src/pkg/[a-m]*: gofix -r error -force=error

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/5322051

43 files changed, 383 insertions, 392 deletions

diff --git a/src/pkg/exp/ebnf/ebnf.go b/src/pkg/exp/ebnf/ebnf.go
index 7070cc79fd..15c199af6c 100644
--- a/src/pkg/exp/ebnf/ebnf.go
+++ b/src/pkg/exp/ebnf/ebnf.go
@@ -23,8 +23,8 @@
 package ebnf
 
 import (
+	"errors"
 	"fmt"
-	"os"
 	"scanner"
 	"unicode"
 	"utf8"
@@ -33,27 +33,27 @@ import (
 // ----------------------------------------------------------------------------
 // Error handling
 
-type errorList []os.Error
+type errorList []error
 
-func (list errorList) Error() os.Error {
+func (list errorList) Err() error {
 	if len(list) == 0 {
 		return nil
 	}
 	return list
 }
 
-func (list errorList) String() string {
+func (list errorList) Error() string {
 	switch len(list) {
 	case 0:
 		return "no errors"
 	case 1:
-		return list[0].String()
+		return list[0].Error()
 	}
 	return fmt.Sprintf("%s (and %d more errors)", list[0], len(list)-1)
 }
 
-func newError(pos scanner.Position, msg string) os.Error {
-	return os.NewError(fmt.Sprintf("%s: %s", pos, msg))
+func newError(pos scanner.Position, msg string) error {
+	return errors.New(fmt.Sprintf("%s: %s", pos, msg))
 }
 
 // ----------------------------------------------------------------------------
@@ -262,8 +262,8 @@ func (v *verifier) verify(grammar Grammar, start string) {
 //
 // Position information is interpreted relative to the file set fset.
 //
-func Verify(grammar Grammar, start string) os.Error {
+func Verify(grammar Grammar, start string) error {
 	var v verifier
 	v.verify(grammar, start)
-	return v.errors.Error()
+	return v.errors.Err()
 }
diff --git a/src/pkg/exp/ebnf/parser.go b/src/pkg/exp/ebnf/parser.go
index b550c2b64f..2dad9b4c13 100644
--- a/src/pkg/exp/ebnf/parser.go
+++ b/src/pkg/exp/ebnf/parser.go
@@ -6,7 +6,6 @@ package ebnf
 
 import (
 	"io"
-	"os"
 	"scanner"
 	"strconv"
 )
@@ -184,7 +183,7 @@ func (p *parser) parse(filename string, src io.Reader) Grammar {
 // more than once; the filename is used only for error
 // positions.
 //
-func Parse(filename string, src io.Reader) (Grammar, os.Error) {
+func Parse(filename string, src io.Reader) (Grammar, error) {
 	var p parser
 	grammar := p.parse(filename, src)
 	return grammar, p.errors.Err()
diff --git a/src/pkg/exp/ebnflint/ebnflint.go b/src/pkg/exp/ebnflint/ebnflint.go
index c827716c44..6d6f516c90 100644
--- a/src/pkg/exp/ebnflint/ebnflint.go
+++ b/src/pkg/exp/ebnflint/ebnflint.go
@@ -31,7 +31,7 @@ var (
 	close = []byte(`</pre>`)
 )
 
-func report(err os.Error) {
+func report(err error) {
 	scanner.PrintError(os.Stderr, err)
 	os.Exit(1)
 }
@@ -78,7 +78,7 @@ func main() {
 	var (
 		filename string
 		src      []byte
-		err      os.Error
+		err      error
 	)
 	switch flag.NArg() {
 	case 0:
diff --git a/src/pkg/exp/gotype/gotype.go b/src/pkg/exp/gotype/gotype.go
index 9199213007..bc4a112c98 100644
--- a/src/pkg/exp/gotype/gotype.go
+++ b/src/pkg/exp/gotype/gotype.go
@@ -5,6 +5,7 @@
 package main
 
 import (
+	"errors"
 	"exp/types"
 	"flag"
 	"fmt"
@@ -38,7 +39,7 @@ func usage() {
 	os.Exit(2)
 }
 
-func report(err os.Error) {
+func report(err error) {
 	scanner.PrintError(os.Stderr, err)
 	exitCode = 2
 }
@@ -111,7 +112,7 @@ func parseFiles(fset *token.FileSet, filenames []string) (files map[string]*ast.
 		}
 		if file := parse(fset, filename, src); file != nil {
 			if files[filename] != nil {
-				report(os.NewError(fmt.Sprintf("%q: duplicate file", filename)))
+				report(errors.New(fmt.Sprintf("%q: duplicate file", filename)))
 				continue
 			}
 			files[filename] = file
diff --git a/src/pkg/exp/gui/gui.go b/src/pkg/exp/gui/gui.go
index 1714991860..a69f83a1f5 100644
--- a/src/pkg/exp/gui/gui.go
+++ b/src/pkg/exp/gui/gui.go
@@ -8,7 +8,6 @@ package gui
 import (
 	"image"
 	"image/draw"
-	"os"
 )
 
 // A Window represents a single graphics window.
@@ -21,7 +20,7 @@ type Window interface {
 	// mouse movements and window resizes.
 	EventChan() <-chan interface{}
 	// Close closes the window.
-	Close() os.Error
+	Close() error
 }
 
 // A KeyEvent is sent for a key press or release.
@@ -54,5 +53,5 @@ type ConfigEvent struct {
 
 // An ErrEvent is sent when an error occurs.
 type ErrEvent struct {
-	Err os.Error
+	Err error
 }
diff --git a/src/pkg/exp/gui/x11/auth.go b/src/pkg/exp/gui/x11/auth.go
index 732f103d66..24e941cb36 100644
--- a/src/pkg/exp/gui/x11/auth.go
+++ b/src/pkg/exp/gui/x11/auth.go
@@ -6,12 +6,13 @@ package x11
 
 import (
 	"bufio"
+	"errors"
 	"io"
 	"os"
 )
 
 // readU16BE reads a big-endian uint16 from r, using b as a scratch buffer.
-func readU16BE(r io.Reader, b []byte) (uint16, os.Error) {
+func readU16BE(r io.Reader, b []byte) (uint16, error) {
 	_, err := io.ReadFull(r, b[0:2])
 	if err != nil {
 		return 0, err
@@ -20,13 +21,13 @@ func readU16BE(r io.Reader, b []byte) (uint16, os.Error) {
 }
 
 // readStr reads a length-prefixed string from r, using b as a scratch buffer.
-func readStr(r io.Reader, b []byte) (string, os.Error) {
+func readStr(r io.Reader, b []byte) (string, error) {
 	n, err := readU16BE(r, b)
 	if err != nil {
 		return "", err
 	}
 	if int(n) > len(b) {
-		return "", os.NewError("Xauthority entry too long for buffer")
+		return "", errors.New("Xauthority entry too long for buffer")
 	}
 	_, err = io.ReadFull(r, b[0:n])
 	if err != nil {
@@ -37,7 +38,7 @@ func readStr(r io.Reader, b []byte) (string, os.Error) {
 
 // readAuth reads the X authority file and returns the name/data pair for the display.
 // displayStr is the "12" out of a $DISPLAY like ":12.0".
-func readAuth(displayStr string) (name, data string, err os.Error) {
+func readAuth(displayStr string) (name, data string, err error) {
 	// b is a scratch buffer to use and should be at least 256 bytes long
 	// (i.e. it should be able to hold a hostname).
 	var b [256]byte
@@ -48,7 +49,7 @@ func readAuth(displayStr string) (name, data string, err os.Error) {
 	if fn == "" {
 		home := os.Getenv("HOME")
 		if home == "" {
-			err = os.NewError("Xauthority not found: $XAUTHORITY, $HOME not set")
+			err = errors.New("Xauthority not found: $XAUTHORITY, $HOME not set")
 			return
 		}
 		fn = home + "/.Xauthority"
diff --git a/src/pkg/exp/gui/x11/conn.go b/src/pkg/exp/gui/x11/conn.go
index f4a453ede4..15afc657ec 100644
--- a/src/pkg/exp/gui/x11/conn.go
+++ b/src/pkg/exp/gui/x11/conn.go
@@ -10,6 +10,7 @@ package x11
 
 import (
 	"bufio"
+	"errors"
 	"exp/gui"
 	"image"
 	"image/draw"
@@ -86,7 +87,7 @@ func (c *conn) writeSocket() {
 		for y := b.Min.Y; y < b.Max.Y; y++ {
 			setU32LE(c.flushBuf0[16:20], uint32(y<<16))
 			if _, err := c.w.Write(c.flushBuf0[:24]); err != nil {
-				if err != os.EOF {
+				if err != io.EOF {
 					log.Println("x11:", err)
 				}
 				return
@@ -105,7 +106,7 @@ func (c *conn) writeSocket() {
 				}
 				x += nx
 				if _, err := c.w.Write(c.flushBuf1[:nx]); err != nil {
-					if err != os.EOF {
+					if err != io.EOF {
 						log.Println("x11:", err)
 					}
 					return
@@ -113,7 +114,7 @@ func (c *conn) writeSocket() {
 			}
 		}
 		if err := c.w.Flush(); err != nil {
-			if err != os.EOF {
+			if err != io.EOF {
 				log.Println("x11:", err)
 			}
 			return
@@ -133,7 +134,7 @@ func (c *conn) FlushImage() {
 	}
 }
 
-func (c *conn) Close() os.Error {
+func (c *conn) Close() error {
 	// Shut down the writeSocket goroutine. This will close the socket to the
 	// X11 server, which will cause c.eventc to close.
 	close(c.flush)
@@ -156,7 +157,7 @@ func (c *conn) readSocket() {
 	for {
 		// X events are always 32 bytes long.
 		if _, err := io.ReadFull(c.r, c.buf[:32]); err != nil {
-			if err != os.EOF {
+			if err != io.EOF {
 				c.eventc <- gui.ErrEvent{err}
 			}
 			return
@@ -167,7 +168,7 @@ func (c *conn) readSocket() {
 			if cookie != 1 {
 				// We issued only one request (GetKeyboardMapping) with a cookie of 1,
 				// so we shouldn't get any other reply from the X server.
-				c.eventc <- gui.ErrEvent{os.NewError("x11: unexpected cookie")}
+				c.eventc <- gui.ErrEvent{errors.New("x11: unexpected cookie")}
 				return
 			}
 			keysymsPerKeycode = int(c.buf[1])
@@ -180,7 +181,7 @@ func (c *conn) readSocket() {
 				for j := range m {
 					u, err := readU32LE(c.r, c.buf[:4])
 					if err != nil {
-						if err != os.EOF {
+						if err != io.EOF {
 							c.eventc <- gui.ErrEvent{err}
 						}
 						return
@@ -253,10 +254,10 @@ func (c *conn) readSocket() {
 //	connect("/tmp/launch-123/:0") // calls net.Dial("unix", "", "/tmp/launch-123/:0"), displayStr="0"
 //	connect("hostname:2.1")       // calls net.Dial("tcp", "", "hostname:6002"), displayStr="2"
 //	connect("tcp/hostname:1.0")   // calls net.Dial("tcp", "", "hostname:6001"), displayStr="1"
-func connect(display string) (conn net.Conn, displayStr string, err os.Error) {
+func connect(display string) (conn net.Conn, displayStr string, err error) {
 	colonIdx := strings.LastIndex(display, ":")
 	if colonIdx < 0 {
-		return nil, "", os.NewError("bad display: " + display)
+		return nil, "", errors.New("bad display: " + display)
 	}
 	// Parse the section before the colon.
 	var protocol, host, socket string
@@ -275,7 +276,7 @@ func connect(display string) (conn net.Conn, displayStr string, err os.Error) {
 	// Parse the section after the colon.
 	after := display[colonIdx+1:]
 	if after == "" {
-		return nil, "", os.NewError("bad display: " + display)
+		return nil, "", errors.New("bad display: " + display)
 	}
 	if i := strings.LastIndex(after, "."); i < 0 {
 		displayStr = after
@@ -284,7 +285,7 @@ func connect(display string) (conn net.Conn, displayStr string, err os.Error) {
 	}
 	displayInt, err := strconv.Atoi(displayStr)
 	if err != nil || displayInt < 0 {
-		return nil, "", os.NewError("bad display: " + display)
+		return nil, "", errors.New("bad display: " + display)
 	}
 	// Make the connection.
 	if socket != "" {
@@ -295,21 +296,21 @@ func connect(display string) (conn net.Conn, displayStr string, err os.Error) {
 		conn, err = net.Dial("unix", "/tmp/.X11-unix/X"+displayStr)
 	}
 	if err != nil {
-		return nil, "", os.NewError("cannot connect to " + display + ": " + err.String())
+		return nil, "", errors.New("cannot connect to " + display + ": " + err.Error())
 	}
 	return
 }
 
 // authenticate authenticates ourselves with the X server.
 // displayStr is the "12" out of ":12.0".
-func authenticate(w *bufio.Writer, displayStr string) os.Error {
+func authenticate(w *bufio.Writer, displayStr string) error {
 	key, value, err := readAuth(displayStr)
 	if err != nil {
 		return err
 	}
 	// Assume that the authentication protocol is "MIT-MAGIC-COOKIE-1".
 	if len(key) != 18 || len(value) != 16 {
-		return os.NewError("unsupported Xauth")
+		return errors.New("unsupported Xauth")
 	}
 	// 0x006c means little-endian. 0x000b, 0x0000 means X major version 11, minor version 0.
 	// 0x0012 and 0x0010 means the auth key and value have lengths 18 and 16.
@@ -339,7 +340,7 @@ func authenticate(w *bufio.Writer, displayStr string) os.Error {
 }
 
 // readU8 reads a uint8 from r, using b as a scratch buffer.
-func readU8(r io.Reader, b []byte) (uint8, os.Error) {
+func readU8(r io.Reader, b []byte) (uint8, error) {
 	_, err := io.ReadFull(r, b[:1])
 	if err != nil {
 		return 0, err
@@ -348,7 +349,7 @@ func readU8(r io.Reader, b []byte) (uint8, os.Error) {
 }
 
 // readU16LE reads a little-endian uint16 from r, using b as a scratch buffer.
-func readU16LE(r io.Reader, b []byte) (uint16, os.Error) {
+func readU16LE(r io.Reader, b []byte) (uint16, error) {
 	_, err := io.ReadFull(r, b[:2])
 	if err != nil {
 		return 0, err
@@ -357,7 +358,7 @@ func readU16LE(r io.Reader, b []byte) (uint16, os.Error) {
 }
 
 // readU32LE reads a little-endian uint32 from r, using b as a scratch buffer.
-func readU32LE(r io.Reader, b []byte) (uint32, os.Error) {
+func readU32LE(r io.Reader, b []byte) (uint32, error) {
 	_, err := io.ReadFull(r, b[:4])
 	if err != nil {
 		return 0, err
@@ -374,7 +375,7 @@ func setU32LE(b []byte, u uint32) {
 }
 
 // checkPixmapFormats checks that we have an agreeable X pixmap Format.
-func checkPixmapFormats(r io.Reader, b []byte, n int) (agree bool, err os.Error) {
+func checkPixmapFormats(r io.Reader, b []byte, n int) (agree bool, err error) {
 	for i := 0; i < n; i++ {
 		_, err = io.ReadFull(r, b[:8])
 		if err != nil {
@@ -389,7 +390,7 @@ func checkPixmapFormats(r io.Reader, b []byte, n int) (agree bool, err os.Error)
 }
 
 // checkDepths checks that we have an agreeable X Depth (i.e. one that has an agreeable X VisualType).
-func checkDepths(r io.Reader, b []byte, n int, visual uint32) (agree bool, err os.Error) {
+func checkDepths(r io.Reader, b []byte, n int, visual uint32) (agree bool, err error) {
 	for i := 0; i < n; i++ {
 		var depth, visualsLen uint16
 		depth, err = readU16LE(r, b)
@@ -427,7 +428,7 @@ func checkDepths(r io.Reader, b []byte, n int, visual uint32) (agree bool, err o
 }
 
 // checkScreens checks that we have an agreeable X Screen.
-func checkScreens(r io.Reader, b []byte, n int) (root, visual uint32, err os.Error) {
+func checkScreens(r io.Reader, b []byte, n int) (root, visual uint32, err error) {
 	for i := 0; i < n; i++ {
 		var root0, visual0, x uint32
 		root0, err = readU32LE(r, b)
@@ -465,14 +466,14 @@ func checkScreens(r io.Reader, b []byte, n int) (root, visual uint32, err os.Err
 
