A simple protocol yields two kinds of dialyzer warnings:
defmodule Dtest do
defprotocol Valid do
@doc "Returns true if data is in a valid state"
def valid?(data)
end
defimpl Valid, for: Integer do
def valid?(_), do: true
end
end
The warning I can't figure out is this:
dtest.ex:2: The specification for
'Elixir.Dtest.Valid':'__protocol__'/1 states that the function might
also return 'true' but the inferred return is
'Elixir.Dtest.Valid' | 'false' | [{'valid?',1},...]
I also couldn't figure out a @spec that'd work here to silence the warning.
The other kind of warning has been discussed elsewhere – many "unknown functions" listed:
Unknown functions:
'Elixir.Dtest.Valid.Atom':'__impl__'/1
'Elixir.Dtest.Valid.BitString':'__impl__'/1
(etc.)
Is there a @spec that can be used with defprotocol's? I haven't found any examples. Or, is there a way, in the source code to mark the defprotocol to be ignored by dialyzer?
EDIT: Here's the full fix for the first error:
defmodule Dtest do
defprotocol Valid do
@doc "Returns true if data is in a valid state"
@dialyzer {:nowarn_function, __protocol__: 1}
def valid?(data)
end
defimpl Valid, for: Integer do
def valid?(_), do: true
end
end
