Hello people,
I know there are newbies (like me) asking all the time why a grammar fails, or how to disambiguate, etc., and that must be utterly boring/irritating.

But I really can't figure out why it does that.

My complete grammar is actually much more complex, but I've stripped it down to the simplest version (one single rule) to find the cause of the issue, and still can't find it.


======== on to the issue ==========

Below you'll find a simple grammar.

Yet, when I feed it with this (a text file containing nothing else), it fails to recognize it :
/** @pluginName:   agsMyPlugin2 **/

The error message is :
line 1:0 no viable alternative at input '/** @pluginName:   agsMyPlugin2 **/ '

The grammar is below.



========== actual grammar =============

grammar EasyPluginGrammar;


options {
  language = Java;

  output = AST; //we tell ANTLR that we want to produce a crawlable tree
  ASTLabelType = CommonTree; // each node of the tree will be of type "CommonTree"
}

tokens { 
  SPECIALCOMMENTTAG;
  RAWSPECIALCOMMENT;
  NOSPECIALCOMMENT;
 }

 

plugin
      : specialComment EOF!
      ;



specialComment
        : '/**' '@' scTag ':' scValue '**/' -> SPECIALCOMMENTTAG scTag scValue
        | -> NOSPECIALCOMMENT
        ;
       
scTag : IDENT ;

scValue : RSC_TEXT //I also tried with "IDENT" instead of "RSC_TEXT"
        ;
 

fragment LETTER : 'a'..'z'|'A'..'Z' ;
fragment DIGIT : '0'..'9' ;
     
IDENT  : ( LETTER ) ( LETTER | DIGIT )* ;
 
INTEGER : DIGIT + ;


RSC_TEXT : ( ASCII_EXCEPT_BACKSLASH )+ ;

fragment ASCII_EXCEPT_BACKSLASH : ' '..'[' | ']'..'~' ;


WS   :   ( ' ' | '\t' | '\r' | '\n' ) {$channel=HIDDEN;};


fragment
EXPONENT : ('e'|'E') ('+'|'-')? ('0'..'9')+ ;

fragment
HEX_DIGIT : (DIGIT|'a'..'f'|'A'..'F') ;

fragment
ESC_SEQ
    :   '\\' ('b'|'t'|'n'|'f'|'r'|'\"'|'\''|'\\')
    |   UNICODE_ESC
    |   OCTAL_ESC
    ;

fragment
OCTAL_ESC
    :   '\\' ('0'..'3') ('0'..'7') ('0'..'7')
    |   '\\' ('0'..'7') ('0'..'7')
    |   '\\' ('0'..'7')
    ;

fragment
UNICODE_ESC
    :   '\\' 'u' HEX_DIGIT HEX_DIGIT HEX_DIGIT HEX_DIGIT
    ;