[antlr-interest] Problem compiling trivial Tree Pattern Matcher grammar

[Jonathan Claggett]

Hello all,

Has anyone successfully used the filter=true option in a tree grammar file?
I'm running into the following pair of Java errors when I try to compile the
generated java:

topdown() in Test cannot override topdown() in
org.antlr.runtime.tree.TreeRewriter; attempting to use incompatible return
type
        found   : Test.topdown_return
        required: java.lang.Object
bottomup() in Test cannot override bottomup() in
org.antlr.runtime.tree.TreeRewriter; attempting to use incompatible return
type
        found   : Test.bottomup_return
        required: java.lang.Object


I'm using Antlr 3.3, my target language is Java (I guess that's obvious) and
my build tool is Maven. Finally, the full tree grammar is:

tree grammar Test;
options {
    ASTLabelType=CommonTree;
    output=AST;
    filter=true;
}
topdown : ;
bottomup: ;


I'm getting the same errors with my real, more complex tree grammar files
too but I'm obviously doing something wrong.

Thanks for the help,
Jonathan