 // handshake performs the protocol handshake with the X server, and ensures
 // that the server provides a compatible Screen, Depth, etc.
-func (c *conn) handshake() os.Error {
+func (c *conn) handshake() error {
 	_, err := io.ReadFull(c.r, c.buf[:8])
 	if err != nil {
 		return err
 	}
 	// Byte 0 should be 1 (success), bytes 2:6 should be 0xb0000000 (major/minor version 11.0).
 	if c.buf[0] != 1 || c.buf[2] != 11 || c.buf[3] != 0 || c.buf[4] != 0 || c.buf[5] != 0 {
-		return os.NewError("unsupported X version")
+		return errors.New("unsupported X version")
 	}
 	// Ignore the release number.
 	_, err = io.ReadFull(c.r, c.buf[:4])
@@ -490,7 +491,7 @@ func (c *conn) handshake() os.Error {
 		return err
 	}
 	if resourceIdMask < 256 {
-		return os.NewError("X resource ID mask is too small")
+		return errors.New("X resource ID mask is too small")
 	}
 	// Ignore the motion buffer size.
 	_, err = io.ReadFull(c.r, c.buf[:4])
@@ -510,7 +511,7 @@ func (c *conn) handshake() os.Error {
 		return err
 	}
 	if maxReqLen != 0xffff {
-		return os.NewError("unsupported X maximum request length")
+		return errors.New("unsupported X maximum request length")
 	}
 	// Read the roots length.
 	rootsLen, err := readU8(c.r, c.buf[:1])
@@ -526,7 +527,7 @@ func (c *conn) handshake() os.Error {
 	// imageByteOrder(1), bitmapFormatBitOrder(1), bitmapFormatScanlineUnit(1) bitmapFormatScanlinePad(1),
 	// minKeycode(1), maxKeycode(1), padding(4), vendor (vendorLen).
 	if 10+int(vendorLen) > cap(c.buf) {
-		return os.NewError("unsupported X vendor")
+		return errors.New("unsupported X vendor")
 	}
 	_, err = io.ReadFull(c.r, c.buf[:10+int(vendorLen)])
 	if err != nil {
@@ -538,7 +539,7 @@ func (c *conn) handshake() os.Error {
 		return err
 	}
 	if !agree {
-		return os.NewError("unsupported X pixmap formats")
+		return errors.New("unsupported X pixmap formats")
 	}
 	// Check that we have an agreeable screen.
 	root, visual, err := checkScreens(c.r, c.buf[:24], int(rootsLen))
@@ -546,7 +547,7 @@ func (c *conn) handshake() os.Error {
 		return err
 	}
 	if root == 0 || visual == 0 {
-		return os.NewError("unsupported X screen")
+		return errors.New("unsupported X screen")
 	}
 	c.gc = resID(resourceIdBase)
 	c.window = resID(resourceIdBase + 1)
@@ -556,10 +557,10 @@ func (c *conn) handshake() os.Error {
 }
 
 // NewWindow calls NewWindowDisplay with $DISPLAY.
-func NewWindow() (gui.Window, os.Error) {
+func NewWindow() (gui.Window, error) {
 	display := os.Getenv("DISPLAY")
 	if len(display) == 0 {
-		return nil, os.NewError("$DISPLAY not set")
+		return nil, errors.New("$DISPLAY not set")
 	}
 	return NewWindowDisplay(display)
 }
@@ -567,7 +568,7 @@ func NewWindow() (gui.Window, os.Error) {
 // NewWindowDisplay returns a new gui.Window, backed by a newly created and
 // mapped X11 window. The X server to connect to is specified by the display
 // string, such as ":1".
-func NewWindowDisplay(display string) (gui.Window, os.Error) {
+func NewWindowDisplay(display string) (gui.Window, error) {
 	socket, displayStr, err := connect(display)
 	if err != nil {
 		return nil, err
diff --git a/src/pkg/exp/inotify/inotify_linux.go b/src/pkg/exp/inotify/inotify_linux.go
index ee3c75f63b..d6b7e8514e 100644
--- a/src/pkg/exp/inotify/inotify_linux.go
+++ b/src/pkg/exp/inotify/inotify_linux.go
@@ -27,6 +27,7 @@ Example:
 package inotify
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -49,14 +50,14 @@ type Watcher struct {
 	fd       int               // File descriptor (as returned by the inotify_init() syscall)
 	watches  map[string]*watch // Map of inotify watches (key: path)
 	paths    map[int]string    // Map of watched paths (key: watch descriptor)
-	Error    chan os.Error     // Errors are sent on this channel
+	Error    chan error        // Errors are sent on this channel
 	Event    chan *Event       // Events are returned on this channel
 	done     chan bool         // Channel for sending a "quit message" to the reader goroutine
 	isClosed bool              // Set to true when Close() is first called
 }
 
 // NewWatcher creates and returns a new inotify instance using inotify_init(2)
-func NewWatcher() (*Watcher, os.Error) {
+func NewWatcher() (*Watcher, error) {
 	fd, errno := syscall.InotifyInit()
 	if fd == -1 {
 		return nil, os.NewSyscallError("inotify_init", errno)
@@ -66,7 +67,7 @@ func NewWatcher() (*Watcher, os.Error) {
 		watches: make(map[string]*watch),
 		paths:   make(map[int]string),
 		Event:   make(chan *Event),
-		Error:   make(chan os.Error),
+		Error:   make(chan error),
 		done:    make(chan bool, 1),
 	}
 
@@ -77,7 +78,7 @@ func NewWatcher() (*Watcher, os.Error) {
 // Close closes an inotify watcher instance
 // It sends a message to the reader goroutine to quit and removes all watches
 // associated with the inotify instance
-func (w *Watcher) Close() os.Error {
+func (w *Watcher) Close() error {
 	if w.isClosed {
 		return nil
 	}
@@ -94,9 +95,9 @@ func (w *Watcher) Close() os.Error {
 
 // AddWatch adds path to the watched file set.
 // The flags are interpreted as described in inotify_add_watch(2).
-func (w *Watcher) AddWatch(path string, flags uint32) os.Error {
+func (w *Watcher) AddWatch(path string, flags uint32) error {
 	if w.isClosed {
-		return os.NewError("inotify instance already closed")
+		return errors.New("inotify instance already closed")
 	}
 
 	watchEntry, found := w.watches[path]
@@ -117,15 +118,15 @@ func (w *Watcher) AddWatch(path string, flags uint32) os.Error {
 }
 
 // Watch adds path to the watched file set, watching all events.
-func (w *Watcher) Watch(path string) os.Error {
+func (w *Watcher) Watch(path string) error {
 	return w.AddWatch(path, IN_ALL_EVENTS)
 }
 
 // RemoveWatch removes path from the watched file set.
-func (w *Watcher) RemoveWatch(path string) os.Error {
+func (w *Watcher) RemoveWatch(path string) error {
 	watch, ok := w.watches[path]
 	if !ok {
-		return os.NewError(fmt.Sprintf("can't remove non-existent inotify watch for: %s", path))
+		return errors.New(fmt.Sprintf("can't remove non-existent inotify watch for: %s", path))
 	}
 	success, errno := syscall.InotifyRmWatch(w.fd, watch.wd)
 	if success == -1 {
@@ -168,7 +169,7 @@ func (w *Watcher) readEvents() {
 			continue
 		}
 		if n < syscall.SizeofInotifyEvent {
-			w.Error <- os.NewError("inotify: short read in readEvents()")
+			w.Error <- errors.New("inotify: short read in readEvents()")
 			continue
 		}
 
diff --git a/src/pkg/exp/norm/maketables.go b/src/pkg/exp/norm/maketables.go
index 93edf221ef..c7a3762bde 100644
--- a/src/pkg/exp/norm/maketables.go
+++ b/src/pkg/exp/norm/maketables.go
@@ -220,7 +220,7 @@ func openReader(file string) (input io.ReadCloser) {
 	return
 }
 
-func parseDecomposition(s string, skipfirst bool) (a []rune, e os.Error) {
+func parseDecomposition(s string, skipfirst bool) (a []rune, e error) {
 	decomp := strings.Split(s, " ")
 	if len(decomp) > 0 && skipfirst {
 		decomp = decomp[1:]
@@ -310,7 +310,7 @@ func loadUnicodeData() {
 	for {
 		line, err := input.ReadString('\n')
 		if err != nil {
-			if err == os.EOF {
+			if err == io.EOF {
 				break
 			}
 			logger.Fatal(err)
@@ -350,7 +350,7 @@ func loadCompositionExclusions() {
 	for {
 		line, err := input.ReadString('\n')
 		if err != nil {
-			if err == os.EOF {
+			if err == io.EOF {
 				break
 			}
 			logger.Fatal(err)
@@ -782,7 +782,7 @@ func testDerived() {
 	for {
 		line, err := input.ReadString('\n')
 		if err != nil {
-			if err == os.EOF {
+			if err == io.EOF {
 				break
 			}
 			logger.Fatal(err)
diff --git a/src/pkg/exp/norm/normregtest.go b/src/pkg/exp/norm/normregtest.go
index cf3b34023b..6e27f638aa 100644
--- a/src/pkg/exp/norm/normregtest.go
+++ b/src/pkg/exp/norm/normregtest.go
@@ -11,6 +11,7 @@ import (
 	"flag"
 	"fmt"
 	"http"
+	"io"
 	"log"
 	"os"
 	"path"
@@ -141,7 +142,7 @@ func loadTestData() {
 	for {
 		line, err := input.ReadString('\n')
 		if err != nil {
-			if err == os.EOF {
+			if err == io.EOF {
 				break
 			}
 			logger.Fatal(err)
diff --git a/src/pkg/exp/norm/readwriter.go b/src/pkg/exp/norm/readwriter.go
index 48ae135620..ee58abd22d 100644
--- a/src/pkg/exp/norm/readwriter.go
+++ b/src/pkg/exp/norm/readwriter.go
@@ -4,10 +4,7 @@
 
 package norm
 
-import (
-	"io"
-	"os"
-)
+import "io"
 
 type normWriter struct {
 	rb  reorderBuffer
@@ -18,7 +15,7 @@ type normWriter struct {
 // Write implements the standard write interface.  If the last characters are
 // not at a normalization boundary, the bytes will be buffered for the next
 // write. The remaining bytes will be written on close.
-func (w *normWriter) Write(data []byte) (n int, err os.Error) {
+func (w *normWriter) Write(data []byte) (n int, err error) {
 	// Process data in pieces to keep w.buf size bounded.
 	const chunk = 4000
 
@@ -52,7 +49,7 @@ func (w *normWriter) Write(data []byte) (n int, err os.Error) {
 }
 
 // Close forces data that remains in the buffer to be written.
-func (w *normWriter) Close() os.Error {
+func (w *normWriter) Close() error {
 	if len(w.buf) > 0 {
 		_, err := w.w.Write(w.buf)
 		if err != nil {
@@ -79,11 +76,11 @@ type normReader struct {
 	outbuf       []byte
 	bufStart     int
 	lastBoundary int
-	err          os.Error
+	err          error
 }
 
 // Read implements the standard read interface.
-func (r *normReader) Read(p []byte) (int, os.Error) {
+func (r *normReader) Read(p []byte) (int, error) {
 	for {
 		if r.lastBoundary-r.bufStart > 0 {
 			n := copy(p, r.outbuf[r.bufStart:r.lastBoundary])
@@ -106,7 +103,7 @@ func (r *normReader) Read(p []byte) (int, os.Error) {
 		if n > 0 {
 			r.outbuf = doAppend(&r.rb, r.outbuf)
 		}
-		if err == os.EOF {
+		if err == io.EOF {
 			r.lastBoundary = len(r.outbuf)
 		} else {
 			r.lastBoundary = lastBoundary(&r.rb.f, r.outbuf)
diff --git a/src/pkg/exp/norm/readwriter_test.go b/src/pkg/exp/norm/readwriter_test.go
index 68652efa65..3b49eb0a2f 100644
--- a/src/pkg/exp/norm/readwriter_test.go
+++ b/src/pkg/exp/norm/readwriter_test.go
@@ -7,7 +7,6 @@ package norm
 import (
 	"bytes"
 	"fmt"
-	"os"
 	"strings"
 	"testing"
 )
@@ -27,7 +26,7 @@ func readFunc(size int) appendFunc {
 		r := f.Reader(bytes.NewBuffer(out))
 		buf := make([]byte, size)
 		result := []byte{}
-		for n, err := 0, os.Error(nil); err == nil; {
+		for n, err := 0, error(nil); err == nil; {
 			n, err = r.Read(buf)
 			result = append(result, buf[:n]...)
 		}
diff --git a/src/pkg/exp/spdy/read.go b/src/pkg/exp/spdy/read.go
index 2b1fd3d0d4..3de80c04d7 100644
--- a/src/pkg/exp/spdy/read.go
+++ b/src/pkg/exp/spdy/read.go
@@ -9,19 +9,18 @@ import (
 	"encoding/binary"
 	"http"
 	"io"
-	"os"
 	"strings"
 )
 
-func (frame *SynStreamFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *SynStreamFrame) read(h ControlFrameHeader, f *Framer) error {
 	return f.readSynStreamFrame(h, frame)
 }
 
-func (frame *SynReplyFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *SynReplyFrame) read(h ControlFrameHeader, f *Framer) error {
 	return f.readSynReplyFrame(h, frame)
 }
 
-func (frame *RstStreamFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *RstStreamFrame) read(h ControlFrameHeader, f *Framer) error {
 	frame.CFHeader = h
 	if err := binary.Read(f.r, binary.BigEndian, &frame.StreamId); err != nil {
 		return err
@@ -32,7 +31,7 @@ func (frame *RstStreamFrame) read(h ControlFrameHeader, f *Framer) os.Error {
 	return nil
 }
 
-func (frame *SettingsFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *SettingsFrame) read(h ControlFrameHeader, f *Framer) error {
 	frame.CFHeader = h
 	var numSettings uint32
 	if err := binary.Read(f.r, binary.BigEndian, &numSettings); err != nil {
@@ -52,12 +51,12 @@ func (frame *SettingsFrame) read(h ControlFrameHeader, f *Framer) os.Error {
 	return nil
 }
 
-func (frame *NoopFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *NoopFrame) read(h ControlFrameHeader, f *Framer) error {
 	frame.CFHeader = h
 	return nil
 }
 
-func (frame *PingFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *PingFrame) read(h ControlFrameHeader, f *Framer) error {
 	frame.CFHeader = h
 	if err := binary.Read(f.r, binary.BigEndian, &frame.Id); err != nil {
 		return err
@@ -65,7 +64,7 @@ func (frame *PingFrame) read(h ControlFrameHeader, f *Framer) os.Error {
 	return nil
 }
 
-func (frame *GoAwayFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *GoAwayFrame) read(h ControlFrameHeader, f *Framer) error {
 	frame.CFHeader = h
 	if err := binary.Read(f.r, binary.BigEndian, &frame.LastGoodStreamId); err != nil {
 		return err
@@ -73,11 +72,11 @@ func (frame *GoAwayFrame) read(h ControlFrameHeader, f *Framer) os.Error {
 	return nil
 }
 
-func (frame *HeadersFrame) read(h ControlFrameHeader, f *Framer) os.Error {
+func (frame *HeadersFrame) read(h ControlFrameHeader, f *Framer) error {
 	return f.readHeadersFrame(h, frame)
 }
 
-func newControlFrame(frameType ControlFrameType) (controlFrame, os.Error) {
+func newControlFrame(frameType ControlFrameType) (controlFrame, error) {
 	ctor, ok := cframeCtor[frameType]
 	if !ok {
 		return nil, &Error{Err: InvalidControlFrame}
@@ -97,7 +96,7 @@ var cframeCtor = map[ControlFrameType]func() controlFrame{
 	// TODO(willchan): Add TypeWindowUpdate
 }
 
-func (f *Framer) uncorkHeaderDecompressor(payloadSize int64) os.Error {
+func (f *Framer) uncorkHeaderDecompressor(payloadSize int64) error {
 	if f.headerDecompressor != nil {
 		f.headerReader.N = payloadSize
 		return nil
@@ -112,7 +111,7 @@ func (f *Framer) uncorkHeaderDecompressor(payloadSize int64) os.Error {
 }
 
 // ReadFrame reads SPDY encoded data and returns a decompressed Frame.
-func (f *Framer) ReadFrame() (Frame, os.Error) {
+func (f *Framer) ReadFrame() (Frame, error) {
 	var firstWord uint32
 	if err := binary.Read(f.r, binary.BigEndian, &firstWord); err != nil {
 		return nil, err
@@ -125,7 +124,7 @@ func (f *Framer) ReadFrame() (Frame, os.Error) {
 	return f.parseDataFrame(firstWord & 0x7fffffff)
 }
 
