lib/shrink.js
function(xts) {
    return new RoseTree(
      xts.map(function(tree) { return tree.root; }),
      function() {
        return exports.array(xts, tryRemoving);
      }
    );
  }
function(xts) {
    return new RoseTree(
      xts.map(function(tree) { return tree.root; }),
      function() {
        return exports.array(xts, tryRemoving);
      }
    );
  }
xtreesToArray :: [RoseTree a] -> RoseTree [a] FIXME: This is duplication of code in types.arrayOf.