T5892a.hs:12:8: Warning:
    Fields of ‘Node’ not initialised: Data.Tree.subForest
    In the expression: Node {..}
    In the expression: let rootLabel = [] in Node {..}
    In an equation for ‘foo’:
        foo (Node {..}) = let rootLabel = ... in Node {..}

<no location info>: 
Failing due to -Werror.