Why doesn't my keymap let-binding work?

Question

I'm trying to define the keymap for a major mode but keep getting the error: Wrong type argument: keymapp.

What am I doing wrong?

(defun insert-text ()
  (interactive)
  (let ((x (read-string "Enter text to be printed: ")))
    (insert x)))

(defvar test-mode-map
  (let ((map (make-keymap)))
    (define-key map (kbd "M-S-RET") 'insert-text)))

(defun test-mode ()
  (interactive)
  (setq major-mode 'test-mode
    mode-name  "Test Mode")
  (use-local-map test-mode-map))

I read another question with a similar error but it doesn't really help.

Answer 1

The problem is in the let-binding of your defvar form.

The let will return the value of its last form. Currently, the last form is define-key, which returns the function symbol which you bound to the keys.

Instead, you want to return the map you created:

(defvar test-mode-map
  (let ((map (make-keymap)))
    (define-key map (kbd "M-S-RET") 'insert-text)
    map))                           ; need to return the keymap

(keymapp test-mode-map)             ; => t