cmd/gofmt, bufio, image: Consistency and error handling.

cmd/gofmt: Add error handling for ioutil.WriteFile.
bufio: Consistency, rename e to err.
image: Consistency, fix comment for asReader.

R=golang-dev, dave, minux.ma, adg
CC=golang-dev
https://golang.org/cl/7029056

src/cmd/gofmt/gofmt_test.go

@@ -62,7 +62,9 @@ func runTest(t *testing.T, in, out, flags string) {
 		if err == nil {
 			t.Errorf("%s", d)
 		}
-		ioutil.WriteFile(in+".gofmt", got, 0666)
+		if err := ioutil.WriteFile(in+".gofmt", got, 0666); err != nil {
+			t.Error(err)
+		}
 	}
 }
 

src/pkg/bufio/bufio.go

@@ -76,13 +76,13 @@ func (b *Reader) fill() {
 	}
 
 	// Read new data.
-	n, e := b.rd.Read(b.buf[b.w:])
+	n, err := b.rd.Read(b.buf[b.w:])
 	if n < 0 {
 		panic(errNegativeRead)
 	}
 	b.w += n
-	if e != nil {
-		b.err = e
+	if err != nil {
+		b.err = err
 	}
 }
 
@@ -379,8 +379,8 @@ func (b *Reader) ReadBytes(delim byte) (line []byte, err error) {
 // ReadString returns err != nil if and only if the returned data does not end in
 // delim.
 func (b *Reader) ReadString(delim byte) (line string, err error) {
-	bytes, e := b.ReadBytes(delim)
-	return string(bytes), e
+	bytes, err := b.ReadBytes(delim)
+	return string(bytes), err
 }
 
 // WriteTo implements io.WriterTo.
@@ -461,17 +461,17 @@ func (b *Writer) Flush() error {
 	if b.n == 0 {
 		return nil
 	}
-	n, e := b.wr.Write(b.buf[0:b.n])
-	if n < b.n && e == nil {
-		e = io.ErrShortWrite
+	n, err := b.wr.Write(b.buf[0:b.n])
+	if n < b.n && err == nil {
+		err = io.ErrShortWrite
 	}
-	if e != nil {
+	if err != nil {
 		if n > 0 && n < b.n {
 			copy(b.buf[0:b.n-n], b.buf[n:b.n])
 		}
 		b.n -= n
-		b.err = e
-		return e
+		b.err = err
+		return err
 	}
 	b.n = 0
 	return nil

src/pkg/bufio/bufio_test.go

@@ -28,9 +28,9 @@ func newRot13Reader(r io.Reader) *rot13Reader {
 }
 
 func (r13 *rot13Reader) Read(p []byte) (int, error) {
-	n, e := r13.r.Read(p)
-	if e != nil {
-		return n, e
+	n, err := r13.r.Read(p)
+	if err != nil {
+		return n, err
 	}
 	for i := 0; i < n; i++ {
 		c := p[i] | 0x20 // lowercase byte
@@ -48,15 +48,15 @@ func readBytes(buf *Reader) string {
 	var b [1000]byte
 	nb := 0
 	for {
-		c, e := buf.ReadByte()
-		if e == io.EOF {
+		c, err := buf.ReadByte()
+		if err == io.EOF {
 			break
 		}
-		if e == nil {
+		if err == nil {
 			b[nb] = c
 			nb++
-		} else if e != iotest.ErrTimeout {
-			panic("Data: " + e.Error())
+		} else if err != iotest.ErrTimeout {
+			panic("Data: " + err.Error())
 		}
 	}
 	return string(b[0:nb])
@@ -93,12 +93,12 @@ var readMakers = []readMaker{
 func readLines(b *Reader) string {
 	s := ""
 	for {
-		s1, e := b.ReadString('\n')
-		if e == io.EOF {
+		s1, err := b.ReadString('\n')
+		if err == io.EOF {
 			break
 		}
-		if e != nil && e != iotest.ErrTimeout {
-			panic("GetLines: " + e.Error())
+		if err != nil && err != iotest.ErrTimeout {
+			panic("GetLines: " + err.Error())
 		}
 		s += s1
 	}
@@ -110,9 +110,9 @@ func reads(buf *Reader, m int) string {
 	var b [1000]byte
 	nb := 0
 	for {
-		n, e := buf.Read(b[nb : nb+m])
+		n, err := buf.Read(b[nb : nb+m])
 		nb += n
-		if e == io.EOF {
+		if err == io.EOF {
 			break
 		}
 	}

src/pkg/image/format.go

@@ -39,7 +39,7 @@ type reader interface {
 	Peek(int) ([]byte, error)
 }
 
-// AsReader converts an io.Reader to a reader.
+// asReader converts an io.Reader to a reader.
 func asReader(r io.Reader) reader {
 	if rr, ok := r.(reader); ok {
 		return rr