[antlr-interest] Avoiding ClassCastExceptions in org.antlr.runtime.tree.BaseTree (Limitation in ANTLR v 3.1)

[Tim Halloran]

I'm using the standard Tree implementations (extending BaseTree) in
combination with a custom implementation of Tree.  The problem is that
BaseTree assumes that it is only being used with subclasses of BaseTree
despite it's implementation really not needing to make this assumption.  I
propose fixing the code to eliminate this problem.

I modified the getChild() and toStringTree() methods in BaseTree.java.  I
changed lines 56 and 297 to cast to Tree, instead of BaseTree.  For example:

    public Tree getChild(int i) {
        if ( children==null || i>=children.size() ) {
            return null;
        }
        return (Tree) children.get(i);  // line 56
    }

There might be some other places to change, but I have only encountered
problems with these.
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