"tcfail016.hs", line 8:
    Couldn't match type "(a, Expr a)" against "Expr a".
    Inside a function binding:
	g ... (Var name)
		      = [name]
	      (App e1 e2)
		      = (g e1) ++ (g e2)
Fail: Compilation errors found

ghc: execution of the Haskell compiler had trouble