-func (f *Framer) parseControlFrame(version uint16, frameType ControlFrameType) (Frame, os.Error) {
+func (f *Framer) parseControlFrame(version uint16, frameType ControlFrameType) (Frame, error) {
 	var length uint32
 	if err := binary.Read(f.r, binary.BigEndian, &length); err != nil {
 		return nil, err
@@ -143,12 +142,12 @@ func (f *Framer) parseControlFrame(version uint16, frameType ControlFrameType) (
 	return cframe, nil
 }
 
-func parseHeaderValueBlock(r io.Reader, streamId uint32) (http.Header, os.Error) {
+func parseHeaderValueBlock(r io.Reader, streamId uint32) (http.Header, error) {
 	var numHeaders uint16
 	if err := binary.Read(r, binary.BigEndian, &numHeaders); err != nil {
 		return nil, err
 	}
-	var e os.Error
+	var e error
 	h := make(http.Header, int(numHeaders))
 	for i := 0; i < int(numHeaders); i++ {
 		var length uint16
@@ -185,9 +184,9 @@ func parseHeaderValueBlock(r io.Reader, streamId uint32) (http.Header, os.Error)
 	return h, nil
 }
 
-func (f *Framer) readSynStreamFrame(h ControlFrameHeader, frame *SynStreamFrame) os.Error {
+func (f *Framer) readSynStreamFrame(h ControlFrameHeader, frame *SynStreamFrame) error {
 	frame.CFHeader = h
-	var err os.Error
+	var err error
 	if err = binary.Read(f.r, binary.BigEndian, &frame.StreamId); err != nil {
 		return err
 	}
@@ -206,7 +205,7 @@ func (f *Framer) readSynStreamFrame(h ControlFrameHeader, frame *SynStreamFrame)
 	}
 
 	frame.Headers, err = parseHeaderValueBlock(reader, frame.StreamId)
-	if !f.headerCompressionDisabled && ((err == os.EOF && f.headerReader.N == 0) || f.headerReader.N != 0) {
+	if !f.headerCompressionDisabled && ((err == io.EOF && f.headerReader.N == 0) || f.headerReader.N != 0) {
 		err = &Error{WrongCompressedPayloadSize, 0}
 	}
 	if err != nil {
@@ -223,9 +222,9 @@ func (f *Framer) readSynStreamFrame(h ControlFrameHeader, frame *SynStreamFrame)
 	return nil
 }
 
-func (f *Framer) readSynReplyFrame(h ControlFrameHeader, frame *SynReplyFrame) os.Error {
+func (f *Framer) readSynReplyFrame(h ControlFrameHeader, frame *SynReplyFrame) error {
 	frame.CFHeader = h
-	var err os.Error
+	var err error
 	if err = binary.Read(f.r, binary.BigEndian, &frame.StreamId); err != nil {
 		return err
 	}
@@ -239,7 +238,7 @@ func (f *Framer) readSynReplyFrame(h ControlFrameHeader, frame *SynReplyFrame) o
 		reader = f.headerDecompressor
 	}
 	frame.Headers, err = parseHeaderValueBlock(reader, frame.StreamId)
-	if !f.headerCompressionDisabled && ((err == os.EOF && f.headerReader.N == 0) || f.headerReader.N != 0) {
+	if !f.headerCompressionDisabled && ((err == io.EOF && f.headerReader.N == 0) || f.headerReader.N != 0) {
 		err = &Error{WrongCompressedPayloadSize, 0}
 	}
 	if err != nil {
@@ -256,9 +255,9 @@ func (f *Framer) readSynReplyFrame(h ControlFrameHeader, frame *SynReplyFrame) o
 	return nil
 }
 
-func (f *Framer) readHeadersFrame(h ControlFrameHeader, frame *HeadersFrame) os.Error {
+func (f *Framer) readHeadersFrame(h ControlFrameHeader, frame *HeadersFrame) error {
 	frame.CFHeader = h
-	var err os.Error
+	var err error
 	if err = binary.Read(f.r, binary.BigEndian, &frame.StreamId); err != nil {
 		return err
 	}
@@ -272,7 +271,7 @@ func (f *Framer) readHeadersFrame(h ControlFrameHeader, frame *HeadersFrame) os.
 		reader = f.headerDecompressor
 	}
 	frame.Headers, err = parseHeaderValueBlock(reader, frame.StreamId)
-	if !f.headerCompressionDisabled && ((err == os.EOF && f.headerReader.N == 0) || f.headerReader.N != 0) {
+	if !f.headerCompressionDisabled && ((err == io.EOF && f.headerReader.N == 0) || f.headerReader.N != 0) {
 		err = &Error{WrongCompressedPayloadSize, 0}
 	}
 	if err != nil {
@@ -296,7 +295,7 @@ func (f *Framer) readHeadersFrame(h ControlFrameHeader, frame *HeadersFrame) os.
 	return nil
 }
 
-func (f *Framer) parseDataFrame(streamId uint32) (*DataFrame, os.Error) {
+func (f *Framer) parseDataFrame(streamId uint32) (*DataFrame, error) {
 	var length uint32
 	if err := binary.Read(f.r, binary.BigEndian, &length); err != nil {
 		return nil, err
diff --git a/src/pkg/exp/spdy/types.go b/src/pkg/exp/spdy/types.go
index 41cafb1741..87d6edbd56 100644
--- a/src/pkg/exp/spdy/types.go
+++ b/src/pkg/exp/spdy/types.go
@@ -9,7 +9,6 @@ import (
 	"compress/zlib"
 	"http"
 	"io"
-	"os"
 )
 
 //  Data Frame Format
@@ -161,7 +160,7 @@ const MaxDataLength = 1<<24 - 1
 // Frame is a single SPDY frame in its unpacked in-memory representation. Use
 // Framer to read and write it.
 type Frame interface {
-	write(f *Framer) os.Error
+	write(f *Framer) error
 }
 
 // ControlFrameHeader contains all the fields in a control frame header,
@@ -176,7 +175,7 @@ type ControlFrameHeader struct {
 
 type controlFrame interface {
 	Frame
-	read(h ControlFrameHeader, f *Framer) os.Error
+	read(h ControlFrameHeader, f *Framer) error
 }
 
 // SynStreamFrame is the unpacked, in-memory representation of a SYN_STREAM
@@ -321,7 +320,7 @@ type Error struct {
 	StreamId uint32
 }
 
-func (e *Error) String() string {
+func (e *Error) Error() string {
 	return string(e.Err)
 }
 
@@ -354,7 +353,7 @@ type Framer struct {
 // a io.Writer and io.Reader. Note that Framer will read and write individual fields 
 // from/to the Reader and Writer, so the caller should pass in an appropriately 
 // buffered implementation to optimize performance.
-func NewFramer(w io.Writer, r io.Reader) (*Framer, os.Error) {
+func NewFramer(w io.Writer, r io.Reader) (*Framer, error) {
 	compressBuf := new(bytes.Buffer)
 	compressor, err := zlib.NewWriterDict(compressBuf, zlib.BestCompression, []byte(HeaderDictionary))
 	if err != nil {
diff --git a/src/pkg/exp/spdy/write.go b/src/pkg/exp/spdy/write.go
index 7d40bbe9fe..537154fbd3 100644
--- a/src/pkg/exp/spdy/write.go
+++ b/src/pkg/exp/spdy/write.go
@@ -8,19 +8,18 @@ import (
 	"encoding/binary"
 	"http"
 	"io"
-	"os"
 	"strings"
 )
 
-func (frame *SynStreamFrame) write(f *Framer) os.Error {
+func (frame *SynStreamFrame) write(f *Framer) error {
 	return f.writeSynStreamFrame(frame)
 }
 
-func (frame *SynReplyFrame) write(f *Framer) os.Error {
+func (frame *SynReplyFrame) write(f *Framer) error {
 	return f.writeSynReplyFrame(frame)
 }
 
-func (frame *RstStreamFrame) write(f *Framer) (err os.Error) {
+func (frame *RstStreamFrame) write(f *Framer) (err error) {
 	frame.CFHeader.version = Version
 	frame.CFHeader.frameType = TypeRstStream
 	frame.CFHeader.length = 8
@@ -38,7 +37,7 @@ func (frame *RstStreamFrame) write(f *Framer) (err os.Error) {
 	return
 }
 
-func (frame *SettingsFrame) write(f *Framer) (err os.Error) {
+func (frame *SettingsFrame) write(f *Framer) (err error) {
 	frame.CFHeader.version = Version
 	frame.CFHeader.frameType = TypeSettings
 	frame.CFHeader.length = uint32(len(frame.FlagIdValues)*8 + 4)
@@ -62,7 +61,7 @@ func (frame *SettingsFrame) write(f *Framer) (err os.Error) {
 	return
 }
 
-func (frame *NoopFrame) write(f *Framer) os.Error {
+func (frame *NoopFrame) write(f *Framer) error {
 	frame.CFHeader.version = Version
 	frame.CFHeader.frameType = TypeNoop
 
@@ -70,7 +69,7 @@ func (frame *NoopFrame) write(f *Framer) os.Error {
 	return writeControlFrameHeader(f.w, frame.CFHeader)
 }
 
-func (frame *PingFrame) write(f *Framer) (err os.Error) {
+func (frame *PingFrame) write(f *Framer) (err error) {
 	frame.CFHeader.version = Version
 	frame.CFHeader.frameType = TypePing
 	frame.CFHeader.length = 4
@@ -85,7 +84,7 @@ func (frame *PingFrame) write(f *Framer) (err os.Error) {
 	return
 }
 
-func (frame *GoAwayFrame) write(f *Framer) (err os.Error) {
+func (frame *GoAwayFrame) write(f *Framer) (err error) {
 	frame.CFHeader.version = Version
 	frame.CFHeader.frameType = TypeGoAway
 	frame.CFHeader.length = 4
@@ -100,20 +99,20 @@ func (frame *GoAwayFrame) write(f *Framer) (err os.Error) {
 	return nil
 }
 
-func (frame *HeadersFrame) write(f *Framer) os.Error {
+func (frame *HeadersFrame) write(f *Framer) error {
 	return f.writeHeadersFrame(frame)
 }
 
-func (frame *DataFrame) write(f *Framer) os.Error {
+func (frame *DataFrame) write(f *Framer) error {
 	return f.writeDataFrame(frame)
 }
 
 // WriteFrame writes a frame.
-func (f *Framer) WriteFrame(frame Frame) os.Error {
+func (f *Framer) WriteFrame(frame Frame) error {
 	return frame.write(f)
 }
 
-func writeControlFrameHeader(w io.Writer, h ControlFrameHeader) os.Error {
+func writeControlFrameHeader(w io.Writer, h ControlFrameHeader) error {
 	if err := binary.Write(w, binary.BigEndian, 0x8000|h.version); err != nil {
 		return err
 	}
@@ -127,7 +126,7 @@ func writeControlFrameHeader(w io.Writer, h ControlFrameHeader) os.Error {
 	return nil
 }
 
-func writeHeaderValueBlock(w io.Writer, h http.Header) (n int, err os.Error) {
+func writeHeaderValueBlock(w io.Writer, h http.Header) (n int, err error) {
 	n = 0
 	if err = binary.Write(w, binary.BigEndian, uint16(len(h))); err != nil {
 		return
@@ -156,7 +155,7 @@ func writeHeaderValueBlock(w io.Writer, h http.Header) (n int, err os.Error) {
 	return
 }
 
-func (f *Framer) writeSynStreamFrame(frame *SynStreamFrame) (err os.Error) {
+func (f *Framer) writeSynStreamFrame(frame *SynStreamFrame) (err error) {
 	// Marshal the headers.
 	var writer io.Writer = f.headerBuf
 	if !f.headerCompressionDisabled {
@@ -194,7 +193,7 @@ func (f *Framer) writeSynStreamFrame(frame *SynStreamFrame) (err os.Error) {
 	return nil
 }
 
-func (f *Framer) writeSynReplyFrame(frame *SynReplyFrame) (err os.Error) {
+func (f *Framer) writeSynReplyFrame(frame *SynReplyFrame) (err error) {
 	// Marshal the headers.
 	var writer io.Writer = f.headerBuf
 	if !f.headerCompressionDisabled {
@@ -229,7 +228,7 @@ func (f *Framer) writeSynReplyFrame(frame *SynReplyFrame) (err os.Error) {
 	return
 }
 
-func (f *Framer) writeHeadersFrame(frame *HeadersFrame) (err os.Error) {
+func (f *Framer) writeHeadersFrame(frame *HeadersFrame) (err error) {
 	// Marshal the headers.
 	var writer io.Writer = f.headerBuf
 	if !f.headerCompressionDisabled {
@@ -264,7 +263,7 @@ func (f *Framer) writeHeadersFrame(frame *HeadersFrame) (err os.Error) {
 	return
 }
 
-func (f *Framer) writeDataFrame(frame *DataFrame) (err os.Error) {
+func (f *Framer) writeDataFrame(frame *DataFrame) (err error) {
 	// Validate DataFrame
 	if frame.StreamId&0x80000000 != 0 || len(frame.Data) >= 0x0f000000 {
 		return &Error{InvalidDataFrame, frame.StreamId}
diff --git a/src/pkg/exp/sql/convert.go b/src/pkg/exp/sql/convert.go
index a35e0be9cb..b1feef0eb8 100644
--- a/src/pkg/exp/sql/convert.go
+++ b/src/pkg/exp/sql/convert.go
@@ -7,8 +7,8 @@
 package sql
 
 import (
+	"errors"
 	"fmt"
-	"os"
 	"reflect"
 	"strconv"
 )
@@ -16,7 +16,7 @@ import (
 // convertAssign copies to dest the value in src, converting it if possible.
 // An error is returned if the copy would result in loss of information.
 // dest should be a pointer type.
-func convertAssign(dest, src interface{}) os.Error {
+func convertAssign(dest, src interface{}) error {
 	// Common cases, without reflect.  Fall through.
 	switch s := src.(type) {
 	case string:
@@ -56,7 +56,7 @@ func convertAssign(dest, src interface{}) os.Error {
 
 	dpv := reflect.ValueOf(dest)
 	if dpv.Kind() != reflect.Ptr {
-		return os.NewError("destination not a pointer")
+		return errors.New("destination not a pointer")
 	}
 
 	dv := reflect.Indirect(dpv)
diff --git a/src/pkg/exp/sql/convert_test.go b/src/pkg/exp/sql/convert_test.go
index 849991868e..f85ed99978 100644
--- a/src/pkg/exp/sql/convert_test.go
+++ b/src/pkg/exp/sql/convert_test.go
@@ -68,7 +68,7 @@ func TestConversions(t *testing.T) {
 		err := convertAssign(ct.d, ct.s)
 		errstr := ""
 		if err != nil {
-			errstr = err.String()
+			errstr = err.Error()
 		}
 		errf := func(format string, args ...interface{}) {
 			base := fmt.Sprintf("convertAssign #%d: for %v (%T) -> %T, ", n, ct.s, ct.s, ct.d)
diff --git a/src/pkg/exp/sql/driver/driver.go b/src/pkg/exp/sql/driver/driver.go
index 7508b19fa1..52714e817a 100644
--- a/src/pkg/exp/sql/driver/driver.go
+++ b/src/pkg/exp/sql/driver/driver.go
@@ -19,9 +19,7 @@
 //
 package driver
 
-import (
-	"os"
-)
+import "errors"
 
 // Driver is the interface that must be implemented by a database
 // driver.
@@ -31,7 +29,7 @@ type Driver interface {
 	//
 	// The returned connection is only used by one goroutine at a
 	// time.
-	Open(name string) (Conn, os.Error)
+	Open(name string) (Conn, error)
 }
 
 // Execer is an optional interface that may be implemented by a Driver
@@ -48,7 +46,7 @@ type Driver interface {
 //
 // All arguments are of a subset type as defined in the package docs.
 type Execer interface {
-	Exec(query string, args []interface{}) (Result, os.Error)
+	Exec(query string, args []interface{}) (Result, error)
 }
 
 // Conn is a connection to a database. It is not used concurrently
@@ -57,16 +55,16 @@ type Execer interface {
 // Conn is assumed to be stateful.
 type Conn interface {
 	// Prepare returns a prepared statement, bound to this connection.
-	Prepare(query string) (Stmt, os.Error)
+	Prepare(query string) (Stmt, error)
 
 	// Close invalidates and potentially stops any current
 	// prepared statements and transactions, marking this
 	// connection as no longer in use.  The driver may cache or
 	// close its underlying connection to its database.
-	Close() os.Error
+	Close() error
 
 	// Begin starts and returns a new transaction.
-	Begin() (Tx, os.Error)
+	Begin() (Tx, error)
 }
 
