Require newline or EOF after statement match

Question

Just looking for a simple way of getting ANTLR4 to generate a parser that will do the following (ignore anything after the ;):

int #i ;    defines an int
int #j ;    see how I have to go to another line for another statement?

My parser is as the following:

compilationUnit:
    (statement END?)*
    statement END?
    EOF
;

statement:
    intdef |
    WS
;

// 10 - 1F block.

intdef:
    'intdef' Identifier
;

// Lexer.

Identifier: '#' Letter LetterOrDigit*;
fragment Letter: [a-zA-Z_];
fragment LetterOrDigit: [a-zA-Z0-9$_];

// Whitespace, fragments and terminals.

WS: [ \t\r\n\u000C]+ -> skip;
//COMMENT: '/*' .*? '*/' -> channel(HIDDEN);
END: (';' ~[\r\n]*) | '\n';

In essence, any time I have a statement, I need it to REQUIRE a newline before another is entered. I don't care if there's 3 new lines and then on the second one a bunch of tabs persist, as long as there's a new line.

The issue is, the ANTLR4 Parse Tree seems to be giving me errors for inputs such as:

.

(Pretend the dot isnt there, its literally no input)

int #i int #j

Woops, we got two on the same line!

Any ideas on how I can achieve this? I appreciate the help.

Answer 1

I've simplified your grammar a bit but made it require an end-of-line sequence after each statement to parse correctly.

grammar Testnl;

program: (statement )* EOF ;

statement: 'int' Identifier EOL;

Identifier: '#' Letter LetterOrDigit*;
fragment Letter: [a-zA-Z_];
fragment LetterOrDigit: [a-zA-Z0-9$_];

EOL: ';' .*? '\r\n'
| ';' .*? '\n'
;

WS: [ \t\r\n\u000C]+ -> skip;

It parses

int #i ;
int #j;


[@0,0:2='int',<'int'>,1:0]
[@1,4:5='#i',<Identifier>,1:4]
[@2,7:9=';\r\n',<EOL>,1:7]
[@3,10:12='int',<'int'>,2:0]
[@4,14:15='#j',<Identifier>,2:4]
[@5,16:18=';\r\n',<EOL>,2:6]
[@6,19:18='<EOF>',<EOF>,3:0]

It also ignore stuff after the semicolon as just part of the EOL token:

[@0,0:2='int',<'int'>,1:0]
[@1,4:5='#i',<Identifier>,1:4]
[@2,7:20='; ignore this\n',<EOL>,1:7]
[@3,21:23='int',<'int'>,2:0]
[@4,25:26='#j',<Identifier>,2:4]
[@5,27:28=';\n',<EOL>,2:6]
[@6,29:28='<EOF>',<EOF>,3:0]

using either linefeed or carriagereturn-linefeed just fine. Is that what you're looking for?

EDIT

Per OP comment, made a small change to allow consecutive EOL tokens, and also move EOL token to statement to reduce repetition:

grammar Testnl;

program: ( statement EOL )* EOF ;

statement: 'int' Identifier;

Identifier: '#' Letter LetterOrDigit*;
fragment Letter: [a-zA-Z_];
fragment LetterOrDigit: [a-zA-Z0-9$_];

EOL: ';' .*? ('\r\n')+
| ';' .*? ('\n')+
;

WS: [ \t\r\n\u000C]+ -> skip;