diff --git a/message/fmt_test.go b/message/fmt_test.go
new file mode 100644
index 0000000..7f2db5e
--- /dev/null
+++ b/message/fmt_test.go
@@ -0,0 +1,1814 @@
+// +build ignore
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fmt_test
+
+import (
+	"bytes"
+	. "fmt"
+	"internal/race"
+	"math"
+	"reflect"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+	"unicode"
+)
+
+type (
+	renamedBool       bool
+	renamedInt        int
+	renamedInt8       int8
+	renamedInt16      int16
+	renamedInt32      int32
+	renamedInt64      int64
+	renamedUint       uint
+	renamedUint8      uint8
+	renamedUint16     uint16
+	renamedUint32     uint32
+	renamedUint64     uint64
+	renamedUintptr    uintptr
+	renamedString     string
+	renamedBytes      []byte
+	renamedFloat32    float32
+	renamedFloat64    float64
+	renamedComplex64  complex64
+	renamedComplex128 complex128
+)
+
+func TestFmtInterface(t *testing.T) {
+	var i1 interface{}
+	i1 = "abc"
+	s := Sprintf("%s", i1)
+	if s != "abc" {
+		t.Errorf(`Sprintf("%%s", empty("abc")) = %q want %q`, s, "abc")
+	}
+}
+
+var (
+	NaN    = math.NaN()
+	posInf = math.Inf(1)
+	negInf = math.Inf(-1)
+
+	intVar = 0
+
+	array  = [5]int{1, 2, 3, 4, 5}
+	iarray = [4]interface{}{1, "hello", 2.5, nil}
+	slice  = array[:]
+	islice = iarray[:]
+)
+
+type A struct {
+	i int
+	j uint
+	s string
+	x []int
+}
+
+type I int
+
+func (i I) String() string { return Sprintf("<%d>", int(i)) }
+
+type B struct {
+	I I
+	j int
+}
+
+type C struct {
+	i int
+	B
+}
+
+type F int
+
+func (f F) Format(s State, c rune) {
+	Fprintf(s, "<%c=F(%d)>", c, int(f))
+}
+
+type G int
+
+func (g G) GoString() string {
+	return Sprintf("GoString(%d)", int(g))
+}
+
+type S struct {
+	F F // a struct field that Formats
+	G G // a struct field that GoStrings
+}
+
+type SI struct {
+	I interface{}
+}
+
+// P is a type with a String method with pointer receiver for testing %p.
+type P int
+
+var pValue P
+
+func (p *P) String() string {
+	return "String(p)"
+}
+
+var barray = [5]renamedUint8{1, 2, 3, 4, 5}
+var bslice = barray[:]
+
+type byteStringer byte
+
+func (byteStringer) String() string {
+	return "X"
+}
+
+var byteStringerSlice = []byteStringer{'h', 'e', 'l', 'l', 'o'}
+
+type byteFormatter byte
+
+func (byteFormatter) Format(f State, _ rune) {
+	Fprint(f, "X")
+}
+
+var byteFormatterSlice = []byteFormatter{'h', 'e', 'l', 'l', 'o'}
+
+var fmtTests = []struct {
+	fmt string
+	val interface{}
+	out string
+}{
+	{"%d", 12345, "12345"},
+	{"%v", 12345, "12345"},
+	{"%t", true, "true"},
+
+	// basic string
+	{"%s", "abc", "abc"},
+	{"%q", "abc", `"abc"`},
+	{"%x", "abc", "616263"},
+	{"%x", "\xff\xf0\x0f\xff", "fff00fff"},
+	{"%X", "\xff\xf0\x0f\xff", "FFF00FFF"},
+	{"%x", "", ""},
+	{"% x", "", ""},
+	{"%#x", "", ""},
+	{"%# x", "", ""},
+	{"%x", "xyz", "78797a"},
+	{"%X", "xyz", "78797A"},
+	{"% x", "xyz", "78 79 7a"},
+	{"% X", "xyz", "78 79 7A"},
+	{"%#x", "xyz", "0x78797a"},
+	{"%#X", "xyz", "0X78797A"},
+	{"%# x", "xyz", "0x78 0x79 0x7a"},
+	{"%# X", "xyz", "0X78 0X79 0X7A"},
+
+	// basic bytes
+	{"%s", []byte("abc"), "abc"},
+	{"%s", [3]byte{'a', 'b', 'c'}, "abc"},
+	{"%s", &[3]byte{'a', 'b', 'c'}, "&abc"},
+	{"%q", []byte("abc"), `"abc"`},
+	{"%x", []byte("abc"), "616263"},
+	{"%x", []byte("\xff\xf0\x0f\xff"), "fff00fff"},
+	{"%X", []byte("\xff\xf0\x0f\xff"), "FFF00FFF"},
+	{"%x", []byte(""), ""},
+	{"% x", []byte(""), ""},
+	{"%#x", []byte(""), ""},
+	{"%# x", []byte(""), ""},
+	{"%x", []byte("xyz"), "78797a"},
+	{"%X", []byte("xyz"), "78797A"},
+	{"% x", []byte("xyz"), "78 79 7a"},
+	{"% X", []byte("xyz"), "78 79 7A"},
+	{"%#x", []byte("xyz"), "0x78797a"},
+	{"%#X", []byte("xyz"), "0X78797A"},
+	{"%# x", []byte("xyz"), "0x78 0x79 0x7a"},
+	{"%# X", []byte("xyz"), "0X78 0X79 0X7A"},
+
+	// escaped strings
+	{"%q", "", `""`},
+	{"%#q", "", "``"},
+	{"%q", "\"", `"\""`},
+	{"%#q", "\"", "`\"`"},
+	{"%q", "`", `"` + "`" + `"`},
+	{"%#q", "`", `"` + "`" + `"`},
+	{"%q", "\n", `"\n"`},
+	{"%#q", "\n", `"\n"`},
+	{"%q", `\n`, `"\\n"`},
+	{"%#q", `\n`, "`\\n`"},
+	{"%q", "abc", `"abc"`},
+	{"%#q", "abc", "`abc`"},
+	{"%q", "日本語", `"日本語"`},
+	{"%+q", "日本語", `"\u65e5\u672c\u8a9e"`},
+	{"%#q", "日本語", "`日本語`"},
+	{"%#+q", "日本語", "`日本語`"},
+	{"%q", "\a\b\f\n\r\t\v\"\\", `"\a\b\f\n\r\t\v\"\\"`},
+	{"%+q", "\a\b\f\n\r\t\v\"\\", `"\a\b\f\n\r\t\v\"\\"`},
+	{"%#q", "\a\b\f\n\r\t\v\"\\", `"\a\b\f\n\r\t\v\"\\"`},
+	{"%#+q", "\a\b\f\n\r\t\v\"\\", `"\a\b\f\n\r\t\v\"\\"`},
+	{"%q", "☺", `"☺"`},
+	{"% q", "☺", `"☺"`}, // The space modifier should have no effect.
