parsing - Unindented code breaks my grammar -

i have .g4 grammar vba/vb6 lexer/parser, lexer skipping line continuation tokens - not skipping them breaks parser , isn't option. here's lexer rule in question:

line_continuation : ' ' '_' '\r'? '\n' -> skip; 

the problem causing, whenever continued line starts @ column 1, parser blows up:

sub test() debug.print "some text " & _ vbnewline & "some more text"     end sub 

i thought "hey know! i'll pre-process string i'm feeding antlr insert whitespace before underscore, , change grammar accept it!"

so changed rule this:

line_continuation : ws? ws '_' newline -> skip; newline : ws? ('\r'? '\n') ws?;  ws : [ \t]+; 

...and test vba code above gave me parser error:

extraneous input 'vbnewline' expecting ws

for solution tell users indent code. there way can fix grammar rule?

_{(full vba.g4 grammar file on github)}

you want line continuation treated whitespace.

ok, add lexical definition of line continuation ws token. ws pick line continuation, , don't need linecontinuation anywhere.

//line_continuation : ' ' '_' '\r'? '\n' -> skip; newline : ws? ('\r'? '\n') ws?;  ws : ([ \t]+)|(' ' '_' '\r'? '\n');