Dict.toList >> List.map with lambda ignoring tuple element

[jfmengels]

someDict
  |> Dict.toList
  |> List.map (\( k, _ ) -> f k)
-->
someDict
  |> Dict.keys
  |> List.map (\k -> f k)

We already have a check to see if the argument to List.map is Tuple.first (or a lambda equivalent). I think we should maybe (instead, or in addition to) check whether the second part of the tuple gets ignored.

someDict
  |> Dict.toList
  |> List.map Tuple.first
-->
someDict
  |> Dict.keys
  |> List.map identity -- will get simplified afterwards

someDict
  |> Dict.toList
  |> List.map (\( k, _ ) -> f k)
-->
someDict
  |> Dict.keys
  |> List.map (\k -> f k)

Same for Tuple.second.