+	{"%+q", "☺", `"\u263a"`},
+	{"%#q", "☺", "`☺`"},
+	{"%#+q", "☺", "`☺`"},
+	{"%10q", "⌘", `       "⌘"`},
+	{"%+10q", "⌘", `  "\u2318"`},
+	{"%-10q", "⌘", `"⌘"       `},
+	{"%+-10q", "⌘", `"\u2318"  `},
+	{"%010q", "⌘", `0000000"⌘"`},
+	{"%+010q", "⌘", `00"\u2318"`},
+	{"%-010q", "⌘", `"⌘"       `}, // 0 has no effect when - is present.
+	{"%+-010q", "⌘", `"\u2318"  `},
+	{"%#8q", "\n", `    "\n"`},
+	{"%#+8q", "\r", `    "\r"`},
+	{"%#-8q", "\t", "`	`     "},
+	{"%#+-8q", "\b", `"\b"    `},
+	{"%q", "abc\xffdef", `"abc\xffdef"`},
+	{"%+q", "abc\xffdef", `"abc\xffdef"`},
+	{"%#q", "abc\xffdef", `"abc\xffdef"`},
+	{"%#+q", "abc\xffdef", `"abc\xffdef"`},
+	// Runes that are not printable.
+	{"%q", "\U0010ffff", `"\U0010ffff"`},
+	{"%+q", "\U0010ffff", `"\U0010ffff"`},
+	{"%#q", "\U0010ffff", "`􏿿`"},
+	{"%#+q", "\U0010ffff", "`􏿿`"},
+	// Runes that are not valid.
+	{"%q", string(0x110000), `"�"`},
+	{"%+q", string(0x110000), `"\ufffd"`},
+	{"%#q", string(0x110000), "`�`"},
+	{"%#+q", string(0x110000), "`�`"},
+
+	// characters
+	{"%c", uint('x'), "x"},
+	{"%c", 0xe4, "ä"},
+	{"%c", 0x672c, "本"},
+	{"%c", '日', "日"},
+	{"%.0c", '⌘', "⌘"}, // Specifying precision should have no effect.
+	{"%3c", '⌘', "  ⌘"},
+	{"%-3c", '⌘', "⌘  "},
+	// Runes that are not printable.
+	{"%c", '\U00000e00', "\u0e00"},
+	{"%c", '\U0010ffff', "\U0010ffff"},
+	// Runes that are not valid.
+	{"%c", -1, "�"},
+	{"%c", 0xDC80, "�"},
+	{"%c", rune(0x110000), "�"},
+	{"%c", int64(0xFFFFFFFFF), "�"},
+	{"%c", uint64(0xFFFFFFFFF), "�"},
+
+	// escaped characters
+	{"%q", uint(0), `'\x00'`},
+	{"%+q", uint(0), `'\x00'`},
+	{"%q", '"', `'"'`},
+	{"%+q", '"', `'"'`},
+	{"%q", '\'', `'\''`},
+	{"%+q", '\'', `'\''`},
+	{"%q", '`', "'`'"},
+	{"%+q", '`', "'`'"},
+	{"%q", 'x', `'x'`},
+	{"%+q", 'x', `'x'`},
+	{"%q", 'ÿ', `'ÿ'`},
+	{"%+q", 'ÿ', `'\u00ff'`},
+	{"%q", '\n', `'\n'`},
+	{"%+q", '\n', `'\n'`},
+	{"%q", '☺', `'☺'`},
+	{"%+q", '☺', `'\u263a'`},
+	{"% q", '☺', `'☺'`},  // The space modifier should have no effect.
+	{"%.0q", '☺', `'☺'`}, // Specifying precision should have no effect.
+	{"%10q", '⌘', `       '⌘'`},
+	{"%+10q", '⌘', `  '\u2318'`},
+	{"%-10q", '⌘', `'⌘'       `},
+	{"%+-10q", '⌘', `'\u2318'  `},
+	{"%010q", '⌘', `0000000'⌘'`},
+	{"%+010q", '⌘', `00'\u2318'`},
+	{"%-010q", '⌘', `'⌘'       `}, // 0 has no effect when - is present.
+	{"%+-010q", '⌘', `'\u2318'  `},
+	// Runes that are not printable.
+	{"%q", '\U00000e00', `'\u0e00'`},
+	{"%q", '\U0010ffff', `'\U0010ffff'`},
+	// Runes that are not valid.
