public String getDocComment(Element e) {
        // Our doc comment is contained in a map in our toplevel,
        // indexed by our tree.  Find our enter environment, which gives
        // us our toplevel.  It also gives us a tree that contains our
        // tree:  walk it to find our tree.  This is painful.
        Pair<JCTree, JCCompilationUnit> treeTop = getTreeAndTopLevel(e);
        if (treeTop == null)
            return null;
        JCTree tree = treeTop.fst;
        JCCompilationUnit toplevel = treeTop.snd;
        if (toplevel.docComments == null)
            return null;
        return toplevel.docComments.get(tree);
    }