Inline function at specific use site

[Anrock]

I've noticed that quite often when refactoring code it ends up with some function being used only in one place or body of a function being simplified so it no longer makes sense to have it separate. For both cases I usually inline a function which is completely mechanical process, thanks to referential transparency in Haskell.

Could we have a "inline function" code action which will basically just replaces function application with function's body?

[Ailrun]

I believe retrie plugin already supports similar feature under the name Unfold _.

[Anrock]

Hm, not sure how to invoke it then.
Given

foo :: Integer
foo = bar 2

bar :: Num a => a -> a
bar x = x * 2

Hovering over bar in foo body lists no code actions at all.

Edit: hovering over bar definitions indeed provides unfold action, but it unfolds bar everywhere. I guess I want unfold to be invokable at application site and unfolding only at this site instead of whole project / file.

[michaelpj]

The UX is a little awkward here: we probably don't want to provide a code action for every identifier in the file saying "inline this". Or maybe we do? I'm not sure.

(Note that retrie can also expand type synonyms so this applies to them too)

[pepeiborra]

Isn't this already available in the HLS-retrie-plugin? I added it a few months ago.
Note that it only exposes the underlying retrie functionality, which is limited (e.y functions defined via multiple equations cannot be inlined) and buggy in ghc 9.x

[michaelpj]

It does seem to be there indeed! Although I can't get it to show up for type synonyms, only functions?