An Elm Error: declaring a type equal to another doesn't make sense

compile-results.txt

## ERRORS in Failure.elm #######################################################

-- TYPE MISMATCH --------------------------------------------------- Failure.elm

The type annotation for `update` does not match its definition.

17| update: Action -> Model -> Model
            ^^^^^^^^^^^^^^^^^^^^^^^^
As I infer the type of values flowing through your program, I see a conflict
between these two types:

    InnerModel

    InnerComponent.Model


-- TYPE MISMATCH --------------------------------------------------- Failure.elm

The 1st argument to function `update` has an unexpected type.

20|                                   InnerComponent.update ia m.inner
                                                            ^^
As I infer the type of values flowing through your program, I see a conflict
between these two types:

    InnerComponent.Action

    InnerAction

Failure.elm

module Failure where

import InnerComponent

--- ACTION
type InnerAction = InnerComponent.Action -- oops, meant type alias

type Action = Passthru InnerAction

-- MODEL
type InnerModel = InnerComponent.Model -- oops, meant type alias

type alias Model = { inner: InnerModel }

--- UPDATE

update: Action -> Model -> Model
update a m =
  case a of
    Passthru ia -> { m | inner <- InnerComponent.update ia m.inner }

InnerComponent.elm

module InnerComponent(update, Action, Model) where

type Action = Something String | Else

type alias Model = { something: String }

update: Action -> Model -> Model
update a m = m