+	{"%q", int32(-1), "%!q(int32=-1)"},
+	{"%q", 0xDC80, `'�'`},
+	{"%q", rune(0x110000), "%!q(int32=1114112)"},
+	{"%q", int64(0xFFFFFFFFF), "%!q(int64=68719476735)"},
+	{"%q", uint64(0xFFFFFFFFF), "%!q(uint64=68719476735)"},
+
+	// width
+	{"%5s", "abc", "  abc"},
+	{"%2s", "\u263a", " ☺"},
+	{"%-5s", "abc", "abc  "},
+	{"%-8q", "abc", `"abc"   `},
+	{"%05s", "abc", "00abc"},
+	{"%08q", "abc", `000"abc"`},
+	{"%5s", "abcdefghijklmnopqrstuvwxyz", "abcdefghijklmnopqrstuvwxyz"},
+	{"%.5s", "abcdefghijklmnopqrstuvwxyz", "abcde"},
+	{"%.0s", "日本語日本語", ""},
+	{"%.5s", "日本語日本語", "日本語日本"},
+	{"%.10s", "日本語日本語", "日本語日本語"},
+	{"%.5s", []byte("日本語日本語"), "日本語日本"},
+	{"%.5q", "abcdefghijklmnopqrstuvwxyz", `"abcde"`},
+	{"%.5x", "abcdefghijklmnopqrstuvwxyz", "6162636465"},
+	{"%.5q", []byte("abcdefghijklmnopqrstuvwxyz"), `"abcde"`},
+	{"%.5x", []byte("abcdefghijklmnopqrstuvwxyz"), "6162636465"},
+	{"%.3q", "日本語日本語", `"日本語"`},
+	{"%.3q", []byte("日本語日本語"), `"日本語"`},
+	{"%.1q", "日本語", `"日"`},
+	{"%.1q", []byte("日本語"), `"日"`},
+	{"%.1x", "日本語", "e6"},
+	{"%.1X", []byte("日本語"), "E6"},
+	{"%10.1q", "日本語日本語", `       "日"`},
+	{"%10v", nil, "     <nil>"},
+	{"%-10v", nil, "<nil>     "},
+
+	// integers
+	{"%d", uint(12345), "12345"},
+	{"%d", int(-12345), "-12345"},
+	{"%d", ^uint8(0), "255"},
+	{"%d", ^uint16(0), "65535"},
+	{"%d", ^uint32(0), "4294967295"},
+	{"%d", ^uint64(0), "18446744073709551615"},
+	{"%d", int8(-1 << 7), "-128"},
+	{"%d", int16(-1 << 15), "-32768"},
+	{"%d", int32(-1 << 31), "-2147483648"},
+	{"%d", int64(-1 << 63), "-9223372036854775808"},
+	{"%.d", 0, ""},
+	{"%.0d", 0, ""},
+	{"%6.0d", 0, "      "},
+	{"%06.0d", 0, "      "},
+	{"% d", 12345, " 12345"},
+	{"%+d", 12345, "+12345"},
+	{"%+d", -12345, "-12345"},
+	{"%b", 7, "111"},
+	{"%b", -6, "-110"},
+	{"%b", ^uint32(0), "11111111111111111111111111111111"},
+	{"%b", ^uint64(0), "1111111111111111111111111111111111111111111111111111111111111111"},
+	{"%b", int64(-1 << 63), zeroFill("-1", 63, "")},
+	{"%o", 01234, "1234"},
+	{"%#o", 01234, "01234"},
+	{"%o", ^uint32(0), "37777777777"},
+	{"%o", ^uint64(0), "1777777777777777777777"},
+	{"%#X", 0, "0X0"},
+	{"%x", 0x12abcdef, "12abcdef"},
+	{"%X", 0x12abcdef, "12ABCDEF"},
+	{"%x", ^uint32(0), "ffffffff"},
+	{"%X", ^uint64(0), "FFFFFFFFFFFFFFFF"},
+	{"%.20b", 7, "00000000000000000111"},
+	{"%10d", 12345, "     12345"},
+	{"%10d", -12345, "    -12345"},
+	{"%+10d", 12345, "    +12345"},
+	{"%010d", 12345, "0000012345"},
+	{"%010d", -12345, "-000012345"},
+	{"%20.8d", 1234, "            00001234"},
+	{"%20.8d", -1234, "           -00001234"},
+	{"%020.8d", 1234, "            00001234"},
+	{"%020.8d", -1234, "           -00001234"},
+	{"%-20.8d", 1234, "00001234            "},
+	{"%-20.8d", -1234, "-00001234           "},
+	{"%-#20.8x", 0x1234abc, "0x01234abc          "},
+	{"%-#20.8X", 0x1234abc, "0X01234ABC          "},
+	{"%-#20.8o", 01234, "00001234            "},
+
+	// Test correct f.intbuf overflow checks.
+	{"%068d", 1, zeroFill("", 68, "1")},
+	{"%068d", -1, zeroFill("-", 67, "1")},
+	{"%#.68x", 42, zeroFill("0x", 68, "2a")},
+	{"%.68d", -42, zeroFill("-", 68, "42")},
+	{"%+.68d", 42, zeroFill("+", 68, "42")},
+	{"% .68d", 42, zeroFill(" ", 68, "42")},
+	{"% +.68d", 42, zeroFill("+", 68, "42")},
+
+	// unicode format
+	{"%U", 0, "U+0000"},
+	{"%U", -1, "U+FFFFFFFFFFFFFFFF"},
+	{"%U", '\n', `U+000A`},
+	{"%#U", '\n', `U+000A`},
+	{"%+U", 'x', `U+0078`},       // Plus flag should have no effect.
+	{"%# U", 'x', `U+0078 'x'`},  // Space flag should have no effect.
+	{"%#.2U", 'x', `U+0078 'x'`}, // Precisions below 4 should print 4 digits.
