Inconsistent types comparisons between records built from extensible records aliases

[rlefevre]

Quick Summary:
There are some inconsistencies when comparing records types and records types built from extensible record aliases.

SSCCE

module Bug exposing (x, y, z)

import Html exposing (Html)


type alias Named a = { a | name : String }


x : Named { name : String }
x = { name = "" }


y : Named {}
y = { name = "" }


z : { name : String }
z = { name = "" }

Then in elm repl:

> import Bug exposing (..)

> x == z
True : Bool

> y == z
True : Bool

> x == y
-- TYPE MISMATCH ---------------------------------------------------------- REPL

I need both sides of (==) to be the same type:

4|   x == y
     ^^^^^^
The left side of (==) is:

    Named { name : String }

But the right side is:

    Named {}

Different types can never be equal though! Which side is messed up?

• Elm: 0.19.1
• Browser: Any
• Operating System: Any

Additional Details

Related to #2071.

Thank you to @jacobkoling for reporting the issue on Discourse:
https://discourse.elm-lang.org/t/compiler-trips-up-on-extensible-records/5623

[github-actions]

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