My imenu config for scala.

gistfile1.el

;; M-x package-install imenu-anywhere

(add-hook 'scala-mode-hook
          (lambda ()
            (setq imenu-generic-expression
                  '(
                    ("var" "\\(var +\\)\\([^(): ]+\\)" 2)
                    ("val" "\\(val +\\)\\([^(): ]+\\)" 2)
                    ("override def" "^[ \\t]*\\(override\\) +\\(def +\\)\\([^(): ]+\\)" 3)
                    ("private def" "^[ \\t]*\\(private\\(\\[.*?\\]+\\)*\\) +\\(def +\\)\\([^(): ]+\\)" 4)
                    ("protected def" "^[ \\t]*\\(protected\\(\\[.*?\\]+\\)*\\) +\\(def +\\)\\([^(): ]+\\)" 4)
                    ("implicit def" "^[ \\t]*\\(implicit\\) +\\(def +\\)\\([^(): ]+\\)" 3)
                    ("def" "^[ \\t]*\\(def +\\)\\([^(): ]+\\)" 2)
                    ("trait" "\\(trait +\\)\\([^(): ]+\\)" 2)
                    ("class" "^[ \\t]*\\(class +\\)\\([^(): ]+\\)" 2)
                    ("case class" "^[ \\t]*\\(case class +\\)\\([^(): ]+\\)" 2)
                    ("abstract class" "^[ \\t]*\\(abstract class +\\)\\([^(): ]+\\)" 2)
                    ("object" "\\(object +\\)\\([^(): ]+\\)" 2)
                    ))))
                    

;; add Control-. so you can find stuff via imenu-anywhere
(global-set-key (kbd "C-.") 'imenu-anywhere)

;; Puts the current imenu thing in top line of the buffer.
(which-function-mode)
(setq-default header-line-format
              '((which-func-mode ("" which-func-format " "))))
(setq mode-line-misc-info
      ;; We remove Which Function Mode from the mode line, because it's mostly
      ;; invisible here anyway.
      (assq-delete-all 'which-func-mode mode-line-misc-info))

(setq which-func-unknown "n/a")