+	{"%U", '\u263a', `U+263A`},
+	{"%#U", '\u263a', `U+263A '☺'`},
+	{"%U", '\U0001D6C2', `U+1D6C2`},
+	{"%#U", '\U0001D6C2', `U+1D6C2 '𝛂'`},
+	{"%#14.6U", '⌘', "  U+002318 '⌘'"},
+	{"%#-14.6U", '⌘', "U+002318 '⌘'  "},
+	{"%#014.6U", '⌘', "  U+002318 '⌘'"},
+	{"%#-014.6U", '⌘', "U+002318 '⌘'  "},
+	{"%.68U", uint(42), zeroFill("U+", 68, "2A")},
+	{"%#.68U", '日', zeroFill("U+", 68, "65E5") + " '日'"},
+
+	// floats
+	{"%+.3e", 0.0, "+0.000e+00"},
+	{"%+.3e", 1.0, "+1.000e+00"},
+	{"%+.3f", -1.0, "-1.000"},
+	{"%+.3F", -1.0, "-1.000"},
+	{"%+.3F", float32(-1.0), "-1.000"},
+	{"%+07.2f", 1.0, "+001.00"},
+	{"%+07.2f", -1.0, "-001.00"},
+	{"%-07.2f", 1.0, "1.00   "},
+	{"%-07.2f", -1.0, "-1.00  "},
+	{"%+-07.2f", 1.0, "+1.00  "},
+	{"%+-07.2f", -1.0, "-1.00  "},
+	{"%-+07.2f", 1.0, "+1.00  "},
+	{"%-+07.2f", -1.0, "-1.00  "},
+	{"%+10.2f", +1.0, "     +1.00"},
+	{"%+10.2f", -1.0, "     -1.00"},
+	{"% .3E", -1.0, "-1.000E+00"},
+	{"% .3e", 1.0, " 1.000e+00"},
+	{"%+.3g", 0.0, "+0"},
+	{"%+.3g", 1.0, "+1"},
+	{"%+.3g", -1.0, "-1"},
+	{"% .3g", -1.0, "-1"},
+	{"% .3g", 1.0, " 1"},
+	{"%b", float32(1.0), "8388608p-23"},
+	{"%b", 1.0, "4503599627370496p-52"},
+	// Test sharp flag used with floats.
+	{"%#g", 1e-323, "1.00000e-323"},
+	{"%#g", -1.0, "-1.00000"},
+	{"%#g", 1.1, "1.10000"},
+	{"%#g", 123456.0, "123456."},
+	{"%#g", 1234567.0, "1.234567e+06"},
+	{"%#g", 1230000.0, "1.23000e+06"},
+	{"%#g", 1000000.0, "1.00000e+06"},
+	{"%#.0f", 1.0, "1."},
+	{"%#.0e", 1.0, "1.e+00"},
+	{"%#.0g", 1.0, "1."},
+	{"%#.0g", 1100000.0, "1.e+06"},
+	{"%#.4f", 1.0, "1.0000"},
+	{"%#.4e", 1.0, "1.0000e+00"},
+	{"%#.4g", 1.0, "1.000"},
+	{"%#.4g", 100000.0, "1.000e+05"},
+	{"%#.0f", 123.0, "123."},
+	{"%#.0e", 123.0, "1.e+02"},
+	{"%#.0g", 123.0, "1.e+02"},
+	{"%#.4f", 123.0, "123.0000"},
+	{"%#.4e", 123.0, "1.2300e+02"},
+	{"%#.4g", 123.0, "123.0"},
+	{"%#.4g", 123000.0, "1.230e+05"},
+	{"%#9.4g", 1.0, "    1.000"},
+	// The sharp flag has no effect for binary float format.
+	{"%#b", 1.0, "4503599627370496p-52"},
+	// Precision has no effect for binary float format.
+	{"%.4b", float32(1.0), "8388608p-23"},
+	{"%.4b", -1.0, "-4503599627370496p-52"},
+	// Test correct f.intbuf boundary checks.
+	{"%.68f", 1.0, zeroFill("1.", 68, "")},
+	{"%.68f", -1.0, zeroFill("-1.", 68, "")},
+	// float infinites and NaNs
+	{"%f", posInf, "+Inf"},
+	{"%.1f", negInf, "-Inf"},
+	{"% f", NaN, " NaN"},
+	{"%20f", posInf, "                +Inf"},
+	{"% 20F", posInf, "                 Inf"},
+	{"% 20e", negInf, "                -Inf"},
+	{"%+20E", negInf, "                -Inf"},
+	{"% +20g", negInf, "                -Inf"},
+	{"%+-20G", posInf, "+Inf                "},
+	{"%20e", NaN, "                 NaN"},
+	{"% +20E", NaN, "                +NaN"},
+	{"% -20g", NaN, " NaN                "},
+	{"%+-20G", NaN, "+NaN                "},
+	// Zero padding does not apply to infinities and NaN.
