Discussion: Incorporating Erlang/OTP 21 map guards in Elixir

[jfrolich]

Another use case for is_map_key

defp request(integration = %{cache: cache}, path, opts) when :erlang.is_map_key({path, opts}, cache) do

But it would be better if we can use this in the future (compiling to guard calls perhaps?)

defp request(integration = %{cache: %{{path, opts} => cache}}, path, opts) do

[Eiji]

@josevalim

For now, we will go with extending defguard/1 (discussion #2) and adding the is_struct and is_exception guards. For the remaining ones, we will wait until more use cases arrive, if ever.

Does those plans changed or they would be realized in next releases?

I can see that is_struct (for now only /1 is added and /2 would be on next release, but there is no is_exception and your example code:

@josevalim

defguard is_drinking_age(%User{age: age}) when age >= 21

def serve_drinks(user) when is_drinking_age(user)

also is not yet supported as of 1.10.2 version.

[josevalim]

We are going with #1 and #3, we won’t add #2. is_exception was not implemented but a PR is welcome.