 // Result is the result of a query execution.
@@ -74,18 +72,18 @@ type Result interface {
 	// LastInsertId returns the database's auto-generated ID
 	// after, for example, an INSERT into a table with primary
 	// key.
-	LastInsertId() (int64, os.Error)
+	LastInsertId() (int64, error)
 
 	// RowsAffected returns the number of rows affected by the
 	// query.
-	RowsAffected() (int64, os.Error)
+	RowsAffected() (int64, error)
 }
 
 // Stmt is a prepared statement. It is bound to a Conn and not
 // used by multiple goroutines concurrently.
 type Stmt interface {
 	// Close closes the statement.
-	Close() os.Error
+	Close() error
 
 	// NumInput returns the number of placeholder parameters.
 	NumInput() int
@@ -93,11 +91,11 @@ type Stmt interface {
 	// Exec executes a query that doesn't return rows, such
 	// as an INSERT or UPDATE.  The args are all of a subset
 	// type as defined above.
-	Exec(args []interface{}) (Result, os.Error)
+	Exec(args []interface{}) (Result, error)
 
 	// Exec executes a query that may return rows, such as a
 	// SELECT.  The args of all of a subset type as defined above.
-	Query(args []interface{}) (Rows, os.Error)
+	Query(args []interface{}) (Rows, error)
 }
 
 // ColumnConverter may be optionally implemented by Stmt if the
@@ -120,7 +118,7 @@ type Rows interface {
 	Columns() []string
 
 	// Close closes the rows iterator.
-	Close() os.Error
+	Close() error
 
 	// Next is called to populate the next row of data into
 	// the provided slice. The provided slice will be the same
@@ -129,13 +127,13 @@ type Rows interface {
 	// The dest slice may be populated with only with values
 	// of subset types defined above, but excluding string.
 	// All string values must be converted to []byte.
-	Next(dest []interface{}) os.Error
+	Next(dest []interface{}) error
 }
 
 // Tx is a transaction.
 type Tx interface {
-	Commit() os.Error
-	Rollback() os.Error
+	Commit() error
+	Rollback() error
 }
 
 // RowsAffected implements Result for an INSERT or UPDATE operation
@@ -144,11 +142,11 @@ type RowsAffected int64
 
 var _ Result = RowsAffected(0)
 
-func (RowsAffected) LastInsertId() (int64, os.Error) {
-	return 0, os.NewError("no LastInsertId available")
+func (RowsAffected) LastInsertId() (int64, error) {
+	return 0, errors.New("no LastInsertId available")
 }
 
-func (v RowsAffected) RowsAffected() (int64, os.Error) {
+func (v RowsAffected) RowsAffected() (int64, error) {
 	return int64(v), nil
 }
 
@@ -160,10 +158,10 @@ type ddlSuccess struct{}
 
 var _ Result = ddlSuccess{}
 
-func (ddlSuccess) LastInsertId() (int64, os.Error) {
-	return 0, os.NewError("no LastInsertId available after DDL statement")
+func (ddlSuccess) LastInsertId() (int64, error) {
+	return 0, errors.New("no LastInsertId available after DDL statement")
 }
 
-func (ddlSuccess) RowsAffected() (int64, os.Error) {
-	return 0, os.NewError("no RowsAffected available after DDL statement")
+func (ddlSuccess) RowsAffected() (int64, error) {
+	return 0, errors.New("no RowsAffected available after DDL statement")
 }
diff --git a/src/pkg/exp/sql/driver/types.go b/src/pkg/exp/sql/driver/types.go
index 5521d5389c..9faf32f671 100644
--- a/src/pkg/exp/sql/driver/types.go
+++ b/src/pkg/exp/sql/driver/types.go
@@ -6,7 +6,6 @@ package driver
 
 import (
 	"fmt"
-	"os"
 	"reflect"
 	"strconv"
 )
@@ -14,7 +13,7 @@ import (
 // ValueConverter is the interface providing the ConvertValue method.
 type ValueConverter interface {
 	// ConvertValue converts a value to a restricted subset type.
-	ConvertValue(v interface{}) (interface{}, os.Error)
+	ConvertValue(v interface{}) (interface{}, error)
 }
 
 // Bool is a ValueConverter that converts input values to bools.
@@ -27,7 +26,7 @@ type boolType struct{}
 
 var _ ValueConverter = boolType{}
 
-func (boolType) ConvertValue(v interface{}) (interface{}, os.Error) {
+func (boolType) ConvertValue(v interface{}) (interface{}, error) {
 	return nil, fmt.Errorf("TODO(bradfitz): bool conversions")
 }
 
@@ -39,7 +38,7 @@ type int32Type struct{}
 
 var _ ValueConverter = int32Type{}
 
-func (int32Type) ConvertValue(v interface{}) (interface{}, os.Error) {
+func (int32Type) ConvertValue(v interface{}) (interface{}, error) {
 	rv := reflect.ValueOf(v)
 	switch rv.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
@@ -72,7 +71,7 @@ var String stringType
 
 type stringType struct{}
 
-func (stringType) ConvertValue(v interface{}) (interface{}, os.Error) {
+func (stringType) ConvertValue(v interface{}) (interface{}, error) {
 	switch v.(type) {
 	case string, []byte:
 		return v, nil
@@ -137,7 +136,7 @@ type defaultConverter struct{}
 
 var _ ValueConverter = defaultConverter{}
 
-func (defaultConverter) ConvertValue(v interface{}) (interface{}, os.Error) {
+func (defaultConverter) ConvertValue(v interface{}) (interface{}, error) {
 	if IsParameterSubsetType(v) {
 		return v, nil
 	}
diff --git a/src/pkg/exp/sql/fakedb_test.go b/src/pkg/exp/sql/fakedb_test.go
index c906185e58..289294bee2 100644
--- a/src/pkg/exp/sql/fakedb_test.go
+++ b/src/pkg/exp/sql/fakedb_test.go
@@ -5,9 +5,10 @@
 package sql
 
 import (
+	"errors"
 	"fmt"
+	"io"
 	"log"
-	"os"
 	"strconv"
 	"strings"
 	"sync"
@@ -108,7 +109,7 @@ func init() {
 // Supports dsn forms:
 //    <dbname>
 //    <dbname>;wipe
-func (d *fakeDriver) Open(dsn string) (driver.Conn, os.Error) {
+func (d *fakeDriver) Open(dsn string) (driver.Conn, error) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 	d.openCount++
@@ -117,7 +118,7 @@ func (d *fakeDriver) Open(dsn string) (driver.Conn, os.Error) {
 	}
 	parts := strings.Split(dsn, ";")
 	if len(parts) < 1 {
-		return nil, os.NewError("fakedb: no database name")
+		return nil, errors.New("fakedb: no database name")
 	}
 	name := parts[0]
 	db, ok := d.dbs[name]
@@ -134,7 +135,7 @@ func (db *fakeDB) wipe() {
 	db.tables = nil
 }
 
-func (db *fakeDB) createTable(name string, columnNames, columnTypes []string) os.Error {
+func (db *fakeDB) createTable(name string, columnNames, columnTypes []string) error {
 	db.mu.Lock()
 	defer db.mu.Unlock()
 	if db.tables == nil {
@@ -175,33 +176,33 @@ func (db *fakeDB) columnType(table, column string) (typ string, ok bool) {
 	return "", false
 }
 
-func (c *fakeConn) Begin() (driver.Tx, os.Error) {
+func (c *fakeConn) Begin() (driver.Tx, error) {
 	if c.currTx != nil {
-		return nil, os.NewError("already in a transaction")
+		return nil, errors.New("already in a transaction")
 	}
 	c.currTx = &fakeTx{c: c}
 	return c.currTx, nil
 }
 
-func (c *fakeConn) Close() os.Error {
+func (c *fakeConn) Close() error {
 	if c.currTx != nil {
-		return os.NewError("can't close; in a Transaction")
+		return errors.New("can't close; in a Transaction")
 	}
 	if c.db == nil {
-		return os.NewError("can't close; already closed")
+		return errors.New("can't close; already closed")
 	}
 	c.db = nil
 	return nil
 }
 
-func errf(msg string, args ...interface{}) os.Error {
-	return os.NewError("fakedb: " + fmt.Sprintf(msg, args...))
+func errf(msg string, args ...interface{}) error {
+	return errors.New("fakedb: " + fmt.Sprintf(msg, args...))
 }
 
 // parts are table|selectCol1,selectCol2|whereCol=?,whereCol2=?
 // (note that where where columns must always contain ? marks,
 //  just a limitation for fakedb)
-func (c *fakeConn) prepareSelect(stmt *fakeStmt, parts []string) (driver.Stmt, os.Error) {
+func (c *fakeConn) prepareSelect(stmt *fakeStmt, parts []string) (driver.Stmt, error) {
 	if len(parts) != 3 {
 		return nil, errf("invalid SELECT syntax with %d parts; want 3", len(parts))
 	}
@@ -228,7 +229,7 @@ func (c *fakeConn) prepareSelect(stmt *fakeStmt, parts []string) (driver.Stmt, o
 }
 
 // parts are table|col=type,col2=type2
-func (c *fakeConn) prepareCreate(stmt *fakeStmt, parts []string) (driver.Stmt, os.Error) {
+func (c *fakeConn) prepareCreate(stmt *fakeStmt, parts []string) (driver.Stmt, error) {
 	if len(parts) != 2 {
 		return nil, errf("invalid CREATE syntax with %d parts; want 2", len(parts))
 	}
@@ -245,7 +246,7 @@ func (c *fakeConn) prepareCreate(stmt *fakeStmt, parts []string) (driver.Stmt, o
 }
 
 // parts are table|col=?,col2=val
-func (c *fakeConn) prepareInsert(stmt *fakeStmt, parts []string) (driver.Stmt, os.Error) {
+func (c *fakeConn) prepareInsert(stmt *fakeStmt, parts []string) (driver.Stmt, error) {
 	if len(parts) != 2 {
 		return nil, errf("invalid INSERT syntax with %d parts; want 2", len(parts))
 	}
@@ -287,7 +288,7 @@ func (c *fakeConn) prepareInsert(stmt *fakeStmt, parts []string) (driver.Stmt, o
 	return stmt, nil
 }
 
-func (c *fakeConn) Prepare(query string) (driver.Stmt, os.Error) {
+func (c *fakeConn) Prepare(query string) (driver.Stmt, error) {
 	if c.db == nil {
 		panic("nil c.db; conn = " + fmt.Sprintf("%#v", c))
 	}
@@ -317,11 +318,11 @@ func (s *fakeStmt) ColumnConverter(idx int) driver.ValueConverter {
 	return s.placeholderConverter[idx]
 }
 
-func (s *fakeStmt) Close() os.Error {
+func (s *fakeStmt) Close() error {
 	return nil
 }
 
-func (s *fakeStmt) Exec(args []interface{}) (driver.Result, os.Error) {
+func (s *fakeStmt) Exec(args []interface{}) (driver.Result, error) {
 	db := s.c.db
 	switch s.cmd {
 	case "WIPE":
@@ -339,7 +340,7 @@ func (s *fakeStmt) Exec(args []interface{}) (driver.Result, os.Error) {
 	return nil, fmt.Errorf("unimplemented statement Exec command type of %q", s.cmd)
 }
 
-func (s *fakeStmt) execInsert(args []interface{}) (driver.Result, os.Error) {
+func (s *fakeStmt) execInsert(args []interface{}) (driver.Result, error) {
 	db := s.c.db
 	if len(args) != s.placeholders {
 		panic("error in pkg db; should only get here if size is correct")
@@ -375,7 +376,7 @@ func (s *fakeStmt) execInsert(args []interface{}) (driver.Result, os.Error) {
 	return driver.RowsAffected(1), nil
 }
 
-func (s *fakeStmt) Query(args []interface{}) (driver.Rows, os.Error) {
+func (s *fakeStmt) Query(args []interface{}) (driver.Rows, error) {
 	db := s.c.db
 	if len(args) != s.placeholders {
 		panic("error in pkg db; should only get here if size is correct")
@@ -438,12 +439,12 @@ func (s *fakeStmt) NumInput() int {
 	return s.placeholders
 }
 
-func (tx *fakeTx) Commit() os.Error {
+func (tx *fakeTx) Commit() error {
 	tx.c.currTx = nil
 	return nil
 }
 
-func (tx *fakeTx) Rollback() os.Error {
+func (tx *fakeTx) Rollback() error {
 	tx.c.currTx = nil
 	return nil
 }
@@ -455,7 +456,7 @@ type rowsCursor struct {
 	closed bool
 }
 
-func (rc *rowsCursor) Close() os.Error {
+func (rc *rowsCursor) Close() error {
 	rc.closed = true
 	return nil
 }
@@ -464,13 +465,13 @@ func (rc *rowsCursor) Columns() []string {
 	return rc.cols
 }
 
-func (rc *rowsCursor) Next(dest []interface{}) os.Error {
+func (rc *rowsCursor) Next(dest []interface{}) error {
 	if rc.closed {
-		return os.NewError("fakedb: cursor is closed")
+		return errors.New("fakedb: cursor is closed")
 	}
 	rc.pos++
 	if rc.pos >= len(rc.rows) {
-		return os.EOF // per interface spec
+		return io.EOF // per interface spec
 	}
 	for i, v := range rc.rows[rc.pos].cols {
 		// TODO(bradfitz): convert to subset types? naah, I
diff --git a/src/pkg/exp/sql/sql.go b/src/pkg/exp/sql/sql.go
index 7f0e0b2842..4f1c539127 100644
--- a/src/pkg/exp/sql/sql.go
+++ b/src/pkg/exp/sql/sql.go
@@ -7,8 +7,9 @@
 package sql
 
 import (
+	"errors"
 	"fmt"
-	"os"
+	"io"
 	"runtime"
 	"sync"
 
@@ -50,7 +51,7 @@ type NullableString struct {
 }
 
 // ScanInto implements the ScannerInto interface.
-func (ms *NullableString) ScanInto(value interface{}) os.Error {
+func (ms *NullableString) ScanInto(value interface{}) error {
 	if value == nil {
 		ms.String, ms.Valid = "", false
 		return nil
@@ -74,13 +75,13 @@ type ScannerInto interface {
 	//
 	// An error should be returned if the value can not be stored
 	// without loss of information.
-	ScanInto(value interface{}) os.Error
+	ScanInto(value interface{}) error
 }
 
 // ErrNoRows is returned by Scan when QueryRow doesn't return a
 // row. In such a case, QueryRow returns a placeholder *Row value that
 // defers this error until a Scan.
-var ErrNoRows = os.NewError("db: no rows in result set")
+var ErrNoRows = errors.New("db: no rows in result set")
 
 // DB is a database handle. It's safe for concurrent use by multiple
 // goroutines.
@@ -98,7 +99,7 @@ type DB struct {
 //
 // Most users will open a database via a driver-specific connection
 // helper function that returns a *DB.
-func Open(driverName, dataSourceName string) (*DB, os.Error) {
+func Open(driverName, dataSourceName string) (*DB, error) {
 	driver, ok := drivers[driverName]
 	if !ok {
 		return nil, fmt.Errorf("db: unknown driver %q (forgotten import?)", driverName)
@@ -114,7 +115,7 @@ func (db *DB) maxIdleConns() int {
 }
 
 // conn returns a newly-opened or cached driver.Conn
-func (db *DB) conn() (driver.Conn, os.Error) {
+func (db *DB) conn() (driver.Conn, error) {
 	db.mu.Lock()
 	if n := len(db.freeConn); n > 0 {
 		conn := db.freeConn[n-1]
@@ -154,7 +155,7 @@ func (db *DB) closeConn(c driver.Conn) {
 }
 
 // Prepare creates a prepared statement for later execution.
-func (db *DB) Prepare(query string) (*Stmt, os.Error) {
+func (db *DB) Prepare(query string) (*Stmt, error) {
 	// TODO: check if db.driver supports an optional
 	// driver.Preparer interface and call that instead, if so,
 	// otherwise we make a prepared statement that's bound
@@ -179,7 +180,7 @@ func (db *DB) Prepare(query string) (*Stmt, os.Error) {
 }
 
 // Exec executes a query without returning any rows.
-func (db *DB) Exec(query string, args ...interface{}) (Result, os.Error) {
+func (db *DB) Exec(query string, args ...interface{}) (Result, error) {
 	// Optional fast path, if the driver implements driver.Execer.
 	if execer, ok := db.driver.(driver.Execer); ok {
 		resi, err := execer.Exec(query, args)
@@ -218,7 +219,7 @@ func (db *DB) Exec(query string, args ...interface{}) (Result, os.Error) {
 }
 
