Fix (length NON-SEQUENCE) documentation

Suggested by Eli Zaretskii <eliz@gnu.org> in the following threads:
https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00171.html
https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00206.html

* doc/lispref/sequences.texi (Sequence Functions): Mention that
'length' signals a 'wrong-type-argument' also when given a
non-sequencep argument.

1 files changed, 7 insertions, 5 deletions

diff --git a/doc/lispref/sequences.texi b/doc/lispref/sequences.texi
index 59faf2b4f1e..188a3451140 100644
--- a/doc/lispref/sequences.texi
+++ b/doc/lispref/sequences.texi
@@ -71,13 +71,15 @@ string, bool-vector, or char-table, @code{nil} otherwise.
 @cindex list length
 @cindex vector length
 @cindex sequence length
+@cindex bool-vector length
 @cindex char-table length
 @anchor{Definition of length}
-This function returns the number of elements in @var{sequence}.  If
-@var{sequence} is a dotted list, a @code{wrong-type-argument} error is
-signaled; if it is a circular list, a @code{circular-list} error is
-signaled.  For a char-table, the value returned is always one more
-than the maximum Emacs character code.
+This function returns the number of elements in @var{sequence}.  The
+function signals the @code{wrong-type-argument} error if the argument
+is not a sequence or is a dotted list; it signals the
+@code{circular-list} error if the argument is a circular list.  For a
+char-table, the value returned is always one more than the maximum
+Emacs character code.
 
 @xref{Definition of safe-length}, for the related function @code{safe-length}.