[antlr-interest] BUG?: Difference between AntlrWorks and antlr grammars? - Was "how to emit separate ASTs for 'int a,b; '"

[Austin Hastings]

I believe this is down to the differences between superclassing with 
Debug and using the debugger adaptors, but I'm far from an expert.
 
I feed the following line into my grammar:

    int a,b;

When I run the antlrworks debugger, and fast-forward to the end, I can 
view the AST and see a tree that (graphically) looks like:

^(nil
    ^(DECL int a)
    ^(DECL b)
)

More graphically:

       nil
     /    \
  DECL   DECL
 /   \     |
int   a    b

(That looks good in a fixed-width font. YMMV.)

Anyhow, the point is that the antlrworks product appears to generate an 
AST that is wrong. This is incredibly frustrating, to me and apparently 
to others. Hence the recent set of emails.

However, I was in the process of trying to see exactly what changes 
would cause the thing to break when I inadvertently ran a "make test" on 
my system, which compiled my grammar and linked it against a test jig 
that runs the grammar on an input file. I opted to try that approach, 
and got:

java org.antlr.Tool  src/hlasm/Hlasm.g
ANTLR Parser Generator  Version 3.0.1 (August 13, 2007)  1989-2007
javac -g -d classes -sourcepath src src/hlasm/Test.java
jar -cmf manifest.txt hlasm.jar -C classes .
java -jar hlasm.jar
Hello, world. Reading from input
Got lexer
Got Tokens
Got parser
Got tree
(DECL int a) (DECL int b)


Notice the interesting tree dump at the bottom? It seems that the same 
grammar produces the desired AST in plain-old-antlr, at least according 
to the tree-to-string code.
 
I don't actually know if this is a generated-tree problem, or a 
displaying-it-wrong problem. Maybe the graph drawing code is skipping 
nodes it has previously seen. Regardless, there appears to be a 
difference. This is either a bug in the Antlr debug library, or a bug in 
AntlrWorks.

The grammar is below.

=Austin

grammar Hlasm;
options { output = AST; }
tokens { DECL; INT = 'int';}
@header {
package hlasm;
import hlasm.*;
}
@lexer::header {
package hlasm;
}

compilation_unit :      decl* ;

decl:
        type=type_spec  declarator (',' declarator)* ';'
                -> ^(DECL $type declarator)+
        ;

type_spec :     INT;
declarator: ID;
ID: 'a'..'z';
WS: (' ' | '\n') { channel=HIDDEN; };