[erlang-questions] 12B4 dialyzer problem 5

Anthony Shipman <>
Wed Sep 17 16:23:23 CEST 2008

I had a -spec that read

-spec getHandlerModule(string()) -> {ok, Module::atom(), StrmID::integer} | 

This caused code like

    case getHandlerModule(HName) of
    {ok, Mod, DefaultID} ->
	OptionMeta = Mod:optionMetadata(),
	checkForm(Sess, Arg, OptionMeta, createStream4(DefaultID, HName));
    error ->

to result in the dialyzer message
    The pattern {'ok', Mod, DefaultID} can never match the type 'error'

I can see where my typo is but I can't relate it the error message. I would 
expect that the pattern will always match and I'd get a type error further 
Anthony Shipman                    Mamas don't let your babies 
                   grow up to be outsourced.

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