 // Query executes a query that returns rows, typically a SELECT.
-func (db *DB) Query(query string, args ...interface{}) (*Rows, os.Error) {
+func (db *DB) Query(query string, args ...interface{}) (*Rows, error) {
 	stmt, err := db.Prepare(query)
 	if err != nil {
 		return nil, err
@@ -240,7 +241,7 @@ func (db *DB) QueryRow(query string, args ...interface{}) *Row {
 
 // Begin starts a transaction.  The isolation level is dependent on
 // the driver.
-func (db *DB) Begin() (*Tx, os.Error) {
+func (db *DB) Begin() (*Tx, error) {
 	// TODO(bradfitz): add another method for beginning a transaction
 	// at a specific isolation level.
 	panic(todo())
@@ -257,17 +258,17 @@ type Tx struct {
 }
 
 // Commit commits the transaction.
-func (tx *Tx) Commit() os.Error {
+func (tx *Tx) Commit() error {
 	panic(todo())
 }
 
 // Rollback aborts the transaction.
-func (tx *Tx) Rollback() os.Error {
+func (tx *Tx) Rollback() error {
 	panic(todo())
 }
 
 // Prepare creates a prepared statement.
-func (tx *Tx) Prepare(query string) (*Stmt, os.Error) {
+func (tx *Tx) Prepare(query string) (*Stmt, error) {
 	panic(todo())
 }
 
@@ -278,7 +279,7 @@ func (tx *Tx) Exec(query string, args ...interface{}) {
 }
 
 // Query executes a query that returns rows, typically a SELECT.
-func (tx *Tx) Query(query string, args ...interface{}) (*Rows, os.Error) {
+func (tx *Tx) Query(query string, args ...interface{}) (*Rows, error) {
 	panic(todo())
 }
 
@@ -313,7 +314,7 @@ func todo() string {
 
 // Exec executes a prepared statement with the given arguments and
 // returns a Result summarizing the effect of the statement.
-func (s *Stmt) Exec(args ...interface{}) (Result, os.Error) {
+func (s *Stmt) Exec(args ...interface{}) (Result, error) {
 	ci, si, err := s.connStmt()
 	if err != nil {
 		return nil, err
@@ -352,10 +353,10 @@ func (s *Stmt) Exec(args ...interface{}) (Result, os.Error) {
 	return result{resi}, nil
 }
 
-func (s *Stmt) connStmt(args ...interface{}) (driver.Conn, driver.Stmt, os.Error) {
+func (s *Stmt) connStmt(args ...interface{}) (driver.Conn, driver.Stmt, error) {
 	s.mu.Lock()
 	if s.closed {
-		return nil, nil, os.NewError("db: statement is closed")
+		return nil, nil, errors.New("db: statement is closed")
 	}
 	var cs connStmt
 	match := false
@@ -391,7 +392,7 @@ func (s *Stmt) connStmt(args ...interface{}) (driver.Conn, driver.Stmt, os.Error
 
 // Query executes a prepared query statement with the given arguments
 // and returns the query results as a *Rows.
-func (s *Stmt) Query(args ...interface{}) (*Rows, os.Error) {
+func (s *Stmt) Query(args ...interface{}) (*Rows, error) {
 	ci, si, err := s.connStmt(args...)
 	if err != nil {
 		return nil, err
@@ -433,7 +434,7 @@ func (s *Stmt) QueryRow(args ...interface{}) *Row {
 }
 
 // Close closes the statement.
-func (s *Stmt) Close() os.Error {
+func (s *Stmt) Close() error {
 	s.mu.Lock()
 	defer s.mu.Unlock() // TODO(bradfitz): move this unlock after 'closed = true'?
 	if s.closed {
@@ -473,7 +474,7 @@ type Rows struct {
 
 	closed   bool
 	lastcols []interface{}
-	lasterr  os.Error
+	lasterr  error
 }
 
 // Next prepares the next result row for reading with the Scan method.
@@ -495,8 +496,8 @@ func (rs *Rows) Next() bool {
 }
 
 // Error returns the error, if any, that was encountered during iteration.
-func (rs *Rows) Error() os.Error {
-	if rs.lasterr == os.EOF {
+func (rs *Rows) Error() error {
+	if rs.lasterr == io.EOF {
 		return nil
 	}
 	return rs.lasterr
@@ -506,15 +507,15 @@ func (rs *Rows) Error() os.Error {
 // at by dest. If dest contains pointers to []byte, the slices should
 // not be modified and should only be considered valid until the next
 // call to Next or Scan.
-func (rs *Rows) Scan(dest ...interface{}) os.Error {
+func (rs *Rows) Scan(dest ...interface{}) error {
 	if rs.closed {
-		return os.NewError("db: Rows closed")
+		return errors.New("db: Rows closed")
 	}
 	if rs.lasterr != nil {
 		return rs.lasterr
 	}
 	if rs.lastcols == nil {
-		return os.NewError("db: Scan called without calling Next")
+		return errors.New("db: Scan called without calling Next")
 	}
 	if len(dest) != len(rs.lastcols) {
 		return fmt.Errorf("db: expected %d destination arguments in Scan, not %d", len(rs.lastcols), len(dest))
@@ -531,7 +532,7 @@ func (rs *Rows) Scan(dest ...interface{}) os.Error {
 // Close closes the Rows, preventing further enumeration. If the
 // end is encountered, the Rows are closed automatically. Close
 // is idempotent.
-func (rs *Rows) Close() os.Error {
+func (rs *Rows) Close() error {
 	if rs.closed {
 		return nil
 	}
@@ -544,7 +545,7 @@ func (rs *Rows) Close() os.Error {
 // Row is the result of calling QueryRow to select a single row.
 type Row struct {
 	// One of these two will be non-nil:
-	err  os.Error // deferred error for easy chaining
+	err  error // deferred error for easy chaining
 	rows *Rows
 }
 
@@ -556,7 +557,7 @@ type Row struct {
 // If dest contains pointers to []byte, the slices should not be
 // modified and should only be considered valid until the next call to
 // Next or Scan.
-func (r *Row) Scan(dest ...interface{}) os.Error {
+func (r *Row) Scan(dest ...interface{}) error {
 	if r.err != nil {
 		return r.err
 	}
@@ -569,8 +570,8 @@ func (r *Row) Scan(dest ...interface{}) os.Error {
 
 // A Result summarizes an executed SQL command.
 type Result interface {
-	LastInsertId() (int64, os.Error)
-	RowsAffected() (int64, os.Error)
+	LastInsertId() (int64, error)
+	RowsAffected() (int64, error)
 }
 
 type result struct {
diff --git a/src/pkg/exp/sql/sql_test.go b/src/pkg/exp/sql/sql_test.go
index eaa0a90356..eb1bb58966 100644
--- a/src/pkg/exp/sql/sql_test.go
+++ b/src/pkg/exp/sql/sql_test.go
@@ -40,7 +40,7 @@ func TestQuery(t *testing.T) {
 	var age int
 
 	err := db.QueryRow("SELECT|people|age,name|age=?", 3).Scan(&age)
-	if err == nil || !strings.Contains(err.String(), "expected 2 destination arguments") {
+	if err == nil || !strings.Contains(err.Error(), "expected 2 destination arguments") {
 		t.Errorf("expected error from wrong number of arguments; actually got: %v", err)
 	}
 
@@ -99,7 +99,7 @@ func TestBogusPreboundParameters(t *testing.T) {
 	if err == nil {
 		t.Fatalf("expected error")
 	}
-	if err.String() != `fakedb: invalid conversion to int32 from "bogusconversion"` {
+	if err.Error() != `fakedb: invalid conversion to int32 from "bogusconversion"` {
 		t.Errorf("unexpected error: %v", err)
 	}
 }
@@ -135,7 +135,7 @@ func TestDb(t *testing.T) {
 		_, err := stmt.Exec(et.args...)
 		errStr := ""
 		if err != nil {
-			errStr = err.String()
+			errStr = err.Error()
 		}
 		if errStr != et.wantErr {
 			t.Errorf("stmt.Execute #%d: for %v, got error %q, want error %q",
diff --git a/src/pkg/exp/ssh/channel.go b/src/pkg/exp/ssh/channel.go
index f69b735fd4..428e71c806 100644
--- a/src/pkg/exp/ssh/channel.go
+++ b/src/pkg/exp/ssh/channel.go
@@ -5,7 +5,8 @@
 package ssh
 
 import (
-	"os"
+	"errors"
+	"io"
 	"sync"
 )
 
@@ -13,19 +14,19 @@ import (
 // SSH connection.
 type Channel interface {
 	// Accept accepts the channel creation request.
-	Accept() os.Error
+	Accept() error
 	// Reject rejects the channel creation request. After calling this, no
 	// other methods on the Channel may be called. If they are then the
 	// peer is likely to signal a protocol error and drop the connection.
-	Reject(reason RejectionReason, message string) os.Error
+	Reject(reason RejectionReason, message string) error
 
 	// Read may return a ChannelRequest as an os.Error.
-	Read(data []byte) (int, os.Error)
-	Write(data []byte) (int, os.Error)
-	Close() os.Error
+	Read(data []byte) (int, error)
+	Write(data []byte) (int, error)
+	Close() error
 
 	// AckRequest either sends an ack or nack to the channel request.
-	AckRequest(ok bool) os.Error
+	AckRequest(ok bool) error
 
 	// ChannelType returns the type of the channel, as supplied by the
 	// client.
@@ -43,7 +44,7 @@ type ChannelRequest struct {
 	Payload   []byte
 }
 
-func (c ChannelRequest) String() string {
+func (c ChannelRequest) Error() string {
 	return "channel request received"
 }
 
@@ -72,7 +73,7 @@ type channel struct {
 	myId, theirId         uint32
 	myWindow, theirWindow uint32
 	maxPacketSize         uint32
-	err                   os.Error
+	err                   error
 
 	pendingRequests []ChannelRequest
 	pendingData     []byte
@@ -83,7 +84,7 @@ type channel struct {
 	cond *sync.Cond
 }
 
-func (c *channel) Accept() os.Error {
+func (c *channel) Accept() error {
 	c.serverConn.lock.Lock()
 	defer c.serverConn.lock.Unlock()
 
@@ -100,7 +101,7 @@ func (c *channel) Accept() os.Error {
 	return c.serverConn.writePacket(marshal(msgChannelOpenConfirm, confirm))
 }
 
-func (c *channel) Reject(reason RejectionReason, message string) os.Error {
+func (c *channel) Reject(reason RejectionReason, message string) error {
 	c.serverConn.lock.Lock()
 	defer c.serverConn.lock.Unlock()
 
@@ -167,7 +168,7 @@ func (c *channel) handleData(data []byte) {
 	c.cond.Signal()
 }
 
-func (c *channel) Read(data []byte) (n int, err os.Error) {
+func (c *channel) Read(data []byte) (n int, err error) {
 	c.lock.Lock()
 	defer c.lock.Unlock()
 
@@ -187,7 +188,7 @@ func (c *channel) Read(data []byte) (n int, err os.Error) {
 
 	for {
 		if c.theySentEOF || c.theyClosed || c.dead {
-			return 0, os.EOF
+			return 0, io.EOF
 		}
 
 		if len(c.pendingRequests) > 0 {
@@ -223,11 +224,11 @@ func (c *channel) Read(data []byte) (n int, err os.Error) {
 	panic("unreachable")
 }
 
-func (c *channel) Write(data []byte) (n int, err os.Error) {
+func (c *channel) Write(data []byte) (n int, err error) {
 	for len(data) > 0 {
 		c.lock.Lock()
 		if c.dead || c.weClosed {
-			return 0, os.EOF
+			return 0, io.EOF
 		}
 
 		if c.theirWindow == 0 {
@@ -267,7 +268,7 @@ func (c *channel) Write(data []byte) (n int, err os.Error) {
 	return
 }
 
-func (c *channel) Close() os.Error {
+func (c *channel) Close() error {
 	c.serverConn.lock.Lock()
 	defer c.serverConn.lock.Unlock()
 
@@ -276,7 +277,7 @@ func (c *channel) Close() os.Error {
 	}
 
 	if c.weClosed {
-		return os.NewError("ssh: channel already closed")
+		return errors.New("ssh: channel already closed")
 	}
 	c.weClosed = true
 
@@ -286,7 +287,7 @@ func (c *channel) Close() os.Error {
 	return c.serverConn.writePacket(marshal(msgChannelClose, closeMsg))
 }
 
-func (c *channel) AckRequest(ok bool) os.Error {
+func (c *channel) AckRequest(ok bool) error {
 	c.serverConn.lock.Lock()
 	defer c.serverConn.lock.Unlock()
 
diff --git a/src/pkg/exp/ssh/client.go b/src/pkg/exp/ssh/client.go
index fe76db16c4..345e707b33 100644
--- a/src/pkg/exp/ssh/client.go
+++ b/src/pkg/exp/ssh/client.go
@@ -8,9 +8,9 @@ import (
 	"big"
 	"crypto"
 	"crypto/rand"
+	"errors"
 	"fmt"
 	"io"
-	"os"
 	"net"
 	"sync"
 )
@@ -26,7 +26,7 @@ type ClientConn struct {
 }
 
 // Client returns a new SSH client connection using c as the underlying transport.
-func Client(c net.Conn, config *ClientConfig) (*ClientConn, os.Error) {
+func Client(c net.Conn, config *ClientConfig) (*ClientConn, error) {
 	conn := &ClientConn{
 		transport: newTransport(c, config.rand()),
 		config:    config,
@@ -44,7 +44,7 @@ func Client(c net.Conn, config *ClientConfig) (*ClientConn, os.Error) {
 }
 
 // handshake performs the client side key exchange. See RFC 4253 Section 7.
-func (c *ClientConn) handshake() os.Error {
+func (c *ClientConn) handshake() error {
 	var magics handshakeMagics
 
 	if _, err := c.Write(clientVersion); err != nil {
@@ -91,7 +91,7 @@ func (c *ClientConn) handshake() os.Error {
 
 	kexAlgo, hostKeyAlgo, ok := findAgreedAlgorithms(c.transport, &clientKexInit, &serverKexInit)
 	if !ok {
-		return os.NewError("ssh: no common algorithms")
+		return errors.New("ssh: no common algorithms")
 	}
 
 	if serverKexInit.FirstKexFollows && kexAlgo != serverKexInit.KexAlgos[0] {
@@ -133,7 +133,7 @@ func (c *ClientConn) handshake() os.Error {
 
 // authenticate authenticates with the remote server. See RFC 4252. 
 // Only "password" authentication is supported.
-func (c *ClientConn) authenticate() os.Error {
+func (c *ClientConn) authenticate() error {
 	if err := c.writePacket(marshal(msgServiceRequest, serviceRequestMsg{serviceUserAuth})); err != nil {
 		return err
 	}
@@ -166,7 +166,7 @@ func (c *ClientConn) authenticate() os.Error {
 	return nil
 }
 
-func (c *ClientConn) sendUserAuthReq(method string) os.Error {
+func (c *ClientConn) sendUserAuthReq(method string) error {
 	length := stringLength([]byte(c.config.Password)) + 1
 	payload := make([]byte, length)
 	// always false for password auth, see RFC 4252 Section 8.
@@ -183,7 +183,7 @@ func (c *ClientConn) sendUserAuthReq(method string) os.Error {
 
 // kexDH performs Diffie-Hellman key agreement on a ClientConn. The
 // returned values are given the same names as in RFC 4253, section 8.
-func (c *ClientConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handshakeMagics, hostKeyAlgo string) ([]byte, []byte, os.Error) {
+func (c *ClientConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handshakeMagics, hostKeyAlgo string) ([]byte, []byte, error) {
 	x, err := rand.Int(c.config.rand(), group.p)
 	if err != nil {
 		return nil, nil, err
@@ -207,7 +207,7 @@ func (c *ClientConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handsha
 	}
 
 	if kexDHReply.Y.Sign() == 0 || kexDHReply.Y.Cmp(group.p) >= 0 {
-		return nil, nil, os.NewError("server DH parameter out of bounds")
+		return nil, nil, errors.New("server DH parameter out of bounds")
 	}
 
 	kInt := new(big.Int).Exp(kexDHReply.Y, x, group.p)
@@ -230,7 +230,7 @@ func (c *ClientConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handsha
 
