`type alias A a = a` should unify with `a`

[aforemny]

Quick Summary: type alias A a = a, A a should unify with a.

SSCCE

type alias A a = a

a : a -> A a
a = identity

• Elm: 0.19.1
• Browser: N/A
• Operating System: NixOS 23.05pre-git (Stoat)

Additional Details

This arose as I wanted to eliminate Node from stil4m/elm-syntax for an experiment. elm-syntax' Node is a custom type that occurs across a variety of records in a variety of files. Instead of changing all those records in all those files, I figured it'd be easier to define type alias Node a = a and only fix the single Elm.Syntax.Node module.

[github-actions[bot]]

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[lue-bird]

Another example of the same bug https://github.com/elm/compiler/issues/2252