+	{"%+020e", posInf, "                +Inf"},
+	{"%-020f", negInf, "-Inf                "},
+	{"%-020E", NaN, "NaN                 "},
+
+	// complex values
+	{"%.f", 0i, "(0+0i)"},
+	{"% .f", 0i, "( 0+0i)"},
+	{"%+.f", 0i, "(+0+0i)"},
+	{"% +.f", 0i, "(+0+0i)"},
+	{"%+.3e", 0i, "(+0.000e+00+0.000e+00i)"},
+	{"%+.3f", 0i, "(+0.000+0.000i)"},
+	{"%+.3g", 0i, "(+0+0i)"},
+	{"%+.3e", 1 + 2i, "(+1.000e+00+2.000e+00i)"},
+	{"%+.3f", 1 + 2i, "(+1.000+2.000i)"},
+	{"%+.3g", 1 + 2i, "(+1+2i)"},
+	{"%.3e", 0i, "(0.000e+00+0.000e+00i)"},
+	{"%.3f", 0i, "(0.000+0.000i)"},
+	{"%.3F", 0i, "(0.000+0.000i)"},
+	{"%.3F", complex64(0i), "(0.000+0.000i)"},
+	{"%.3g", 0i, "(0+0i)"},
+	{"%.3e", 1 + 2i, "(1.000e+00+2.000e+00i)"},
+	{"%.3f", 1 + 2i, "(1.000+2.000i)"},
+	{"%.3g", 1 + 2i, "(1+2i)"},
+	{"%.3e", -1 - 2i, "(-1.000e+00-2.000e+00i)"},
+	{"%.3f", -1 - 2i, "(-1.000-2.000i)"},
+	{"%.3g", -1 - 2i, "(-1-2i)"},
+	{"% .3E", -1 - 2i, "(-1.000E+00-2.000E+00i)"},
+	{"%+.3g", 1 + 2i, "(+1+2i)"},
+	{"%+.3g", complex64(1 + 2i), "(+1+2i)"},
+	{"%#g", 1 + 2i, "(1.00000+2.00000i)"},
+	{"%#g", 123456 + 789012i, "(123456.+789012.i)"},
+	{"%#g", 1e-10i, "(0.00000+1.00000e-10i)"},
+	{"%#g", -1e10 - 1.11e100i, "(-1.00000e+10-1.11000e+100i)"},
+	{"%#.0f", 1.23 + 1.0i, "(1.+1.i)"},
+	{"%#.0e", 1.23 + 1.0i, "(1.e+00+1.e+00i)"},
+	{"%#.0g", 1.23 + 1.0i, "(1.+1.i)"},
+	{"%#.0g", 0 + 100000i, "(0.+1.e+05i)"},
+	{"%#.0g", 1230000 + 0i, "(1.e+06+0.i)"},
+	{"%#.4f", 1 + 1.23i, "(1.0000+1.2300i)"},
+	{"%#.4e", 123 + 1i, "(1.2300e+02+1.0000e+00i)"},
+	{"%#.4g", 123 + 1.23i, "(123.0+1.230i)"},
+	{"%#12.5g", 0 + 100000i, "(      0.0000 +1.0000e+05i)"},
+	{"%#12.5g", 1230000 - 0i, "(  1.2300e+06     +0.0000i)"},
+	{"%b", 1 + 2i, "(4503599627370496p-52+4503599627370496p-51i)"},
+	{"%b", complex64(1 + 2i), "(8388608p-23+8388608p-22i)"},
+	// The sharp flag has no effect for binary complex format.
+	{"%#b", 1 + 2i, "(4503599627370496p-52+4503599627370496p-51i)"},
+	// Precision has no effect for binary complex format.
+	{"%.4b", 1 + 2i, "(4503599627370496p-52+4503599627370496p-51i)"},
+	{"%.4b", complex64(1 + 2i), "(8388608p-23+8388608p-22i)"},
+	// complex infinites and NaNs
+	{"%f", complex(posInf, posInf), "(+Inf+Infi)"},
+	{"%f", complex(negInf, negInf), "(-Inf-Infi)"},
+	{"%f", complex(NaN, NaN), "(NaN+NaNi)"},
+	{"%.1f", complex(posInf, posInf), "(+Inf+Infi)"},
+	{"% f", complex(posInf, posInf), "( Inf+Infi)"},
+	{"% f", complex(negInf, negInf), "(-Inf-Infi)"},
+	{"% f", complex(NaN, NaN), "( NaN+NaNi)"},
+	{"%8e", complex(posInf, posInf), "(    +Inf    +Infi)"},
+	{"% 8E", complex(posInf, posInf), "(     Inf    +Infi)"},
+	{"%+8f", complex(negInf, negInf), "(    -Inf    -Infi)"},
+	{"% +8g", complex(negInf, negInf), "(    -Inf    -Infi)"},
+	{"% -8G", complex(NaN, NaN), "( NaN    +NaN    i)"},
+	{"%+-8b", complex(NaN, NaN), "(+NaN    +NaN    i)"},
+	// Zero padding does not apply to infinities and NaN.
+	{"%08f", complex(posInf, posInf), "(    +Inf    +Infi)"},
+	{"%-08g", complex(negInf, negInf), "(-Inf    -Inf    i)"},
+	{"%-08G", complex(NaN, NaN), "(NaN     +NaN    i)"},
+
+	// old test/fmt_test.go
+	{"%e", 1.0, "1.000000e+00"},
+	{"%e", 1234.5678e3, "1.234568e+06"},
+	{"%e", 1234.5678e-8, "1.234568e-05"},
+	{"%e", -7.0, "-7.000000e+00"},
+	{"%e", -1e-9, "-1.000000e-09"},
+	{"%f", 1234.5678e3, "1234567.800000"},
+	{"%f", 1234.5678e-8, "0.000012"},
+	{"%f", -7.0, "-7.000000"},
+	{"%f", -1e-9, "-0.000000"},
+	{"%g", 1234.5678e3, "1.2345678e+06"},
+	{"%g", float32(1234.5678e3), "1.2345678e+06"},
+	{"%g", 1234.5678e-8, "1.2345678e-05"},
+	{"%g", -7.0, "-7"},
+	{"%g", -1e-9, "-1e-09"},
+	{"%g", float32(-1e-9), "-1e-09"},
+	{"%E", 1.0, "1.000000E+00"},
+	{"%E", 1234.5678e3, "1.234568E+06"},
+	{"%E", 1234.5678e-8, "1.234568E-05"},
+	{"%E", -7.0, "-7.000000E+00"},
+	{"%E", -1e-9, "-1.000000E-09"},
+	{"%G", 1234.5678e3, "1.2345678E+06"},
