CLOSE-CONSTRUCTED-STREAM
A "composite" stream is one created with MAKE-SYNONYM-STREAM, MAKE-BROADCAST-STREAM, MAKE-CONCATENATED-STREAM, MAKE-TWO-WAY-STREAM, MAKE-ECHO-STREAM.
The "constituents" of a composite stream are the streams it points to: the SYMBOL-VALUE of the symbol given to MAKE-SYNONYM-STREAM the streams given to MAKE-BROADCAST-STREAM or MAKE-CONCATENATED-STREAM the input-stream and output-stream given to MAKE-TWO-WAY-STREAM or MAKE-ECHO-STREAM.
A "constructed" stream is either a composite stream or one created with MAKE-STRING-INPUT-STREAM, MAKE-STRING-OUTPUT-STREAM, WITH-INPUT-FROM-STRING, WITH-OUTPUT-FROM-STRING.
The function "CLOSE" is currently described in 21.3, which starts "This section contains discussion of only those operations that are common to all streams." This would seem to imply that they apply to constructed streams.
The definition of CLOSE "The argument must be a stream. No further input/output operations may be performed on it. ... " It further states "... and it is permissible to close an already closed stream."
However, the behavior on the constructed streams is not well defined, and implementations (apparently) differ.
CLOSE on a constructed stream. CLOSE might signal an error, or the result of CLOSE could cause the constituent streams to be closed, etc, but the effect is implementation-dependent.CLOSE on a constructed stream signals an error.CLOSE on a constructed stream is to close the "argument" stream only. No i/o operations are permitted after the call to CLOSE on the stream given to CLOSE; There is no effect on the constituents of composite streams.
For streams created with MAKE-STRING-OUTPUT-STREAM, the result of GET-OUTPUT-STREAM-STRING is unspecified after CLOS. For composite streams, the call to CLOSE has no effect on any of the constituent streams.
The "links" to the constituents may be broken; if the proposal in STREAM-ACCESS passes, the results of the accessor functions there are unspecified after the call to CLOSE.)
CLOSE first closes its argument; it then operates recursively on the constituents of composite streams.CLOSE on composite streams.CLOSE on a composite stream. We could not come up with a legitimate case where you wouldn't instead close the underlying stream if that's what you wanted.
Allowing the result to be implementation dependent is the "status quo".
ARGUMENT-STREAM-ONLY is probably the "safest" in that it makes it harder to accidentally close a stream that wasn't intended. It seems counterintuitive and yet it probably wouldn't be harmful if it were well-defined that this was what it did.
CLOSE-CONSTITUENTS could be an incompatible change for some implementations. It makes more sense for things like broadcast streams (which are usually non-interactive) than it does for echo streams (which are sometimes interactive).