tcfail016.hs:9: Couldn't match the type `Expr' against `(,) taUk'
    Expected: `AnnExpr taUk'
    Inferred: `Expr taUk'
    In the first argument of `g', namely `e1'
    In the first argument of `++', namely `(g e1)'
    In an equation for function `g': `g (App e1 e2) = (g e1) ++ (g e2)'

Compilation had errors