+	{"%G", float32(1234.5678e3), "1.2345678E+06"},
+	{"%G", 1234.5678e-8, "1.2345678E-05"},
+	{"%G", -7.0, "-7"},
+	{"%G", -1e-9, "-1E-09"},
+	{"%G", float32(-1e-9), "-1E-09"},
+	{"%20.5s", "qwertyuiop", "               qwert"},
+	{"%.5s", "qwertyuiop", "qwert"},
+	{"%-20.5s", "qwertyuiop", "qwert               "},
+	{"%20c", 'x', "                   x"},
+	{"%-20c", 'x', "x                   "},
+	{"%20.6e", 1.2345e3, "        1.234500e+03"},
+	{"%20.6e", 1.2345e-3, "        1.234500e-03"},
+	{"%20e", 1.2345e3, "        1.234500e+03"},
+	{"%20e", 1.2345e-3, "        1.234500e-03"},
+	{"%20.8e", 1.2345e3, "      1.23450000e+03"},
+	{"%20f", 1.23456789e3, "         1234.567890"},
+	{"%20f", 1.23456789e-3, "            0.001235"},
+	{"%20f", 12345678901.23456789, "  12345678901.234568"},
+	{"%-20f", 1.23456789e3, "1234.567890         "},
+	{"%20.8f", 1.23456789e3, "       1234.56789000"},
+	{"%20.8f", 1.23456789e-3, "          0.00123457"},
+	{"%g", 1.23456789e3, "1234.56789"},
+	{"%g", 1.23456789e-3, "0.00123456789"},
+	{"%g", 1.23456789e20, "1.23456789e+20"},
+
+	// arrays
+	{"%v", array, "[1 2 3 4 5]"},
+	{"%v", iarray, "[1 hello 2.5 <nil>]"},
+	{"%v", barray, "[1 2 3 4 5]"},
+	{"%v", &array, "&[1 2 3 4 5]"},
+	{"%v", &iarray, "&[1 hello 2.5 <nil>]"},
+	{"%v", &barray, "&[1 2 3 4 5]"},
+
+	// slices
+	{"%v", slice, "[1 2 3 4 5]"},
+	{"%v", islice, "[1 hello 2.5 <nil>]"},
+	{"%v", bslice, "[1 2 3 4 5]"},
+	{"%v", &slice, "&[1 2 3 4 5]"},
+	{"%v", &islice, "&[1 hello 2.5 <nil>]"},
+	{"%v", &bslice, "&[1 2 3 4 5]"},
+
+	// byte arrays and slices with %b,%c,%d,%o,%U and %v
+	{"%b", [3]byte{65, 66, 67}, "[1000001 1000010 1000011]"},
+	{"%c", [3]byte{65, 66, 67}, "[A B C]"},
+	{"%d", [3]byte{65, 66, 67}, "[65 66 67]"},
+	{"%o", [3]byte{65, 66, 67}, "[101 102 103]"},
+	{"%U", [3]byte{65, 66, 67}, "[U+0041 U+0042 U+0043]"},
+	{"%v", [3]byte{65, 66, 67}, "[65 66 67]"},
+	{"%v", [1]byte{123}, "[123]"},
+	{"%012v", []byte{}, "[]"},
+	{"%#012v", []byte{}, "[]byte{}"},
+	{"%6v", []byte{1, 11, 111}, "[     1     11    111]"},
+	{"%06v", []byte{1, 11, 111}, "[000001 000011 000111]"},
+	{"%-6v", []byte{1, 11, 111}, "[1      11     111   ]"},
+	{"%-06v", []byte{1, 11, 111}, "[1      11     111   ]"},
+	{"%#v", []byte{1, 11, 111}, "[]byte{0x1, 0xb, 0x6f}"},
+	{"%#6v", []byte{1, 11, 111}, "[]byte{   0x1,    0xb,   0x6f}"},
+	{"%#06v", []byte{1, 11, 111}, "[]byte{0x000001, 0x00000b, 0x00006f}"},
+	{"%#-6v", []byte{1, 11, 111}, "[]byte{0x1   , 0xb   , 0x6f  }"},
+	{"%#-06v", []byte{1, 11, 111}, "[]byte{0x1   , 0xb   , 0x6f  }"},
+	// f.space should and f.plus should not have an effect with %v.
+	{"% v", []byte{1, 11, 111}, "[ 1  11  111]"},
+	{"%+v", [3]byte{1, 11, 111}, "[1 11 111]"},
+	{"%# -6v", []byte{1, 11, 111}, "[]byte{ 0x1  ,  0xb  ,  0x6f }"},
+	{"%#+-6v", [3]byte{1, 11, 111}, "[3]uint8{0x1   , 0xb   , 0x6f  }"},
+	// f.space and f.plus should have an effect with %d.
+	{"% d", []byte{1, 11, 111}, "[ 1  11  111]"},
+	{"%+d", [3]byte{1, 11, 111}, "[+1 +11 +111]"},
+	{"%# -6d", []byte{1, 11, 111}, "[ 1      11     111  ]"},
+	{"%#+-6d", [3]byte{1, 11, 111}, "[+1     +11    +111  ]"},
+
+	// floates with %v
+	{"%v", 1.2345678, "1.2345678"},
+	{"%v", float32(1.2345678), "1.2345678"},
+
+	// complexes with %v
+	{"%v", 1 + 2i, "(1+2i)"},
+	{"%v", complex64(1 + 2i), "(1+2i)"},
+
+	// structs
+	{"%v", A{1, 2, "a", []int{1, 2}}, `{1 2 a [1 2]}`},
+	{"%+v", A{1, 2, "a", []int{1, 2}}, `{i:1 j:2 s:a x:[1 2]}`},
+
+	// +v on structs with Stringable items
+	{"%+v", B{1, 2}, `{I:<1> j:2}`},
+	{"%+v", C{1, B{2, 3}}, `{i:1 B:{I:<2> j:3}}`},
+
+	// other formats on Stringable items
+	{"%s", I(23), `<23>`},
+	{"%q", I(23), `"<23>"`},
+	{"%x", I(23), `3c32333e`},
+	{"%#x", I(23), `0x3c32333e`},
+	{"%# x", I(23), `0x3c 0x32 0x33 0x3e`},
+	// Stringer applies only to string formats.
+	{"%d", I(23), `23`},
+	// Stringer applies to the extracted value.
