Aliases in function type annotations change the generated code

[tesk9]

When a function uses a type alias in its annotation, the generated code will use an Expression rather than the actual type.

That is, if I have a function

{-| -}
fWithoutAlias : { a : List Int } -> ()
fWithoutAlias _ =
    ()

The generated code will have the type annotation: fWithoutAlias : { a : List Int } -> Elm.Expression

but if my starting function is identical except that it uses an alias:

type alias Config =
    { a : List Int }


{-| -}
fWithAlias : Config -> ()
fWithAlias _ =
    ()

the generated code will have the type annotation fWithAlias : Elm.Expression -> Elm.Expression.

I expected the generated code to be same whether or not I referenced a type alias in the function signature.

[tesk9]

Just for clarity: what I'm trying to do is follow the UsingHelpers guide to generate code that works with published packages. I'm using code from the Gen namespace, not the code that ends up in the generated folder.