 // openChan opens a new client channel. The most common session type is "session". 
 // The full set of valid session types are listed in RFC 4250 4.9.1.
-func (c *ClientConn) openChan(typ string) (*clientChan, os.Error) {
+func (c *ClientConn) openChan(typ string) (*clientChan, error) {
 	ch := c.newChan(c.transport)
 	if err := c.writePacket(marshal(msgChannelOpen, channelOpenMsg{
 		ChanType:      typ,
@@ -247,10 +247,10 @@ func (c *ClientConn) openChan(typ string) (*clientChan, os.Error) {
 		ch.peersId = msg.MyId
 	case *channelOpenFailureMsg:
 		c.chanlist.remove(ch.id)
-		return nil, os.NewError(msg.Message)
+		return nil, errors.New(msg.Message)
 	default:
 		c.chanlist.remove(ch.id)
-		return nil, os.NewError("Unexpected packet")
+		return nil, errors.New("Unexpected packet")
 	}
 	return ch, nil
 }
@@ -329,7 +329,7 @@ func (c *ClientConn) mainLoop() {
 
 // Dial connects to the given network address using net.Dial and 
 // then initiates a SSH handshake, returning the resulting client connection.
-func Dial(network, addr string, config *ClientConfig) (*ClientConn, os.Error) {
+func Dial(network, addr string, config *ClientConfig) (*ClientConn, error) {
 	conn, err := net.Dial(network, addr)
 	if err != nil {
 		return nil, err
@@ -382,13 +382,13 @@ func newClientChan(t *transport, id uint32) *clientChan {
 }
 
 // Close closes the channel. This does not close the underlying connection.
-func (c *clientChan) Close() os.Error {
+func (c *clientChan) Close() error {
 	return c.writePacket(marshal(msgChannelClose, channelCloseMsg{
 		PeersId: c.id,
 	}))
 }
 
-func (c *clientChan) sendChanReq(req channelRequestMsg) os.Error {
+func (c *clientChan) sendChanReq(req channelRequestMsg) error {
 	if err := c.writePacket(marshal(msgChannelRequest, req)); err != nil {
 		return err
 	}
@@ -447,12 +447,12 @@ type chanWriter struct {
 }
 
 // Write writes data to the remote process's standard input.
-func (w *chanWriter) Write(data []byte) (n int, err os.Error) {
+func (w *chanWriter) Write(data []byte) (n int, err error) {
 	for {
 		if w.rwin == 0 {
 			win, ok := <-w.win
 			if !ok {
-				return 0, os.EOF
+				return 0, io.EOF
 			}
 			w.rwin += win
 			continue
@@ -469,7 +469,7 @@ func (w *chanWriter) Write(data []byte) (n int, err os.Error) {
 	panic("unreachable")
 }
 
-func (w *chanWriter) Close() os.Error {
+func (w *chanWriter) Close() error {
 	return w.writePacket(marshal(msgChannelEOF, channelEOFMsg{w.id}))
 }
 
@@ -485,7 +485,7 @@ type chanReader struct {
 }
 
 // Read reads data from the remote process's stdout or stderr.
-func (r *chanReader) Read(data []byte) (int, os.Error) {
+func (r *chanReader) Read(data []byte) (int, error) {
 	var ok bool
 	for {
 		if len(r.buf) > 0 {
@@ -499,12 +499,12 @@ func (r *chanReader) Read(data []byte) (int, os.Error) {
 		}
 		r.buf, ok = <-r.data
 		if !ok {
-			return 0, os.EOF
+			return 0, io.EOF
 		}
 	}
 	panic("unreachable")
 }
 
-func (r *chanReader) Close() os.Error {
+func (r *chanReader) Close() error {
 	return r.writePacket(marshal(msgChannelEOF, channelEOFMsg{r.id}))
 }
diff --git a/src/pkg/exp/ssh/common.go b/src/pkg/exp/ssh/common.go
index 739bd2f9c5..f68c353a39 100644
--- a/src/pkg/exp/ssh/common.go
+++ b/src/pkg/exp/ssh/common.go
@@ -53,7 +53,7 @@ type UnexpectedMessageError struct {
 	expected, got uint8
 }
 
-func (u UnexpectedMessageError) String() string {
+func (u UnexpectedMessageError) Error() string {
 	return "ssh: unexpected message type " + strconv.Itoa(int(u.got)) + " (expected " + strconv.Itoa(int(u.expected)) + ")"
 }
 
@@ -62,7 +62,7 @@ type ParseError struct {
 	msgType uint8
 }
 
-func (p ParseError) String() string {
+func (p ParseError) Error() string {
 	return "ssh: parse error in message type " + strconv.Itoa(int(p.msgType))
 }
 
diff --git a/src/pkg/exp/ssh/messages.go b/src/pkg/exp/ssh/messages.go
index 5f2c447142..5eae181872 100644
--- a/src/pkg/exp/ssh/messages.go
+++ b/src/pkg/exp/ssh/messages.go
@@ -8,7 +8,6 @@ import (
 	"big"
 	"bytes"
 	"io"
-	"os"
 	"reflect"
 )
 
@@ -192,7 +191,7 @@ type userAuthPubKeyOkMsg struct {
 // unmarshal parses the SSH wire data in packet into out using reflection.
 // expectedType is the expected SSH message type. It either returns nil on
 // success, or a ParseError or UnexpectedMessageError on error.
-func unmarshal(out interface{}, packet []byte, expectedType uint8) os.Error {
+func unmarshal(out interface{}, packet []byte, expectedType uint8) error {
 	if len(packet) == 0 {
 		return ParseError{expectedType}
 	}
diff --git a/src/pkg/exp/ssh/server.go b/src/pkg/exp/ssh/server.go
index 0dd24ecd6e..2ae8079d2d 100644
--- a/src/pkg/exp/ssh/server.go
+++ b/src/pkg/exp/ssh/server.go
@@ -12,9 +12,9 @@ import (
 	"crypto/rsa"
 	"crypto/x509"
 	"encoding/pem"
+	"errors"
 	"io"
 	"net"
-	"os"
 	"sync"
 )
 
@@ -53,12 +53,12 @@ func (c *ServerConfig) rand() io.Reader {
 // private key configured in order to accept connections. The private key must
 // be in the form of a PEM encoded, PKCS#1, RSA private key. The file "id_rsa"
 // typically contains such a key.
-func (s *ServerConfig) SetRSAPrivateKey(pemBytes []byte) os.Error {
+func (s *ServerConfig) SetRSAPrivateKey(pemBytes []byte) error {
 	block, _ := pem.Decode(pemBytes)
 	if block == nil {
-		return os.NewError("ssh: no key found")
+		return errors.New("ssh: no key found")
 	}
-	var err os.Error
+	var err error
 	s.rsa, err = x509.ParsePKCS1PrivateKey(block.Bytes)
 	if err != nil {
 		return err
@@ -140,7 +140,7 @@ type ServerConn struct {
 	// lock protects err and also allows Channels to serialise their writes
 	// to out.
 	lock sync.RWMutex
-	err  os.Error
+	err  error
 
 	// cachedPubKeys contains the cache results of tests for public keys.
 	// Since SSH clients will query whether a public key is acceptable
@@ -162,7 +162,7 @@ func Server(c net.Conn, config *ServerConfig) *ServerConn {
 
 // kexDH performs Diffie-Hellman key agreement on a ServerConnection. The
 // returned values are given the same names as in RFC 4253, section 8.
-func (s *ServerConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handshakeMagics, hostKeyAlgo string) (H, K []byte, err os.Error) {
+func (s *ServerConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handshakeMagics, hostKeyAlgo string) (H, K []byte, err error) {
 	packet, err := s.readPacket()
 	if err != nil {
 		return
@@ -173,7 +173,7 @@ func (s *ServerConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handsha
 	}
 
 	if kexDHInit.X.Sign() == 0 || kexDHInit.X.Cmp(group.p) >= 0 {
-		return nil, nil, os.NewError("client DH parameter out of bounds")
+		return nil, nil, errors.New("client DH parameter out of bounds")
 	}
 
 	y, err := rand.Int(s.config.rand(), group.p)
@@ -189,7 +189,7 @@ func (s *ServerConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handsha
 	case hostAlgoRSA:
 		serializedHostKey = s.config.rsaSerialized
 	default:
-		return nil, nil, os.NewError("internal error")
+		return nil, nil, errors.New("internal error")
 	}
 
 	h := hashFunc.New()
@@ -218,7 +218,7 @@ func (s *ServerConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handsha
 			return
 		}
 	default:
-		return nil, nil, os.NewError("internal error")
+		return nil, nil, errors.New("internal error")
 	}
 
 	serializedSig := serializeRSASignature(sig)
@@ -279,7 +279,7 @@ func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubK
 }
 
 // Handshake performs an SSH transport and client authentication on the given ServerConn.
-func (s *ServerConn) Handshake() os.Error {
+func (s *ServerConn) Handshake() error {
 	var magics handshakeMagics
 	if _, err := s.Write(serverVersion); err != nil {
 		return err
@@ -326,7 +326,7 @@ func (s *ServerConn) Handshake() os.Error {
 
 	kexAlgo, hostKeyAlgo, ok := findAgreedAlgorithms(s.transport, &clientKexInit, &serverKexInit)
 	if !ok {
-		return os.NewError("ssh: no common algorithms")
+		return errors.New("ssh: no common algorithms")
 	}
 
 	if clientKexInit.FirstKexFollows && kexAlgo != clientKexInit.KexAlgos[0] {
@@ -345,7 +345,7 @@ func (s *ServerConn) Handshake() os.Error {
 		dhGroup14Once.Do(initDHGroup14)
 		H, K, err = s.kexDH(dhGroup14, hashFunc, &magics, hostKeyAlgo)
 	default:
-		err = os.NewError("ssh: unexpected key exchange algorithm " + kexAlgo)
+		err = errors.New("ssh: unexpected key exchange algorithm " + kexAlgo)
 	}
 	if err != nil {
 		return err
@@ -374,7 +374,7 @@ func (s *ServerConn) Handshake() os.Error {
 		return err
 	}
 	if serviceRequest.Service != serviceUserAuth {
-		return os.NewError("ssh: requested service '" + serviceRequest.Service + "' before authenticating")
+		return errors.New("ssh: requested service '" + serviceRequest.Service + "' before authenticating")
 	}
 	serviceAccept := serviceAcceptMsg{
 		Service: serviceUserAuth,
@@ -420,9 +420,9 @@ func (s *ServerConn) testPubKey(user, algo string, pubKey []byte) bool {
 	return result
 }
 
-func (s *ServerConn) authenticate(H []byte) os.Error {
+func (s *ServerConn) authenticate(H []byte) error {
 	var userAuthReq userAuthRequestMsg
-	var err os.Error
+	var err error
 	var packet []byte
 
 userAuthLoop:
@@ -435,7 +435,7 @@ userAuthLoop:
 		}
 
 		if userAuthReq.Service != serviceSSH {
-			return os.NewError("ssh: client attempted to negotiate for unknown service: " + userAuthReq.Service)
+			return errors.New("ssh: client attempted to negotiate for unknown service: " + userAuthReq.Service)
 		}
 
 		switch userAuthReq.Method {
@@ -523,7 +523,7 @@ userAuthLoop:
 						return ParseError{msgUserAuthRequest}
 					}
 				default:
-					return os.NewError("ssh: isAcceptableAlgo incorrect")
+					return errors.New("ssh: isAcceptableAlgo incorrect")
 				}
 				if s.testPubKey(userAuthReq.User, algo, pubKey) {
 					break userAuthLoop
@@ -540,7 +540,7 @@ userAuthLoop:
 		}
 
 		if len(failureMsg.Methods) == 0 {
-			return os.NewError("ssh: no authentication methods configured but NoClientAuth is also false")
+			return errors.New("ssh: no authentication methods configured but NoClientAuth is also false")
 		}
 
 		if err = s.writePacket(marshal(msgUserAuthFailure, failureMsg)); err != nil {
@@ -560,7 +560,7 @@ const defaultWindowSize = 32768
 
 // Accept reads and processes messages on a ServerConn. It must be called
 // in order to demultiplex messages to any resulting Channels.
-func (s *ServerConn) Accept() (Channel, os.Error) {
+func (s *ServerConn) Accept() (Channel, error) {
 	if s.err != nil {
 		return nil, s.err
 	}
@@ -660,7 +660,7 @@ func (s *ServerConn) Accept() (Channel, os.Error) {
 			case UnexpectedMessageError:
 				return nil, msg
 			case *disconnectMsg:
-				return nil, os.EOF
+				return nil, io.EOF
 			default:
 				// Unknown message. Ignore.
 			}
@@ -679,7 +679,7 @@ type Listener struct {
 // Accept waits for and returns the next incoming SSH connection.
 // The receiver should call Handshake() in another goroutine 
 // to avoid blocking the accepter.
-func (l *Listener) Accept() (*ServerConn, os.Error) {
+func (l *Listener) Accept() (*ServerConn, error) {
 	c, err := l.listener.Accept()
 	if err != nil {
 		return nil, err
@@ -694,13 +694,13 @@ func (l *Listener) Addr() net.Addr {
 }
 
 // Close closes the listener.
-func (l *Listener) Close() os.Error {
+func (l *Listener) Close() error {
 	return l.listener.Close()
 }
 
 // Listen creates an SSH listener accepting connections on
 // the given network address using net.Listen.
-func Listen(network, addr string, config *ServerConfig) (*Listener, os.Error) {
+func Listen(network, addr string, config *ServerConfig) (*Listener, error) {
 	l, err := net.Listen(network, addr)
 	if err != nil {
 		return nil, err
diff --git a/src/pkg/exp/ssh/server_shell.go b/src/pkg/exp/ssh/server_shell.go
index 0e9967a909..5243d0ee7f 100644
--- a/src/pkg/exp/ssh/server_shell.go
+++ b/src/pkg/exp/ssh/server_shell.go
@@ -4,9 +4,7 @@
 
 package ssh
 
-import (
-	"os"
-)
+import "io"
 
 // ServerShell contains the state for running a VT100 terminal that is capable
 // of reading lines of input.
@@ -326,12 +324,12 @@ func parsePtyRequest(s []byte) (width, height int, ok bool) {
 	return
 }
 
-func (ss *ServerShell) Write(buf []byte) (n int, err os.Error) {
+func (ss *ServerShell) Write(buf []byte) (n int, err error) {
 	return ss.c.Write(buf)
 }
 
 // ReadLine returns a line of input from the terminal.
-func (ss *ServerShell) ReadLine() (line string, err os.Error) {
+func (ss *ServerShell) ReadLine() (line string, err error) {
 	ss.writeLine([]byte(ss.prompt))
 	ss.c.Write(ss.outBuf)
 	ss.outBuf = ss.outBuf[:0]
@@ -353,7 +351,7 @@ func (ss *ServerShell) ReadLine() (line string, err os.Error) {
 					break
 				}
 				if key == keyCtrlD {
-					return "", os.EOF
+					return "", io.EOF
 				}
 				line, lineOk = ss.handleKey(key)
 			}
diff --git a/src/pkg/exp/ssh/server_shell_test.go b/src/pkg/exp/ssh/server_shell_test.go
index 622cf7cfad..aa69ef7fed 100644
--- a/src/pkg/exp/ssh/server_shell_test.go
+++ b/src/pkg/exp/ssh/server_shell_test.go
@@ -5,8 +5,8 @@
 package ssh
 
 import (
+	"io"
 	"testing"
-	"os"
 )
 
 type MockChannel struct {
@@ -15,15 +15,15 @@ type MockChannel struct {
 	received     []byte
 }
 
-func (c *MockChannel) Accept() os.Error {
+func (c *MockChannel) Accept() error {
 	return nil
 }
 
-func (c *MockChannel) Reject(RejectionReason, string) os.Error {
+func (c *MockChannel) Reject(RejectionReason, string) error {
 	return nil
 }
 
-func (c *MockChannel) Read(data []byte) (n int, err os.Error) {
+func (c *MockChannel) Read(data []byte) (n int, err error) {
 	n = len(data)
 	if n == 0 {
 		return
@@ -32,7 +32,7 @@ func (c *MockChannel) Read(data []byte) (n int, err os.Error) {
 		n = len(c.toSend)
 	}
 	if n == 0 {
-		return 0, os.EOF
+		return 0, io.EOF
 	}
 	if c.bytesPerRead > 0 && n > c.bytesPerRead {
 		n = c.bytesPerRead
@@ -42,16 +42,16 @@ func (c *MockChannel) Read(data []byte) (n int, err os.Error) {
 	return
 }
 
-func (c *MockChannel) Write(data []byte) (n int, err os.Error) {
+func (c *MockChannel) Write(data []byte) (n int, err error) {
 	c.received = append(c.received, data...)
 	return len(data), nil
 }
 
-func (c *MockChannel) Close() os.Error {
+func (c *MockChannel) Close() error {
 	return nil
 }
 
-func (c *MockChannel) AckRequest(ok bool) os.Error {
+func (c *MockChannel) AckRequest(ok bool) error {
 	return nil
 }
 
