Ah it has both actions “Type annotate” and upcoming “Remove type annotation”! I wasn’t aware. I could maybe retire this extension. Except, it enhances the functionality for selections – it annotates multiple let-bindings at once. The code action treats a selection as indicating the expression to annotate.
I have take a look into your solution, which is related to my current work.
I’ve been working on improving type annotations in ocaml-lsp. The problem with functions is actually a bit harder then I expected, so for now it will probably be disabled. You can find the discussion and explanation here: