bug#64272: 28.1; lisp_file_lexically_bound_p behavior mismatches file local variables

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 24 Jun 2023 13:22:38 -0500
> From: LdBeth <andpuke@foxmail.com>
> 
> 
> Basically, if an emacs lisp source file starts with some whitespace
> 
> | ;; -*- lexical-binding: t -*-
> |(let ((x 1)) (setq foo (lambda () x)))
> |(funcall foo)
> 
> rather than
> 
> |;; -*- lexical-binding: t -*-
> |(let ((x 1)) (setq foo (lambda () x)))
> |(funcall foo)
> 
> that will cause `load' eval the file with `lexical-binding' set to nil,
> and would report `x' is a void variable.
> 
> This behavior is in contrast to how file local variables are applied
> when opening a file, that is, as long as the variable list is in
> the first line, it is applied.
> 
> Either the documentation should bring up this behavior, or the
> C function `lisp_file_lexically_bound_p' in `src/lread.c' should be fixed.

I think we should do the latter, because
hack-local-variables-prop-line is more lenient than
lisp_file_lexically_bound_p.

Stefan, any comments?