@@ -70,7 +70,7 @@ func TestClose(t *testing.T) {
 	if line != "" {
 		t.Errorf("Expected empty line but got: %s", line)
 	}
-	if err != os.EOF {
+	if err != io.EOF {
 		t.Errorf("Error should have been EOF but got: %s", err)
 	}
 }
@@ -78,12 +78,12 @@ func TestClose(t *testing.T) {
 var keyPressTests = []struct {
 	in   string
 	line string
-	err  os.Error
+	err  error
 }{
 	{
 		"",
 		"",
-		os.EOF,
+		io.EOF,
 	},
 	{
 		"\r",
diff --git a/src/pkg/exp/ssh/session.go b/src/pkg/exp/ssh/session.go
index 13df2f0dda..77154f2c3c 100644
--- a/src/pkg/exp/ssh/session.go
+++ b/src/pkg/exp/ssh/session.go
@@ -9,8 +9,8 @@ package ssh
 
 import (
 	"encoding/binary"
+	"errors"
 	"io"
-	"os"
 )
 
 // A Session represents a connection to a remote command or shell.
@@ -34,7 +34,7 @@ type Session struct {
 
 // Setenv sets an environment variable that will be applied to any
 // command executed by Shell or Exec.
-func (s *Session) Setenv(name, value string) os.Error {
+func (s *Session) Setenv(name, value string) error {
 	n, v := []byte(name), []byte(value)
 	nlen, vlen := stringLength(n), stringLength(v)
 	payload := make([]byte, nlen+vlen)
@@ -53,7 +53,7 @@ func (s *Session) Setenv(name, value string) os.Error {
 var emptyModeList = []byte{0, 0, 0, 1, 0}
 
 // RequestPty requests the association of a pty with the session on the remote host.
-func (s *Session) RequestPty(term string, h, w int) os.Error {
+func (s *Session) RequestPty(term string, h, w int) error {
 	buf := make([]byte, 4+len(term)+16+len(emptyModeList))
 	b := marshalString(buf, []byte(term))
 	binary.BigEndian.PutUint32(b, uint32(h))
@@ -73,9 +73,9 @@ func (s *Session) RequestPty(term string, h, w int) os.Error {
 // Exec runs cmd on the remote host. Typically, the remote 
 // server passes cmd to the shell for interpretation. 
 // A Session only accepts one call to Exec or Shell.
-func (s *Session) Exec(cmd string) os.Error {
+func (s *Session) Exec(cmd string) error {
 	if s.started {
-		return os.NewError("session already started")
+		return errors.New("session already started")
 	}
 	cmdLen := stringLength([]byte(cmd))
 	payload := make([]byte, cmdLen)
@@ -92,9 +92,9 @@ func (s *Session) Exec(cmd string) os.Error {
 
 // Shell starts a login shell on the remote host. A Session only 
 // accepts one call to Exec or Shell.
-func (s *Session) Shell() os.Error {
+func (s *Session) Shell() error {
 	if s.started {
-		return os.NewError("session already started")
+		return errors.New("session already started")
 	}
 	s.started = true
 
@@ -106,7 +106,7 @@ func (s *Session) Shell() os.Error {
 }
 
 // NewSession returns a new interactive session on the remote host.
-func (c *ClientConn) NewSession() (*Session, os.Error) {
+func (c *ClientConn) NewSession() (*Session, error) {
 	ch, err := c.openChan("session")
 	if err != nil {
 		return nil, err
diff --git a/src/pkg/exp/ssh/transport.go b/src/pkg/exp/ssh/transport.go
index 97eaf975d1..579a9d82de 100644
--- a/src/pkg/exp/ssh/transport.go
+++ b/src/pkg/exp/ssh/transport.go
@@ -11,10 +11,10 @@ import (
 	"crypto/cipher"
 	"crypto/hmac"
 	"crypto/subtle"
+	"errors"
 	"hash"
 	"io"
 	"net"
-	"os"
 	"sync"
 )
 
@@ -27,7 +27,7 @@ const (
 // TODO(dfc) suggestions for a better name will be warmly received.
 type filteredConn interface {
 	// Close closes the connection.
-	Close() os.Error
+	Close() error
 
 	// LocalAddr returns the local network address.
 	LocalAddr() net.Addr
@@ -40,7 +40,7 @@ type filteredConn interface {
 // an SSH peer.
 type packetWriter interface {
 	// Encrypt and send a packet of data to the remote peer.
-	writePacket(packet []byte) os.Error
+	writePacket(packet []byte) error
 }
 
 // transport represents the SSH connection to the remote peer.
@@ -79,7 +79,7 @@ type common struct {
 }
 
 // Read and decrypt a single packet from the remote peer.
-func (r *reader) readOnePacket() ([]byte, os.Error) {
+func (r *reader) readOnePacket() ([]byte, error) {
 	var lengthBytes = make([]byte, 5)
 	var macSize uint32
 
@@ -108,10 +108,10 @@ func (r *reader) readOnePacket() ([]byte, os.Error) {
 	paddingLength := uint32(lengthBytes[4])
 
 	if length <= paddingLength+1 {
-		return nil, os.NewError("invalid packet length")
+		return nil, errors.New("invalid packet length")
 	}
 	if length > maxPacketSize {
-		return nil, os.NewError("packet too large")
+		return nil, errors.New("packet too large")
 	}
 
 	packet := make([]byte, length-1+macSize)
@@ -126,7 +126,7 @@ func (r *reader) readOnePacket() ([]byte, os.Error) {
 	if r.mac != nil {
 		r.mac.Write(packet[:length-1])
 		if subtle.ConstantTimeCompare(r.mac.Sum(), mac) != 1 {
-			return nil, os.NewError("ssh: MAC failure")
+			return nil, errors.New("ssh: MAC failure")
 		}
 	}
 
@@ -135,7 +135,7 @@ func (r *reader) readOnePacket() ([]byte, os.Error) {
 }
 
 // Read and decrypt next packet discarding debug and noop messages.
-func (t *transport) readPacket() ([]byte, os.Error) {
+func (t *transport) readPacket() ([]byte, error) {
 	for {
 		packet, err := t.readOnePacket()
 		if err != nil {
@@ -149,7 +149,7 @@ func (t *transport) readPacket() ([]byte, os.Error) {
 }
 
 // Encrypt and send a packet of data to the remote peer.
-func (w *writer) writePacket(packet []byte) os.Error {
+func (w *writer) writePacket(packet []byte) error {
 	w.Mutex.Lock()
 	defer w.Mutex.Unlock()
 
@@ -218,7 +218,7 @@ func (w *writer) writePacket(packet []byte) os.Error {
 }
 
 // Send a message to the remote peer
-func (t *transport) sendMessage(typ uint8, msg interface{}) os.Error {
+func (t *transport) sendMessage(typ uint8, msg interface{}) error {
 	packet := marshal(typ, msg)
 	return t.writePacket(packet)
 }
@@ -252,7 +252,7 @@ var (
 // setupKeys sets the cipher and MAC keys from K, H and sessionId, as
 // described in RFC 4253, section 6.4. direction should either be serverKeys
 // (to setup server->client keys) or clientKeys (for client->server keys).
-func (c *common) setupKeys(d direction, K, H, sessionId []byte, hashFunc crypto.Hash) os.Error {
+func (c *common) setupKeys(d direction, K, H, sessionId []byte, hashFunc crypto.Hash) error {
 	h := hashFunc.New()
 
 	blockSize := 16
@@ -308,7 +308,7 @@ type truncatingMAC struct {
 	hmac   hash.Hash
 }
 
-func (t truncatingMAC) Write(data []byte) (int, os.Error) {
+func (t truncatingMAC) Write(data []byte) (int, error) {
 	return t.hmac.Write(data)
 }
 
@@ -332,7 +332,7 @@ func (t truncatingMAC) Size() int {
 const maxVersionStringBytes = 1024
 
 // Read version string as specified by RFC 4253, section 4.2.
-func readVersion(r io.Reader) ([]byte, os.Error) {
+func readVersion(r io.Reader) ([]byte, error) {
 	versionString := make([]byte, 0, 64)
 	var ok, seenCR bool
 	var buf [1]byte
@@ -360,7 +360,7 @@ forEachByte:
 	}
 
 	if !ok {
-		return nil, os.NewError("failed to read version string")
+		return nil, errors.New("failed to read version string")
 	}
 
 	// We need to remove the CR from versionString
diff --git a/src/pkg/exp/template/html/error.go b/src/pkg/exp/template/html/error.go
index 5515bfe68d..22fca9e060 100644
--- a/src/pkg/exp/template/html/error.go
+++ b/src/pkg/exp/template/html/error.go
@@ -197,7 +197,7 @@ const (
 	ErrSlashAmbig
 )
 
-func (e *Error) String() string {
+func (e *Error) Error() string {
 	if e.Line != 0 {
 		return fmt.Sprintf("exp/template/html:%s:%d: %s", e.Name, e.Line, e.Description)
 	} else if e.Name != "" {
diff --git a/src/pkg/exp/template/html/escape.go b/src/pkg/exp/template/html/escape.go
index 74abccecdd..28615a9318 100644
--- a/src/pkg/exp/template/html/escape.go
+++ b/src/pkg/exp/template/html/escape.go
@@ -8,14 +8,13 @@ import (
 	"bytes"
 	"fmt"
 	"html"
-	"os"
 	"template"
 	"template/parse"
 )
 
 // Escape rewrites each action in the template to guarantee that the output is
 // properly escaped.
-func Escape(t *template.Template) (*template.Template, os.Error) {
+func Escape(t *template.Template) (*template.Template, error) {
 	var s template.Set
 	s.Add(t)
 	if _, err := EscapeSet(&s, t.Name()); err != nil {
@@ -32,7 +31,7 @@ func Escape(t *template.Template) (*template.Template, os.Error) {
 // need not include helper templates.
 // If no error is returned, then the named templates have been modified. 
 // Otherwise the named templates have been rendered unusable.
-func EscapeSet(s *template.Set, names ...string) (*template.Set, os.Error) {
+func EscapeSet(s *template.Set, names ...string) (*template.Set, error) {
 	if len(names) == 0 {
 		// TODO: Maybe add a method to Set to enumerate template names
 		// and use those instead.
@@ -41,7 +40,7 @@ func EscapeSet(s *template.Set, names ...string) (*template.Set, os.Error) {
 	e := newEscaper(s)
 	for _, name := range names {
 		c, _ := e.escapeTree(context{}, name, 0)
-		var err os.Error
+		var err error
 		if c.err != nil {
 			err, c.err.Name = c.err, name
 		} else if c.state != stateText {
diff --git a/src/pkg/exp/template/html/escape_test.go b/src/pkg/exp/template/html/escape_test.go
index 1b3b256733..20599bce15 100644
--- a/src/pkg/exp/template/html/escape_test.go
+++ b/src/pkg/exp/template/html/escape_test.go
@@ -8,7 +8,6 @@ import (
 	"bytes"
 	"fmt"
 	"json"
-	"os"
 	"strings"
 	"template"
 	"template/parse"
@@ -17,14 +16,14 @@ import (
 
 type badMarshaler struct{}
 
-func (x *badMarshaler) MarshalJSON() ([]byte, os.Error) {
+func (x *badMarshaler) MarshalJSON() ([]byte, error) {
 	// Keys in valid JSON must be double quoted as must all strings.
 	return []byte("{ foo: 'not quite valid JSON' }"), nil
 }
 
 type goodMarshaler struct{}
 
-func (x *goodMarshaler) MarshalJSON() ([]byte, os.Error) {
+func (x *goodMarshaler) MarshalJSON() ([]byte, error) {
 	return []byte(`{ "<foo>": "O'Reilly" }`), nil
 }
 
@@ -783,7 +782,7 @@ func TestEscapeSet(t *testing.T) {
 
 	// pred is a template function that returns the predecessor of a
 	// natural number for testing recursive templates.
-	fns := template.FuncMap{"pred": func(a ...interface{}) (interface{}, os.Error) {
+	fns := template.FuncMap{"pred": func(a ...interface{}) (interface{}, error) {
 		if len(a) == 1 {
 			if i, _ := a[0].(int); i > 0 {
 				return i - 1, nil
@@ -807,7 +806,7 @@ func TestEscapeSet(t *testing.T) {
 		var b bytes.Buffer
 
 		if err := s.Execute(&b, "main", data); err != nil {
-			t.Errorf("%q executing %v", err.String(), s.Template("main"))
+			t.Errorf("%q executing %v", err.Error(), s.Template("main"))
 			continue
 		}
 		if got := b.String(); test.want != got {
@@ -962,7 +961,7 @@ func TestErrors(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		var err os.Error
+		var err error
 		if strings.HasPrefix(test.input, "{{define") {
 			var s template.Set
 			_, err = s.Parse(test.input)
@@ -977,7 +976,7 @@ func TestErrors(t *testing.T) {
 		}
 		var got string
 		if err != nil {
-			got = err.String()
+			got = err.Error()
 		}
 		if test.err == "" {
 			if got != "" {
@@ -1549,7 +1548,7 @@ func TestEnsurePipelineContains(t *testing.T) {
 	}
 }
 
-func expectExecuteFailure(t *testing.T, b *bytes.Buffer, err os.Error) {
+func expectExecuteFailure(t *testing.T, b *bytes.Buffer, err error) {
 	if err != nil {
 		if b.Len() != 0 {
 			t.Errorf("output on buffer: %q", b.String())
diff --git a/src/pkg/exp/template/html/js.go b/src/pkg/exp/template/html/js.go
index 5646f8a4fd..22be4183d7 100644
--- a/src/pkg/exp/template/html/js.go
+++ b/src/pkg/exp/template/html/js.go
@@ -148,7 +148,7 @@ func jsValEscaper(args ...interface{}) string {
 		// turning into
 		//     x//* error marshalling y:
 		//          second line of error message */null
-		return fmt.Sprintf(" /* %s */null ", strings.Replace(err.String(), "*/", "* /", -1))
+		return fmt.Sprintf(" /* %s */null ", strings.Replace(err.Error(), "*/", "* /", -1))
 	}
 
 	// TODO: maybe post-process output to prevent it from containing
diff --git a/src/pkg/exp/terminal/shell.go b/src/pkg/exp/terminal/shell.go
index e3f584774e..5c5916755d 100644
--- a/src/pkg/exp/terminal/shell.go
+++ b/src/pkg/exp/terminal/shell.go
@@ -4,10 +4,7 @@
 
 package terminal
 
-import (
-	"os"
-	"io"
-)
+import "io"
 
 // Shell contains the state for running a VT100 terminal that is capable of
 // reading lines of input.
@@ -306,12 +303,12 @@ func (ss *Shell) writeLine(line []byte) {
 	}
 }
 
-func (ss *Shell) Write(buf []byte) (n int, err os.Error) {
+func (ss *Shell) Write(buf []byte) (n int, err error) {
 	return ss.c.Write(buf)
 }
 
 // ReadLine returns a line of input from the terminal.
-func (ss *Shell) ReadLine() (line string, err os.Error) {
+func (ss *Shell) ReadLine() (line string, err error) {
 	ss.writeLine([]byte(ss.prompt))
 	ss.c.Write(ss.outBuf)
 	ss.outBuf = ss.outBuf[:0]
@@ -337,7 +334,7 @@ func (ss *Shell) ReadLine() (line string, err os.Error) {
 					break
 				}
 				if key == keyCtrlD {
-					return "", os.EOF
+					return "", io.EOF
 				}
 				line, lineOk = ss.handleKey(key)
 			}
diff --git a/src/pkg/exp/terminal/shell_test.go b/src/pkg/exp/terminal/shell_test.go
index 2bbe4a4f8f..8a76a85d5d 100644
--- a/src/pkg/exp/terminal/shell_test.go
+++ b/src/pkg/exp/terminal/shell_test.go
@@ -5,8 +5,8 @@
 package terminal
 
 import (
+	"io"
 	"testing"
-	"os"
 )
 
 type MockTerminal struct {
@@ -15,7 +15,7 @@ type MockTerminal struct {
 	received     []byte
 }
 
-func (c *MockTerminal) Read(data []byte) (n int, err os.Error) {
+func (c *MockTerminal) Read(data []byte) (n int, err error) {
 	n = len(data)
 	if n == 0 {
 		return
@@ -24,7 +24,7 @@ func (c *MockTerminal) Read(data []byte) (n int, err os.Error) {
 		n = len(c.toSend)
 	}
 	if n == 0 {
-		return 0, os.EOF
+		return 0, io.EOF
 	}
 	if c.bytesPerRead > 0 && n > c.bytesPerRead {
 		n = c.bytesPerRead
@@ -34,7 +34,7 @@ func (c *MockTerminal) Read(data []byte) (n int, err os.Error) {
 	return
 }
 
