The elm-review rule NoCatchAllForSpecificRemainingPatterns.rule enforces that all specific cases are listed if possible.

Below would be reported for example

type Resource
    = Loaded String
    | FailedToLoad String
    | Loading

displayResource : Resource -> String
displayResource resource =
    case resource of
        Loaded text ->
            Ui.text text
        
        _ ->
            Ui.spinner

Try it:

elm-review --template lue-bird/elm-review-no-catch-all-for-specific-remaining-patterns/example

If you like it, add it, add it to your configuration

module ReviewConfig exposing (config)

import NoCatchAllForSpecificRemainingPatterns
import Review.Rule exposing (Rule)

config : List Rule
config =
    [ NoCatchAllForSpecificRemainingPatterns.rule
    ]

why?

• no accidentally missed cases:

  patternIsZero expression =
      case expression of
          Elm.Syntax.Pattern.IntPattern int ->
              int == 0
          
          _ ->
              -- accidentally missed HexPattern!
              False

• a reminder if another variant is added in the future:

  type Resource
      = Loaded String
      | FailedToLoad String
      | Loading
      -- added
      | PartiallyLoaded String
  
  displayResource : Resource -> String
  displayResource resource =
      case resource of
          Loaded text ->
              Ui.text text
          
          _ ->
              -- we actually should display partially loaded
              -- but the compiler doesn't remind us
              Ui.spinner

• less jumping around to understand the code

  case result of
      Ok geoLocation ->
          let
              ...
          in
          a
              bunchOf
              code
  
      _ ->
          -- what is _ ?
          0

not implemented (yet?)

• nested patterns like in tuples, variants or lists