Inconsistant equality for objects containing NaN

[harrysarson]

If two (different) identical objects contains NaN the full structured equality finds them to be different.

However, if an object containing NaN is compared with itself the shortcut reference equality means that the (==) operator returns true.

The following also works with records, union types, etc as well as lists.

SSCCE (https://ellie-app.com/3jTfFrpjNbJa1)

module Main exposing (main)

import Html exposing (Html, button, div, text)


nan1 = [ 0/0 ]

nan2 = [ 0/0 ]

main : Html never
main =
    div 
        []
        [ div [] [ text <| "nan1 == nan1 -- " ++ (Debug.toString (nan1 == nan1)) ]
        , div [] [ text <| "nan1 == nan2 -- " ++ (Debug.toString (nan1 == nan2)) ]
        ]

Output

nan1 == nan1 -- True
nan1 == nan2 -- False

Problem

The result is inconsistent. Both equalities should either evaluate as True or False and be consistent with each other.