[erlang-questions] Dialyzer

Carlo Bertoldi <>
Mon May 2 12:11:30 CEST 2011

On 02/05/2011 11:55, Kostis Sagonas wrote:
> Carlo Bertoldi wrote:
>> On 02/05/2011 11:23, Kostis Sagonas wrote:
>>> Carlo Bertoldi wrote:
>>>> Hello list,
>>>>  this is a bad monday, and I'm stuck with this warning from dialyzer:
>>>> The specification for change_interval/2 states that the function 
>>>> might also return [any()] but the inferred return is none()
>>>> The code:
>>>> -spec(change_interval(integer(), [term()]) -> [term()]).
>>>> change_interval(NewInterval, Config) ->
>>>>     NewPause = {pause, NewInterval},
>>>>     NewConfig = lists:keyreplace(pause, 1, Config, NewPause),
>>>>     write_config(NewPause),
>>>>     NewConfig.
>> I apologize for the incompleteness, here goes the module
> Well, probably it's a bad Monday alright for you.  Wondering what 
> exactly it is you did during the weekend... ;)
You don't wanna know ;)
> Anyway, didn't you happen to notice that dialyzer generates an awful 
> lot of other warnings for this module? 
Actually yes, but I thought about resolving the first issue of the list 
Of course I was awfully wrong, after fixing the call to file:open, all 
the other warnings disappeared in a puff of logic.
This is a silly error indeed, but I wonder, how come that write_config 
was working anyway?
I tested that before the weekend ;)
> Among them, a warning that basically tells you that the proper way to 
> use file:open/2 is with a list of options in the second argument, i.e. 
> file:open(File, [write]), instead of what you've written below?  
> Please fix this.
> As to the warning you are getting, can't you see that the function 
> change_interval/2 is nowhere used in this file?  Even erlc will tell 
> you that.
Sorry again, I didn't paste every lines of the actual module, and I've 
read the mail a couple of times. Guess I do need a triple coffee.


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