deprecate passing a number as the destination to `format'

* module/ice-9/format.scm (format): Deprecate having a number as the
  destination.
* doc/ref/misc-modules.texi (Formatted Output): Update docs.

2 files changed, 8 insertions, 5 deletions

diff --git a/doc/ref/misc-modules.texi b/doc/ref/misc-modules.texi
index 6cd0ad2ab..e17f9854b 100644
--- a/doc/ref/misc-modules.texi
+++ b/doc/ref/misc-modules.texi
@@ -159,9 +159,8 @@ instead of @nicode{%}, and are more powerful.
 @deffn {Scheme Procedure} format dest fmt [args@dots{}]
 Write output specified by the @var{fmt} string to @var{dest}.
 @var{dest} can be an output port, @code{#t} for
-@code{current-output-port} (@pxref{Default Ports}), a number for
-@code{current-error-port}, or @code{#f} to return the output as a
-string.
+@code{current-output-port} (@pxref{Default Ports}), or @code{#f} to
+return the output as a string.
 
 @var{fmt} can contain literal text to be output, and @nicode{~}
 escapes.  Each escape has the form
diff --git a/module/ice-9/format.scm b/module/ice-9/format.scm
index c802f29c3..6520a60ba 100644
--- a/module/ice-9/format.scm
+++ b/module/ice-9/format.scm
@@ -167,13 +167,17 @@
 	      (cond
 	       ((or (and (boolean? destination)	; port output
 			 destination)
-		    (output-port? destination)
-		    (number? destination))
+		    (output-port? destination))
 		(format:out (cond
 			     ((boolean? destination) (current-output-port))
 			     ((output-port? destination) destination)
 			     ((number? destination) (current-error-port)))
 			    (car arglist) (cdr arglist)))
+	       ((number? destination)
+                (issue-deprecation-warning
+                 "Passing a number to format as the destination is deprecated."
+                 "Pass (current-error-port) instead.")
+		(format:out (current-error-port) (car arglist) (cdr arglist)))
 	       ((and (boolean? destination)	; string output
 		     (not destination))
 		(call-with-output-string