 
    ;
     
/********** Lexer *************/

SEMI: ';';
STAR: '*';
LBRACK: '[';
RBRACK: ']';
COLON_COLON: '::';
     
WS
    :
      (' '|'\r'|'\t'|'\u000C'|'\n') {$channel=HIDDEN;}
    ;

ID
    :
      ('a'..'z'|'A'..'Z'|'_') ('0'..'9'|'a'..'z'|'A'..'Z'|'_')*
    ;

NUMBER
    :
      ('0'..'9')+
    ;