bug#34757: Invalid bytecode from byte compiler

[Eli Zaretskii]

> From: chuntaro <chuntaro@sakura-games.jp>
> Date: Tue, 5 Mar 2019 17:01:00 +0900
> 
> Invalid bytecode is output and error occurs when executed.
> 
> Byte compile the following code.
> 
> bug.el
> ----------------------------------------------------------------
> ;;; -*- lexical-binding: t; -*-
> 
> (let ((a 2))
>   (print 1)
>   (setq a 1))
> ----------------------------------------------------------------
> 
> $ emacs --batch -f batch-byte-compile bug.el
> 
> bug.elc
> ----------------------------------------------------------------
> ;ELC
> ...
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> 
> 
> (funcall 2 'print 1)
> 1
> ----------------------------------------------------------------
> 
> $ emacs --batch -l bug.elc
> Invalid function: 2

Why is that a problem?  The Lisp code is invalid, and the error
message says that much.