Type checking of protocol dispatch

[josevalim]

We now type check arguments given to a protocol. The following code:

defmodule HelloWorld do
  def example() do
    to_string(1..3)
  end
end

emits this warning:

We specially handle string interpolations to provide a better experience. So if we replace to_string(1..3) by "#{1..3}", we will this warning instead:

TODO

• Unit tests of protocol consolidation with and without fallback
• Unit tests of protocol consolidation without implementations
• Integration tests of interpolation
• Integration tests of protocol dispatch
• Improve warnings for mismatched implementations

[whatyouhide]

Should we suggest for which type to implement this?

[josevalim]

Unfortunately no, because there may be an infinite amount of them. If someone has a type of not Range.t, it can be any other struct, which wouldn't be valid in String.Chars (and some structs definitely do not implemnt String.Chars , but we also cannot list them).

[whatyouhide]

Would maps:from_list/1 here make this code easier to read, so that we don't need to do the mental math to check that the fields below are ordered? 😬