Why isn't `badargs` used more helpfully?

It’s typical to see this when programming in Elixir:

** (ArgumentError) argument error

Which can originate when a function calls:

erlang:error(badarg, SomeVariable).

But this isn’t very useful. If you’ve called a function with 4 arguments then you’re left guessing which one was wrong.

Instead of passing the symbol badarg you can pass a tuple.

some_variable = 3
:erlang.error({:badarg, some_variable})

Which actually passes along the given value in the error output.

** (ArgumentError) argument error: 3

But that functionality is undocumented, :badarg is listed by itself, not as a tuple in the documented exit reasons.

The telemetry library calls the error function with just :badarg and it’s a not clear that you have to pass a list rather than just a symbol to the attach function, https://github.com/beam-telemetry/telemetry/blob/master/src/telemetry.erl#L193.

It would be nice to change this error to be more informative in this library but I’m confused about what’s idiomatic or allowed for badargs in Erlang.