Changing opaque type to type alias results in MAJOR bump

[gampleman]

module Foo exposing (Foo)

type Foo =
     Foo Int

Gets changed to

module Foo exposing (Foo)

import Internal

type alias Foo =
     Internal.Foo

module Internal exposing (Foo)

type Foo =
     Foo Int

where Internal is not in "exposed-modules". Conceptually, this doesn't change anything for the calling code of this package, as it is still the same type, just it's implementation details changed slightly (but being able to do that was the point of making it opaque in the first place). As such, this should be a PATCH change.

However, elm diff gives:

---- Foo - MAJOR ----

    Added:
        type alias Foo =
            Internal.Foo 

    Removed:
        type Foo

• Elm: 0.19
• Operating System: OSX 10.14.3

[drathier]

Changing the custom type to a type alias essentially exposes a constructor to it, so it makes sense the way it is now. Recusing down the types to figure out if it's possible to actually construct that type alias is probably quite a lot of effort.

[harrysarson]

Changing the custom type to a type alias essentially exposes a constructor to it

In which case should this be a MINOR change, equivalent to adding a new function?

[gampleman]

I don’t believe this is true: the constructor is not exposed in either scenario.