[antlr-interest] Syntax for token accumulation

[Gavin Lambert]

At 13:55 21/03/2008, Olivier Lefevre wrote:
 >Assume ID is a valid lexer token. (list+=ID)* works as you'd 
expect
 >but (list+=(tok=ID))* does not, although it compiles: when the 
rule
 >exits the list in question is null. I had a look at the Java 
code
 >and the list is indeed not even initialized. Even merely
 >parenthesizing ID as in: ((list+=(ID))* gives the same null 
result.
 >It would be useful for this syntax to be supported, though. Is 
it
 >indeed an ANTLR limitation?

Yes (for the moment anyway).

But you can extract it to a subrule and then it will work:

a : (list+=b)* { ... };
b : tok=ID { ... };