+	{"%s", reflect.ValueOf(I(23)), `<23>`},
+
+	// go syntax
+	{"%#v", A{1, 2, "a", []int{1, 2}}, `fmt_test.A{i:1, j:0x2, s:"a", x:[]int{1, 2}}`},
+	{"%#v", new(byte), "(*uint8)(0xPTR)"},
+	{"%#v", TestFmtInterface, "(func(*testing.T))(0xPTR)"},
+	{"%#v", make(chan int), "(chan int)(0xPTR)"},
+	{"%#v", uint64(1<<64 - 1), "0xffffffffffffffff"},
+	{"%#v", 1000000000, "1000000000"},
+	{"%#v", map[string]int{"a": 1}, `map[string]int{"a":1}`},
+	{"%#v", map[string]B{"a": {1, 2}}, `map[string]fmt_test.B{"a":fmt_test.B{I:1, j:2}}`},
+	{"%#v", []string{"a", "b"}, `[]string{"a", "b"}`},
+	{"%#v", SI{}, `fmt_test.SI{I:interface {}(nil)}`},
+	{"%#v", []int(nil), `[]int(nil)`},
+	{"%#v", []int{}, `[]int{}`},
+	{"%#v", array, `[5]int{1, 2, 3, 4, 5}`},
+	{"%#v", &array, `&[5]int{1, 2, 3, 4, 5}`},
+	{"%#v", iarray, `[4]interface {}{1, "hello", 2.5, interface {}(nil)}`},
+	{"%#v", &iarray, `&[4]interface {}{1, "hello", 2.5, interface {}(nil)}`},
+	{"%#v", map[int]byte(nil), `map[int]uint8(nil)`},
+	{"%#v", map[int]byte{}, `map[int]uint8{}`},
+	{"%#v", "foo", `"foo"`},
+	{"%#v", barray, `[5]fmt_test.renamedUint8{0x1, 0x2, 0x3, 0x4, 0x5}`},
+	{"%#v", bslice, `[]fmt_test.renamedUint8{0x1, 0x2, 0x3, 0x4, 0x5}`},
+	{"%#v", []int32(nil), "[]int32(nil)"},
+	{"%#v", 1.2345678, "1.2345678"},
+	{"%#v", float32(1.2345678), "1.2345678"},
+	// Only print []byte and []uint8 as type []byte if they appear at the top level.
+	{"%#v", []byte(nil), "[]byte(nil)"},
+	{"%#v", []uint8(nil), "[]byte(nil)"},
+	{"%#v", []byte{}, "[]byte{}"},
+	{"%#v", []uint8{}, "[]byte{}"},
+	{"%#v", reflect.ValueOf([]byte{}), "[]uint8{}"},
+	{"%#v", reflect.ValueOf([]uint8{}), "[]uint8{}"},
+	{"%#v", &[]byte{}, "&[]uint8{}"},
+	{"%#v", &[]byte{}, "&[]uint8{}"},
+	{"%#v", [3]byte{}, "[3]uint8{0x0, 0x0, 0x0}"},
+	{"%#v", [3]uint8{}, "[3]uint8{0x0, 0x0, 0x0}"},
+
+	// slices with other formats
+	{"%#x", []int{1, 2, 15}, `[0x1 0x2 0xf]`},
+	{"%x", []int{1, 2, 15}, `[1 2 f]`},
+	{"%d", []int{1, 2, 15}, `[1 2 15]`},
+	{"%d", []byte{1, 2, 15}, `[1 2 15]`},
+	{"%q", []string{"a", "b"}, `["a" "b"]`},
+	{"% 02x", []byte{1}, "01"},
+	{"% 02x", []byte{1, 2, 3}, "01 02 03"},
+
+	// Padding with byte slices.
+	{"%2x", []byte{}, "  "},
+	{"%#2x", []byte{}, "  "},
+	{"% 02x", []byte{}, "00"},
+	{"%# 02x", []byte{}, "00"},
+	{"%-2x", []byte{}, "  "},
+	{"%-02x", []byte{}, "  "},
+	{"%8x", []byte{0xab}, "      ab"},
+	{"% 8x", []byte{0xab}, "      ab"},
+	{"%#8x", []byte{0xab}, "    0xab"},
+	{"%# 8x", []byte{0xab}, "    0xab"},
+	{"%08x", []byte{0xab}, "000000ab"},
+	{"% 08x", []byte{0xab}, "000000ab"},
+	{"%#08x", []byte{0xab}, "00000xab"},
+	{"%# 08x", []byte{0xab}, "00000xab"},
+	{"%10x", []byte{0xab, 0xcd}, "      abcd"},
+	{"% 10x", []byte{0xab, 0xcd}, "     ab cd"},
+	{"%#10x", []byte{0xab, 0xcd}, "    0xabcd"},
+	{"%# 10x", []byte{0xab, 0xcd}, " 0xab 0xcd"},
+	{"%010x", []byte{0xab, 0xcd}, "000000abcd"},
+	{"% 010x", []byte{0xab, 0xcd}, "00000ab cd"},
+	{"%#010x", []byte{0xab, 0xcd}, "00000xabcd"},
+	{"%# 010x", []byte{0xab, 0xcd}, "00xab 0xcd"},
+	{"%-10X", []byte{0xab}, "AB        "},
+	{"% -010X", []byte{0xab}, "AB        "},
+	{"%#-10X", []byte{0xab, 0xcd}, "0XABCD    "},
+	{"%# -010X", []byte{0xab, 0xcd}, "0XAB 0XCD "},
+	// Same for strings
+	{"%2x", "", "  "},
+	{"%#2x", "", "  "},
+	{"% 02x", "", "00"},
+	{"%# 02x", "", "00"},
+	{"%-2x", "", "  "},
+	{"%-02x", "", "  "},
+	{"%8x", "\xab", "      ab"},
+	{"% 8x", "\xab", "      ab"},
+	{"%#8x", "\xab", "    0xab"},
+	{"%# 8x", "\xab", "    0xab"},
+	{"%08x", "\xab", "000000ab"},
+	{"% 08x", "\xab", "000000ab"},
+	{"%#08x", "\xab", "00000xab"},
+	{"%# 08x", "\xab", "00000xab"},
+	{"%10x", "\xab\xcd", "      abcd"},
+	{"% 10x", "\xab\xcd", "     ab cd"},
+	{"%#10x", "\xab\xcd", "    0xabcd"},
