(defvar-local is-new-file-buffer nil)

(defun save-new-file-before-kill ()
  (when (and (not (buffer-file-name))
             is-new-file-buffer
             (yes-or-no-p
              "New file has not been saved. Would you like to save before closing?"))
    (call-interactively 'save-buffer)))

(add-hook 'kill-buffer-hook 'save-new-file-before-kill)

(defun new-file (dir)
  (interactive "DCreate New File In: ")
  (let ((buffer (generate-new-buffer "<Unsaved File>")))
    (switch-to-buffer buffer)
    (setq-local default-directory dir)
    (setq-local is-new-file-buffer t)))

(globoal-set-key [(f12)] 'new-file)

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