some-old-comp.el

(defun check-expansion ()
  (save-excursion
    (cond ((looking-at "\\_>") t)
          ((unless (bobp) (backward-char 1) (looking-at "\\.")) t)
          ((unless (bobp) (backward-char 1) (looking-at "->")) t)
          (t nil))))

(defun smart-tab (&optional prefix)
  "This smart tab is minibuffer compliant: it acts as usual in
  the minibuffer. Else, if mark is active, indents region. Else if
  point is at the end of a symbol, expands it. Else indents the
  current line."
  (interactive "P")
  (cond ((minibufferp)
         (unless (minibuffer-complete)
           (dabbrev-expand nil)))
        ((use-region-p) ;mark-active
         (indent-region (region-beginning)
                        (region-end)))
        ((check-expansion) (hippie-expand prefix))
        ((indent-for-tab-command))))

(defun tab-indent-or-complete (&optional prefix)
  (interactive "P")
  (cond ((minibufferp)
         (unless (minibuffer-complete) (dabbrev-expand nil)))
        ((and yas-minor-mode
              (let ((yas-fallback-behavior 'return-nil))
                (yas-expand))))
        ((and (check-expansion) (company-complete-common)))
        ((indent-for-tab-command))))

(global-set-key [?\t] #'tab-indent-or-complete)