This package highlight the location where local variables is
created (bound, for example by `let') as well as quoted and
backquoted constant expressions.

Example:

Below, `^' is used indicate highlighted normal variables and
constant expressions. `*' is used to show highlighting of special
variables (i.e. those defined by `defvar') and of the backquote and
comma operators.

(defun my-function (next)
                    ^^^^             <- Parameters
  (let ((numbers '(one two three))
         ^^^^^^^  ^^^^^^^^^^^^^^^    <- Var bound by `let' and quoted expr.
        (buffer-read-only t))
         ****************            <- Special variable (different color)
    `(,@numbers and ,next)))
    *^**        ^^^ *    ^           <- Backquote and comma

Screenshot:

![See doc/demo.png for screenshot](doc/demo.png)

What is highlighted:

* Parameters in functions and lambdas

* Variables bound by specal constructs like `let', `dolist',
  `condition-case', and `pcase-let'

* Normal variables and variables declared as globals using `defvar'
  are highlighted in different colors, as a warning

* Quoted expressions

* Backquoted expressions. Subexpressions using the "," or ",@" are
  not highlighted (as they are evaluted and thus not constant).
  Also, the backquote and the comma operators themselves are
  highlighted using a bright color as a warning.

* Hash-quoted symbols.

Installation:

Place this package in a directory in the load-path. To activate it,
use *customize* or place the following lines in a suitable init
file:

   (require 'lisp-extra-font-lock)
   (lisp-extra-font-lock-global-mode 1)

Customization:

You can modify the following lists to add more functions that are
recognized:

* `lisp-extra-font-lock-let-functions' -- List of function with the
  same syntax as `let'

* `lisp-extra-font-lock-defun-functions' -- List of function with
  the same syntax as `defun'

* `lisp-extra-font-lock-lambda-functions' -- List of function with
  the same syntax as `lambda'

* `lisp-extra-font-lock-dolist-functions' -- List of function with
  the same syntax as `dolist'

* `lisp-extra-font-lock-bind-first-functions' -- List of function
  that bind their first argument, like `condition-case'.

* `lisp-extra-font-lock-loop-functions' -- List of functions with
  the same syntax as `cl-loop'.

The following faces are used when highlighting. You can either
redefine the face (e.g. using a theme), or you can rebind the
corresponding variable.

* Local variables are highlighted using the standard face
  `font-lock-variable-name-face'

* Special (global) variables that are rebound are highlighted using
  the face bound to the variable
  `lisp-extra-font-lock-special-variable-name-face' (by default
  `lisp-extra-font-lock-special-variable-name', which inherits from
  `font-lock-warning-face')

* Quoted expressions use the face bound to the variable
  `lisp-extra-font-lock-quoted-face' (by default
  `lisp-extra-font-lock-quoted', which inherits from
  `font-lock-constant-face')

* The backquote and comma operators use the face bound to the
  variable `lisp-extra-font-lock-backquote-face' (by default
  `lisp-extra-font-lock-backquote', which inherits from
  `font-lock-warning-face').

* Named arguments to `cl-loop' are highlighted using
  `font-lock-builtin-face'.

Example:

To set the face used to highlight quoted expressions to a gray
color, you can use:

    (custom-set-faces
      '(lisp-extra-font-lock-quoted ((t :foreground "grey50"))))