I'm trying to create a Beginning-Of-Line token:
lexer grammar ScriptLexer;
BOL : {getCharPositionInLine() == 0;}; // Beginning Of Line token
But the above emits the error
The name 'getCharPositionInLine' does not exist in the current context
As it creates this code:
private void BOL_action(RuleContext _localctx, int actionIndex) {
switch (actionIndex) {
case 0: getCharPositionInLine() == 0; break;
}
}
Where the getCharPositionInLine() method doesn't exist...
Simplest approach is to just recognize an EOL as the corresponding BOL token.
BC : '/*' .*? '*/' -> channel(HIDDEN) ;
LC : '//' ~[\r\n]* -> channel(HIDDEN) ;
HWS : [ \t]* -> channel(HIDDEN) ;
BOL : [\r\n\f]+ ;
Rules like a block comment rule will consume the EOLs internally, so no problem there. Rules like a line comment will not consume the EOL, so a proper BOL will be emitted for the line immediately following.
A potential problem is that no BOL will be emitted for the beginning of input. Simplest way to handle this is to force prefix the input text with a line terminal before feeding it to the lexer.
来源：https://stackoverflow.com/questions/31903723/how-to-detect-beginning-of-line-or-the-name-getcharpositioninline-does-not