flate: delete WrongValueError type.

Fixes #2838.

R=rsc, r
CC=golang-dev
https://golang.org/cl/5651060

doc/go1.html

@@ -881,10 +881,15 @@ What little code is affected will be caught by the compiler and must be updated
 <h3 id="bufio">The compress/flate, compress/gzip and compress/zlib packages</h3>
 
 <p>
-In Go 1, the NewWriterXxx functions in compress/flate, compress/gzip and
-compress/zlib all return (*Writer, error) if they take a compression level,
-and *Writer otherwise. Package gzip's Compressor and Decompressor types have
-been renamed to Writer and Reader.
+In Go 1, the <code>NewWriterXxx</code> functions in
+<a href="/pkg/compress/flate"><code>compress/flate</code></a>,
+<a href="/pkg/compress/gzip"><code>compress/gzip</code></a> and
+<a href="/pkg/compress/zlib"><code>compress/zlib</code></a>
+all return <code>(*Writer, error)</code> if they take a compression level,
+and <code>*Writer</code> otherwise. Package <code>gzip</code>'s
+<code>Compressor</code> and <code>Decompressor</code> types have been renamed
+to <code>Writer</code> and <code>Reader</code>. Package <code>flate</code>'s
+<code>WrongValueError</code> type has been removed.
 </p>
 
 <p>

doc/go1.tmpl

@@ -785,10 +785,15 @@ What little code is affected will be caught by the compiler and must be updated
 <h3 id="bufio">The compress/flate, compress/gzip and compress/zlib packages</h3>
 
 <p>
-In Go 1, the NewWriterXxx functions in compress/flate, compress/gzip and
-compress/zlib all return (*Writer, error) if they take a compression level,
-and *Writer otherwise. Package gzip's Compressor and Decompressor types have
-been renamed to Writer and Reader.
+In Go 1, the <code>NewWriterXxx</code> functions in
+<a href="/pkg/compress/flate"><code>compress/flate</code></a>,
+<a href="/pkg/compress/gzip"><code>compress/gzip</code></a> and
+<a href="/pkg/compress/zlib"><code>compress/zlib</code></a>
+all return <code>(*Writer, error)</code> if they take a compression level,
+and <code>*Writer</code> otherwise. Package <code>gzip</code>'s
+<code>Compressor</code> and <code>Decompressor</code> types have been renamed
+to <code>Writer</code> and <code>Reader</code>. Package <code>flate</code>'s
+<code>WrongValueError</code> type has been removed.
 </p>
 
 <p>

src/pkg/compress/flate/deflate.go

@@ -5,6 +5,7 @@
 package flate
 
 import (
+	"fmt"
 	"io"
 	"math"
 )
@@ -390,7 +391,7 @@ func (d *compressor) init(w io.Writer, level int) (err error) {
 		d.fill = (*compressor).fillDeflate
 		d.step = (*compressor).deflate
 	default:
-		return WrongValueError{"level", 0, 9, int32(level)}
+		return fmt.Errorf("flate: invalid compression level %d: want value in range [-1, 9]", level)
 	}
 	return nil
 }

src/pkg/compress/flate/huffman_bit_writer.go

@@ -7,7 +7,6 @@ package flate
 import (
 	"io"
 	"math"
-	"strconv"
 )
 
 const (
@@ -85,13 +84,6 @@ type huffmanBitWriter struct {
 	err             error
 }
 
-type WrongValueError struct {
-	name  string
-	from  int32
-	to    int32
-	value int32
-}
-
 func newHuffmanBitWriter(w io.Writer) *huffmanBitWriter {
 	return &huffmanBitWriter{
 		w:               w,
@@ -105,11 +97,6 @@ func newHuffmanBitWriter(w io.Writer) *huffmanBitWriter {
 	}
 }
 
-func (err WrongValueError) Error() string {
-	return "huffmanBitWriter: " + err.name + " should belong to [" + strconv.FormatInt(int64(err.from), 10) + ";" +
-		strconv.FormatInt(int64(err.to), 10) + "] but actual value is " + strconv.FormatInt(int64(err.value), 10)
-}
-
 func (w *huffmanBitWriter) flushBits() {
 	if w.err != nil {
 		w.nbits = 0