-func (c *MockTerminal) Write(data []byte) (n int, err os.Error) {
+func (c *MockTerminal) Write(data []byte) (n int, err error) {
 	c.received = append(c.received, data...)
 	return len(data), nil
 }
@@ -46,7 +46,7 @@ func TestClose(t *testing.T) {
 	if line != "" {
 		t.Errorf("Expected empty line but got: %s", line)
 	}
-	if err != os.EOF {
+	if err != io.EOF {
 		t.Errorf("Error should have been EOF but got: %s", err)
 	}
 }
@@ -54,12 +54,12 @@ func TestClose(t *testing.T) {
 var keyPressTests = []struct {
 	in   string
 	line string
-	err  os.Error
+	err  error
 }{
 	{
 		"",
 		"",
-		os.EOF,
+		io.EOF,
 	},
 	{
 		"\r",
diff --git a/src/pkg/exp/terminal/terminal.go b/src/pkg/exp/terminal/terminal.go
index aacd90905f..d711493819 100644
--- a/src/pkg/exp/terminal/terminal.go
+++ b/src/pkg/exp/terminal/terminal.go
@@ -15,6 +15,7 @@
 package terminal
 
 import (
+	"io"
 	"os"
 	"syscall"
 	"unsafe"
@@ -35,7 +36,7 @@ func IsTerminal(fd int) bool {
 // MakeRaw put the terminal connected to the given file descriptor into raw
 // mode and returns the previous state of the terminal so that it can be
 // restored.
-func MakeRaw(fd int) (*State, os.Error) {
+func MakeRaw(fd int) (*State, error) {
 	var oldState State
 	if _, _, e := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall.TCGETS), uintptr(unsafe.Pointer(&oldState.termios)), 0, 0, 0); e != 0 {
 		return nil, os.Errno(e)
@@ -53,7 +54,7 @@ func MakeRaw(fd int) (*State, os.Error) {
 
 // Restore restores the terminal connected to the given file descriptor to a
 // previous state.
-func Restore(fd int, state *State) os.Error {
+func Restore(fd int, state *State) error {
 	_, _, e := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall.TCSETS), uintptr(unsafe.Pointer(&state.termios)), 0, 0, 0)
 	return os.Errno(e)
 }
@@ -61,7 +62,7 @@ func Restore(fd int, state *State) os.Error {
 // ReadPassword reads a line of input from a terminal without local echo.  This
 // is commonly used for inputting passwords and other sensitive data. The slice
 // returned does not include the \n.
-func ReadPassword(fd int) ([]byte, os.Error) {
+func ReadPassword(fd int) ([]byte, error) {
 	var oldState syscall.Termios
 	if _, _, e := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall.TCGETS), uintptr(unsafe.Pointer(&oldState)), 0, 0, 0); e != 0 {
 		return nil, os.Errno(e)
@@ -86,7 +87,7 @@ func ReadPassword(fd int) ([]byte, os.Error) {
 		}
 		if n == 0 {
 			if len(ret) == 0 {
-				return nil, os.EOF
+				return nil, io.EOF
 			}
 			break
 		}
diff --git a/src/pkg/exp/types/check.go b/src/pkg/exp/types/check.go
index 87e3e93da7..09e29d1261 100644
--- a/src/pkg/exp/types/check.go
+++ b/src/pkg/exp/types/check.go
@@ -11,7 +11,6 @@ import (
 	"go/ast"
 	"go/scanner"
 	"go/token"
-	"os"
 	"strconv"
 )
 
@@ -213,7 +212,7 @@ func (c *checker) checkObj(obj *ast.Object, ref bool) {
 // of types for all expression nodes in statements, and a scanner.ErrorList if
 // there are errors.
 //
-func Check(fset *token.FileSet, pkg *ast.Package) (types map[ast.Expr]Type, err os.Error) {
+func Check(fset *token.FileSet, pkg *ast.Package) (types map[ast.Expr]Type, err error) {
 	var c checker
 	c.fset = fset
 	c.types = make(map[ast.Expr]Type)
diff --git a/src/pkg/exp/types/check_test.go b/src/pkg/exp/types/check_test.go
index 034acd00de..4a30acf231 100644
--- a/src/pkg/exp/types/check_test.go
+++ b/src/pkg/exp/types/check_test.go
@@ -67,7 +67,7 @@ func getPos(filename string, offset int) token.Pos {
 
 // TODO(gri) Need to revisit parser interface. We should be able to use parser.ParseFiles
 //           or a similar function instead.
-func parseFiles(t *testing.T, testname string, filenames []string) (map[string]*ast.File, os.Error) {
+func parseFiles(t *testing.T, testname string, filenames []string) (map[string]*ast.File, error) {
 	files := make(map[string]*ast.File)
 	var errors scanner.ErrorList
 	for _, filename := range filenames {
@@ -132,7 +132,7 @@ func expectedErrors(t *testing.T, testname string, files map[string]*ast.File) m
 	return errors
 }
 
-func eliminate(t *testing.T, expected map[token.Pos]string, errors os.Error) {
+func eliminate(t *testing.T, expected map[token.Pos]string, errors error) {
 	if errors == nil {
 		return
 	}
diff --git a/src/pkg/exp/types/exportdata.go b/src/pkg/exp/types/exportdata.go
index 784ffff01a..fa5b6a37fe 100644
--- a/src/pkg/exp/types/exportdata.go
+++ b/src/pkg/exp/types/exportdata.go
@@ -8,6 +8,7 @@ package types
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -15,7 +16,7 @@ import (
 	"strings"
 )
 
-func readGopackHeader(buf *bufio.Reader) (name string, size int, err os.Error) {
+func readGopackHeader(buf *bufio.Reader) (name string, size int, err error) {
 	// See $GOROOT/include/ar.h.
 	hdr := make([]byte, 16+12+6+6+8+10+2)
 	_, err = io.ReadFull(buf, hdr)
@@ -28,7 +29,7 @@ func readGopackHeader(buf *bufio.Reader) (name string, size int, err os.Error) {
 	s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10]))
 	size, err = strconv.Atoi(s)
 	if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
-		err = os.NewError("invalid archive header")
+		err = errors.New("invalid archive header")
 		return
 	}
 	name = strings.TrimSpace(string(hdr[:16]))
@@ -44,7 +45,7 @@ type dataReader struct {
 // export data section of the given object/archive file, or an error.
 // It is the caller's responsibility to close the readCloser.
 //
-func ExportData(filename string) (rc io.ReadCloser, err os.Error) {
+func ExportData(filename string) (rc io.ReadCloser, err error) {
 	file, err := os.Open(filename)
 	if err != nil {
 		return
@@ -77,7 +78,7 @@ func ExportData(filename string) (rc io.ReadCloser, err os.Error) {
 			return
 		}
 		if name != "__.SYMDEF" {
-			err = os.NewError("go archive does not begin with __.SYMDEF")
+			err = errors.New("go archive does not begin with __.SYMDEF")
 			return
 		}
 		const block = 4096
@@ -99,7 +100,7 @@ func ExportData(filename string) (rc io.ReadCloser, err os.Error) {
 			return
 		}
 		if name != "__.PKGDEF" {
-			err = os.NewError("go archive is missing __.PKGDEF")
+			err = errors.New("go archive is missing __.PKGDEF")
 			return
 		}
 
@@ -114,7 +115,7 @@ func ExportData(filename string) (rc io.ReadCloser, err os.Error) {
 	// Now at __.PKGDEF in archive or still at beginning of file.
 	// Either way, line should begin with "go object ".
 	if !strings.HasPrefix(string(line), "go object ") {
-		err = os.NewError("not a go object file")
+		err = errors.New("not a go object file")
 		return
 	}
 
diff --git a/src/pkg/exp/types/gcimporter.go b/src/pkg/exp/types/gcimporter.go
index 4e5172a3d2..d88af95031 100644
--- a/src/pkg/exp/types/gcimporter.go
+++ b/src/pkg/exp/types/gcimporter.go
@@ -9,6 +9,7 @@ package types
 
 import (
 	"big"
+	"errors"
 	"fmt"
 	"go/ast"
 	"go/token"
@@ -102,7 +103,7 @@ func (p *gcParser) next() {
 }
 
 // GcImporter implements the ast.Importer signature.
-func GcImporter(imports map[string]*ast.Object, path string) (pkg *ast.Object, err os.Error) {
+func GcImporter(imports map[string]*ast.Object, path string) (pkg *ast.Object, err error) {
 	if path == "unsafe" {
 		return Unsafe, nil
 	}
@@ -118,7 +119,7 @@ func GcImporter(imports map[string]*ast.Object, path string) (pkg *ast.Object, e
 
 	filename, id := findPkg(path)
 	if filename == "" {
-		err = os.NewError("can't find import: " + id)
+		err = errors.New("can't find import: " + id)
 		return
 	}
 
@@ -176,19 +177,19 @@ func (p *gcParser) declare(scope *ast.Scope, kind ast.ObjKind, name string) *ast
 // Internal errors are boxed as importErrors.
 type importError struct {
 	pos scanner.Position
-	err os.Error
+	err error
 }
 
-func (e importError) String() string {
+func (e importError) Error() string {
 	return fmt.Sprintf("import error %s (byte offset = %d): %s", e.pos, e.pos.Offset, e.err)
 }
 
 func (p *gcParser) error(err interface{}) {
 	if s, ok := err.(string); ok {
-		err = os.NewError(s)
+		err = errors.New(s)
 	}
 	// panic with a runtime.Error if err is not an os.Error
-	panic(importError{p.scanner.Pos(), err.(os.Error)})
+	panic(importError{p.scanner.Pos(), err.(error)})
 }
 
 func (p *gcParser) errorf(format string, args ...interface{}) {
diff --git a/src/pkg/exp/winfsnotify/winfsnotify.go b/src/pkg/exp/winfsnotify/winfsnotify.go
index c5dfe99ad7..d133740304 100644
--- a/src/pkg/exp/winfsnotify/winfsnotify.go
+++ b/src/pkg/exp/winfsnotify/winfsnotify.go
@@ -7,6 +7,7 @@
 package winfsnotify
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -36,7 +37,7 @@ type input struct {
 	op    int
 	path  string
 	flags uint32
-	reply chan os.Error
+	reply chan error
 }
 
 type inode struct {
@@ -65,14 +66,14 @@ type Watcher struct {
 	watches  watchMap       // Map of watches (key: i-number)
 	input    chan *input    // Inputs to the reader are sent on this channel
 	Event    chan *Event    // Events are returned on this channel
-	Error    chan os.Error  // Errors are sent on this channel
+	Error    chan error     // Errors are sent on this channel
 	isClosed bool           // Set to true when Close() is first called
-	quit     chan chan<- os.Error
+	quit     chan chan<- error
 	cookie   uint32
 }
 
 // NewWatcher creates and returns a Watcher.
-func NewWatcher() (*Watcher, os.Error) {
+func NewWatcher() (*Watcher, error) {
 	port, e := syscall.CreateIoCompletionPort(syscall.InvalidHandle, 0, 0, 0)
 	if e != 0 {
 		return nil, os.NewSyscallError("CreateIoCompletionPort", e)
@@ -82,8 +83,8 @@ func NewWatcher() (*Watcher, os.Error) {
 		watches: make(watchMap),
 		input:   make(chan *input, 1),
 		Event:   make(chan *Event, 50),
-		Error:   make(chan os.Error),
-		quit:    make(chan chan<- os.Error, 1),
+		Error:   make(chan error),
+		quit:    make(chan chan<- error, 1),
 	}
 	go w.readEvents()
 	return w, nil
@@ -92,14 +93,14 @@ func NewWatcher() (*Watcher, os.Error) {
 // Close closes a Watcher.
 // It sends a message to the reader goroutine to quit and removes all watches
 // associated with the watcher.
-func (w *Watcher) Close() os.Error {
+func (w *Watcher) Close() error {
 	if w.isClosed {
 		return nil
 	}
 	w.isClosed = true
 
 	// Send "quit" message to the reader goroutine
-	ch := make(chan os.Error)
+	ch := make(chan error)
 	w.quit <- ch
 	if err := w.wakeupReader(); err != nil {
 		return err
@@ -108,15 +109,15 @@ func (w *Watcher) Close() os.Error {
 }
 
 // AddWatch adds path to the watched file set.
-func (w *Watcher) AddWatch(path string, flags uint32) os.Error {
+func (w *Watcher) AddWatch(path string, flags uint32) error {
 	if w.isClosed {
-		return os.NewError("watcher already closed")
+		return errors.New("watcher already closed")
 	}
 	in := &input{
 		op:    opAddWatch,
 		path:  filepath.Clean(path),
 		flags: flags,
-		reply: make(chan os.Error),
+		reply: make(chan error),
 	}
 	w.input <- in
 	if err := w.wakeupReader(); err != nil {
@@ -126,16 +127,16 @@ func (w *Watcher) AddWatch(path string, flags uint32) os.Error {
 }
 
 // Watch adds path to the watched file set, watching all events.
-func (w *Watcher) Watch(path string) os.Error {
+func (w *Watcher) Watch(path string) error {
 	return w.AddWatch(path, FS_ALL_EVENTS)
 }
 
 // RemoveWatch removes path from the watched file set.
-func (w *Watcher) RemoveWatch(path string) os.Error {
+func (w *Watcher) RemoveWatch(path string) error {
 	in := &input{
 		op:    opRemoveWatch,
 		path:  filepath.Clean(path),
-		reply: make(chan os.Error),
+		reply: make(chan error),
 	}
 	w.input <- in
 	if err := w.wakeupReader(); err != nil {
@@ -144,7 +145,7 @@ func (w *Watcher) RemoveWatch(path string) os.Error {
 	return <-in.reply
 }
 
-func (w *Watcher) wakeupReader() os.Error {
+func (w *Watcher) wakeupReader() error {
 	e := syscall.PostQueuedCompletionStatus(w.port, 0, 0, nil)
 	if e != 0 {
 		return os.NewSyscallError("PostQueuedCompletionStatus", e)
@@ -152,7 +153,7 @@ func (w *Watcher) wakeupReader() os.Error {
 	return nil
 }
 
-func getDir(pathname string) (dir string, err os.Error) {
+func getDir(pathname string) (dir string, err error) {
 	attr, e := syscall.GetFileAttributes(syscall.StringToUTF16Ptr(pathname))
 	if e != 0 {
 		return "", os.NewSyscallError("GetFileAttributes", e)
@@ -166,7 +167,7 @@ func getDir(pathname string) (dir string, err os.Error) {
 	return
 }
 
-func getIno(path string) (ino *inode, err os.Error) {
+func getIno(path string) (ino *inode, err error) {
 	h, e := syscall.CreateFile(syscall.StringToUTF16Ptr(path),
 		syscall.FILE_LIST_DIRECTORY,
 		syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE|syscall.FILE_SHARE_DELETE,
@@ -207,7 +208,7 @@ func (m watchMap) set(ino *inode, watch *watch) {
 }
 
 // Must run within the I/O thread.
-func (w *Watcher) addWatch(pathname string, flags uint64) os.Error {
+func (w *Watcher) addWatch(pathname string, flags uint64) error {
 	dir, err := getDir(pathname)
 	if err != nil {
 		return err
@@ -252,7 +253,7 @@ func (w *Watcher) addWatch(pathname string, flags uint64) os.Error {
 }
 
 // Must run within the I/O thread.
-func (w *Watcher) removeWatch(pathname string) os.Error {
+func (w *Watcher) removeWatch(pathname string) error {
 	dir, err := getDir(pathname)
 	if err != nil {
 		return err
@@ -293,7 +294,7 @@ func (w *Watcher) deleteWatch(watch *watch) {
 }
 
 // Must run within the I/O thread.
-func (w *Watcher) startRead(watch *watch) os.Error {
+func (w *Watcher) startRead(watch *watch) error {
 	if e := syscall.CancelIo(watch.ino.handle); e != 0 {
 		w.Error <- os.NewSyscallError("CancelIo", e)
 		w.deleteWatch(watch)
@@ -352,7 +353,7 @@ func (w *Watcher) readEvents() {
 						w.startRead(watch)
 					}
 				}
-				var err os.Error
+				var err error
 				if e := syscall.CloseHandle(w.port); e != 0 {
 					err = os.NewSyscallError("CloseHandle", e)
 				}
@@ -392,7 +393,7 @@ func (w *Watcher) readEvents() {
 		for {
 			if n == 0 {
 				w.Event <- &Event{Mask: FS_Q_OVERFLOW}
-				w.Error <- os.NewError("short read in readEvents()")
+				w.Error <- errors.New("short read in readEvents()")
 				break
 			}