Can't access a global variable inside a function in elisp?

I am trying to make a simple function that toggles "lsp-ui-doc-show" and "lsp-ui-doc-hide", by calling the same function every time.

Thought it was simple enough to use a global variable, call the command and then modify the same variable from inside the function.

Here is the code:

(defvar lsp-ui-doc-toggle 1)

(defun toggle-lsp-ui-doc ()
  (interactive)
  (if (eq lsp-ui-doc-toggle 1)
      (call-interactively 'lsp-ui-doc-show)
    (set lsp-ui-doc-toggle 2)
      )
  (if (eq lsp-ui-doc-toggle 2)
      (call-interactively 'lsp-ui-doc-hide)
    (set lsp-ui-doc-toggle 1)
    )
  )

The error I receive is if: Wrong type argument: symbolp, 1. Now, I might misunderstand the error, but I believe it comes from line 4, where I'm trying to make the comparison, right?

Does that mean I can't access lsp-ui-doc-toggle inside the function? I have also tried to define the variable with setq, tried to make the comparison with equal, =, nothing works.

Can anybody please help me understand what's going on?

Edit:

I did it. I'll post the working code here, in case it will help somebody.

As Drew answered, the error came from set, but I also had other issues in my code:

1. The if condition doesn't accept multiple statements so I had to use cond instead.
2. Both if conditions were executed one after the other, because the variable was changed to 2 by the first, which allowed the second to start. I had to use a catch/throw to end the function after changing the variable in the first condition.

(defvar lspDocSwitch 1)

(defun toggleLspDoc ()
  (interactive)
  (catch 'return
    (cond ((eq lspDocSwitch 1)
       (call-interactively 'lsp-ui-doc-show)
       (setq  lspDocSwitch 2)
       (throw 'return "End function")
       )
      )
    (cond ((eq lspDocSwitch 2)
       (setq lspDocSwitch 1)
       (call-interactively 'lsp-ui-doc-hide)
       )
      )
    )
  )