Here is an example illustrating the scope of bound declarations.
(let ((x 1)) ;[1] 1st occurrence of x
(declare (special x)) ;[2] 2nd occurrence of x
(let ((x 2)) ;[3] 3rd occurrence of x
(let ((old-x x) ;[4] 4th occurrence of x
(x 3)) ;[5] 5th occurrence of x
(declare (special x)) ;[6] 6th occurrence of x
(list old-x x)))) ;[7] 7th occurrence of x
⇒ (2 3)
The first occurrence of x establishes a dynamic binding
of x because of the special declaration for x
in the second line. The third occurrence of x establishes a
lexical binding of x (because there is no special
declaration in the corresponding let form).
The fourth occurrence of x x is a reference to the
lexical binding of x established in the third line.
The fifth occurrence of x establishes a dynamic binding
of x for the body of the let form that begins on
that line because of the special declaration for x
in the sixth line. The reference to x in the fourth line is not
affected by the special declaration in the sixth line
because that reference is not within the "would-be lexical scope"
of the variable x in the fifth line. The reference to x
in the seventh line is a reference to the dynamic binding of x
established in the fifth line.
Here is another example, to illustrate the scope of a free declaration. In the following:
(lambda (&optional (x (foo 1))) ;[1]
(declare (notinline foo)) ;[2]
(foo x)) ;[3]
the call to foo in the first line might be
compiled inline even though the call to foo in
the third line must not be. This is because
the notinline declaration
for foo in the second line applies only to the body on the
third line. In order to suppress inlining for both calls,
one might write:
(locally (declare (notinline foo)) ;[1]
(lambda (&optional (x (foo 1))) ;[2]
(foo x))) ;[3]
or, alternatively:
(lambda (&optional ;[1]
(x (locally (declare (notinline foo)) ;[2]
(foo 1)))) ;[3]
(declare (notinline foo)) ;[4]
(foo x)) ;[5]
Finally, here is an example that shows the scope of declarations in an iteration form.
(let ((x 1)) ;[1]
(declare (special x)) ;[2]
(let ((x 2)) ;[3]
(dotimes (i x x) ;[4]
(declare (special x))))) ;[5]
⇒ 1
In this example, the first reference to x on the fourth line is to
the lexical binding of x established on the third line.
However, the second occurrence of x on the fourth line lies within
the scope of the free declaration on the fifth line
(because this is the result-form of the dotimes)
and therefore refers to the dynamic binding of x.