Proposed resolution:

Change [stringbuf.assign]/1:

basic_stringbuf& operator=(basic_stringbuf&& rhs);

-1- Effects: swap(rhs). After the move assignment *this reflects the same observable state it would have if it had been move constructed from rhs ([stringbuf.cons]).

Change [istringstream.assign]/1:

basic_istringstream& operator=(basic_istringstream&& rhs);

-1- Effects: swap(rhs). Move assigns the base and members of *this with the respective base and members of rhs.

Change [ostringstream.assign]/1:

basic_ostringstream& operator=(basic_ostringstream&& rhs);

-1- Effects: swap(rhs). Move assigns the base and members of *this with the respective base and members of rhs.

Change [stringstream.assign]/1:

basic_stringstream& operator=(basic_stringstream&& rhs);

-1- Effects: swap(rhs). Move assigns the base and members of *this with the respective base and members of rhs.

Change [filebuf.assign]/1:

basic_filebuf& operator=(basic_filebuf&& rhs);

-1- Effects: swap(rhs). Begins by calling this->close(). After the move assignment *this reflects the same observable state it would have if it had been move constructed from rhs ([filebuf.cons]).

Change [ifstream.assign]/1:

basic_ifstream& operator=(basic_ifstream&& rhs);

-1- Effects: swap(rhs). Move assigns the base and members of *this with the respective base and members of rhs.

Change [ofstream.assign]/1:

basic_ofstream& operator=(basic_ofstream&& rhs);

-1- Effects: swap(rhs). Move assigns the base and members of *this with the respective base and members of rhs.

Change [fstream.assign]/1:

basic_fstream& operator=(basic_fstream&& rhs);

-1- Effects: swap(rhs). Move assigns the base and members of *this with the respective base and members of rhs.

[ 2010 Pittsburgh: ]

Moved to Ready for Pittsburgh.

[ 2009 Santa Cruz: ]

Leave as Open. Too closely related to 911 to move on at this time.

[ 2009-09-13 Niels adds: ]

Note: The proposed change of [filebuf.assign] p1 depends on the resolution of LWG 1204, which allows implementations to assume that *this and rhs refer to different objects.

[ 2009-07-26 Howard provided wording. ]

[ 2009-07 Frankfurt: ]

Howard is going to write wording.

[ Batavia (2009-05): ]

Howard agrees with the analysis and the direction proposed.

Move to Open pending specific wording to be supplied by Howard.

It appears that we have an issue similar to issue 675 regarding the move-assignment of stream types. For example, when assigning to an std::ifstream, ifstream1, it seems preferable to close the file originally held by ifstream1:

ifstream1 = std::move(ifstream2); 

The current Draft (N2723) specifies that the move-assignment of stream types like ifstream has the same effect as a swap:

Assign and swap [ifstream.assign]

basic_ifstream& operator=(basic_ifstream&& rhs); 

Effects: swap(rhs).