Dialyzer complaining about function head not matching, when subsequent head should

Questions & Help Questions
1

I’m getting a dialyzer error and I don’t understand why.

lib/conduit/plug/retry.ex:74:pattern_match
The pattern
:nack, _, _wait_time

can never match the type
%{:__exception__ => true, :__struct__ => atom(), atom() => _}, _, integer()

The code it’s complaining about is here:
https://github.com/conduitframework/conduit/blob/master/lib/conduit/plug/retry.ex#L74-L85

It is true, that particular function head will not match, but the one following that should match that pattern fine.

2

This is basically what dialyzer is telling you. It is saying that that particular clause of the log_error/3 function will never match as it will never be called with the first argument as :nack. It is not complaining about the function as a whole.

Yes, sometimes dialyzer warnings can be a bit cryptic to understand. :wink: It is generally trying to work both ways with functions and match a definition of a function and the calls to it and check if they work. It uses something called Success typing.

3

Thanks, it appears I was calling a function with one too few arguments.

https://github.com/conduitframework/conduit/commit/8e3d9a681f7b90a102d14a86e7d415fd15c05acb