Hello everyone,
dialyzer and I are fighting again Ok so I’ve got the following code:
defimpl DeepMerge.Resolver, for: Any do
def resolve(original = %{__struct__: struct}, override = %{__struct__: struct}, resolver) do
implementors = get_implementors(DeepMerge.Resolver.__protocol__(:impls))
if Enum.member?(implementors, struct) do
Map.merge(original, override, resolver)
else
override
end
end
def resolve(_original, override, _fun), do: override
defp get_implementors({:consolidated, implementors}), do: implementors
defp get_implementors(:not_consolidated) do
IO.warn "Protocols not consolidated and trying to merge two structs of the same type. Not supported!"
# let the code work with override semantics without being intrusive
[]
end
end
This is for my deep_merge library, trying to provide a default derivable behaviour while keeping fallback_to_any in place (which I need). You can check out & play with the real code in this PR.
The warning dialyzer gives me is:
lib/deep_merge/resolver.ex:95:pattern_match
The pattern
{:consolidated, _implementors}
can never match the type
:not_consolidated
Which I don’t understand because unless I have been having a gross typo for the last 30+ minutes then I am matching on :not_consolidated
.
I’m thinking dialyzer might be confused because the elixir definition is:
@spec __protocol__(:impls) :: :not_consolidated | {:consolidated, [module]}
Kernel.def(__protocol__(:impls), do: :not_consolidated)
Where it’s success typing might end up as "this is always :not_consolidated
"
Removing the clause with {:consolidated, implementors}
funnily enough removes the dialyzer error but makes my tests fail
Is there anything I can do in my setup/code that isn’t just configuring dialyxir to ignore the error?