Your type "Players" is recursive in a way you almost certainly did not intend.
That's what leads to this mismatch.
> Am 16.09.2016 um 04:09 schrieb Mohammad Samman <moes...@gmail.com>:
>
> I have the following elm code:
>
> import Json.Decode as Json exposing(..)
> import Result
>
> type Players = Players (List Players)
> type alias Player = {
> name: String
> , team: Maybe Team
> }
>
> type alias Team = {
> name: String
> , players: Maybe Players
> }
>
> teamDecoder: Json.Decoder Team
> teamDecoder =
> Json.object2 Team ("name" := Json.string) (Json.maybe ("players" :=
> playersDecoder))
>
> playersDecoder: Json.Decoder Players
> playersDecoder =
> Json.customDecoder (Json.list playerDecoder) (\pl ->
> Result.Ok (Players pl)
> )
>
> playerDecoder: Json.Decoder Player
> playerDecoder =
> Json.object2 Player ("name" := Json.string) (Json.maybe ("team" :=
> teamDecoder))
>
> Compiling give me the following error
>
> -- TYPE MISMATCH
> ---------------------------------------------------------------
> The 2nd argument to function `customDecoder` is causing a mismatch.
> 26|> Json.customDecoder (Json.list playerDecoder) (\pl ->
> 27|> Result.Ok (Players pl)
> Function `customDecoder` is expecting the 2nd argument to be:
> List { name : String, team : Maybe Team } -> Result String a
> But it is:
> List Players -> Result a Players
> Hint: I always figure out the type of arguments from left to right. If an
> argument is acceptable when I check it, I assume it is "correct" in subsequent
> checks. So the problem may actually be in how previous arguments interact with
> the 2nd.
>
> I'm wondering why this is the case? Shouldn't the pl variable inside of the
> anon func be a List Players based on the type signature of
> Json.customDecoder? How can I decode into the Team type alias?
>
> Thanks!
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