csi> (define foo (case-lambda (() 'bar) ((bar #!optional baz) baz)))
csi> (foo)
bar
csi> (foo 1)

Error: no matching clause in call to 'case-lambda' form

        Call history:

        <syntax>          (foo 1)
        <eval>    (foo 1)
        <eval>    [foo] (length rvar79)
        <eval>    [foo] (eq?82 lvar80 0)
        <eval>    [foo] (eq?82 lvar80 3)
        <eval>    [foo] (##sys#error (##core#immutable (quote "no matching clause in call to 'case-lambda' form")))     <--