Why does SLY needs it own completion commands?

[kresdjan]

I don't quite understand the need for this? Why not use the builtin Emacs completion? I don't see the benefit in having to "learn" or adapt a new behaviour for one package, completions are a set and forget kind of thing.

[joaotavora]

I don't quite understand the need for this?

Am I going to answer a question you are asking yourself?

Doesn't SLY work with Emacs built-in completion? What completion commands are you talking about? What exactly do you think you have to learn?

[aadcg]

@kresdjan are you sure you studied SLY well enough? One of the areas where it shines is precisely in how it leverages Emacs' internals (including completion).