Since OCaml's emacs mode is not able to make sense of cmt[i] files I was experimenting with ocp-index's C-c t to show the type at point. The feature seems very buggy. On the following file:

let x = 3
let f x =
  let y = "bla" in
  x, y

module M = struct
  let z = 3
end

• The first x correctly says int
• The f correctly says 'a -> 'a * string
• Both x in the definition of f incorrectly say int
• Both y in the definition of f say No definition found
• "bla" says No definition found
• z says No definition found