+	{"%# 10x", "\xab\xcd", " 0xab 0xcd"},
+	{"%010x", "\xab\xcd", "000000abcd"},
+	{"% 010x", "\xab\xcd", "00000ab cd"},
+	{"%#010x", "\xab\xcd", "00000xabcd"},
+	{"%# 010x", "\xab\xcd", "00xab 0xcd"},
+	{"%-10X", "\xab", "AB        "},
+	{"% -010X", "\xab", "AB        "},
+	{"%#-10X", "\xab\xcd", "0XABCD    "},
+	{"%# -010X", "\xab\xcd", "0XAB 0XCD "},
+
+	// renamings
+	{"%v", renamedBool(true), "true"},
+	{"%d", renamedBool(true), "%!d(fmt_test.renamedBool=true)"},
+	{"%o", renamedInt(8), "10"},
+	{"%d", renamedInt8(-9), "-9"},
+	{"%v", renamedInt16(10), "10"},
+	{"%v", renamedInt32(-11), "-11"},
+	{"%X", renamedInt64(255), "FF"},
+	{"%v", renamedUint(13), "13"},
+	{"%o", renamedUint8(14), "16"},
+	{"%X", renamedUint16(15), "F"},
+	{"%d", renamedUint32(16), "16"},
+	{"%X", renamedUint64(17), "11"},
+	{"%o", renamedUintptr(18), "22"},
+	{"%x", renamedString("thing"), "7468696e67"},
+	{"%d", renamedBytes([]byte{1, 2, 15}), `[1 2 15]`},
+	{"%q", renamedBytes([]byte("hello")), `"hello"`},
+	{"%x", []renamedUint8{'h', 'e', 'l', 'l', 'o'}, "68656c6c6f"},
+	{"%X", []renamedUint8{'h', 'e', 'l', 'l', 'o'}, "68656C6C6F"},
+	{"%s", []renamedUint8{'h', 'e', 'l', 'l', 'o'}, "hello"},
+	{"%q", []renamedUint8{'h', 'e', 'l', 'l', 'o'}, `"hello"`},
+	{"%v", renamedFloat32(22), "22"},
+	{"%v", renamedFloat64(33), "33"},
+	{"%v", renamedComplex64(3 + 4i), "(3+4i)"},
+	{"%v", renamedComplex128(4 - 3i), "(4-3i)"},
+
+	// Formatter
+	{"%x", F(1), "<x=F(1)>"},
+	{"%x", G(2), "2"},
+	{"%+v", S{F(4), G(5)}, "{F:<v=F(4)> G:5}"},
+
+	// GoStringer
+	{"%#v", G(6), "GoString(6)"},
+	{"%#v", S{F(7), G(8)}, "fmt_test.S{F:<v=F(7)>, G:GoString(8)}"},
+
+	// %T
+	{"%T", byte(0), "uint8"},
+	{"%T", reflect.ValueOf(nil), "reflect.Value"},
+	{"%T", (4 - 3i), "complex128"},
+	{"%T", renamedComplex128(4 - 3i), "fmt_test.renamedComplex128"},
+	{"%T", intVar, "int"},
+	{"%6T", &intVar, "  *int"},
+	{"%10T", nil, "     <nil>"},
+	{"%-10T", nil, "<nil>     "},
+
+	// %p with pointers
+	{"%p", (*int)(nil), "0x0"},
+	{"%#p", (*int)(nil), "0"},
+	{"%p", &intVar, "0xPTR"},
+	{"%#p", &intVar, "PTR"},
+	{"%p", &array, "0xPTR"},
+	{"%p", &slice, "0xPTR"},
+	{"%8.2p", (*int)(nil), "    0x00"},
+	{"%-20.16p", &intVar, "0xPTR  "},
+	// %p on non-pointers
+	{"%p", make(chan int), "0xPTR"},
+	{"%p", make(map[int]int), "0xPTR"},
+	{"%p", func() {}, "0xPTR"},
+	{"%p", 27, "%!p(int=27)"},  // not a pointer at all
+	{"%p", nil, "%!p(<nil>)"},  // nil on its own has no type ...
+	{"%#p", nil, "%!p(<nil>)"}, // ... and hence is not a pointer type.
+	// pointers with specified base
+	{"%b", &intVar, "PTR_b"},
+	{"%d", &intVar, "PTR_d"},
+	{"%o", &intVar, "PTR_o"},
+	{"%x", &intVar, "PTR_x"},
+	{"%X", &intVar, "PTR_X"},
+	// %v on pointers
+	{"%v", nil, "<nil>"},
+	{"%#v", nil, "<nil>"},
+	{"%v", (*int)(nil), "<nil>"},
+	{"%#v", (*int)(nil), "(*int)(nil)"},
+	{"%v", &intVar, "0xPTR"},
+	{"%#v", &intVar, "(*int)(0xPTR)"},
+	{"%8.2v", (*int)(nil), "   <nil>"},
+	{"%-20.16v", &intVar, "0xPTR  "},
+	// string method on pointer
+	{"%s", &pValue, "String(p)"}, // String method...
+	{"%p", &pValue, "0xPTR"},     // ... is not called with %p.
+
+	// %d on Stringer should give integer if possible
+	{"%s", time.Time{}.Month(), "January"},
+	{"%d", time.Time{}.Month(), "1"},
+
+	// erroneous things
+	{"", nil, "%!(EXTRA <nil>)"},
+	{"", 2, "%!(EXTRA int=2)"},
+	{"no args", "hello", "no args%!(EXTRA string=hello)"},
+	{"%s %", "hello", "hello %!(NOVERB)"},
+	{"%s %.2", "hello", "hello %!(NOVERB)"},
+	{"%017091901790959340919092959340919017929593813360", 0, "%!(NOVERB)%!(EXTRA int=0)"},
+	{"%184467440737095516170v", 0, "%!(NOVERB)%!(EXTRA int=0)"},
+	// Extra argument errors should format without flags set.
+	{"%010.2", "12345", "%!(NOVERB)%!(EXTRA string=12345)"},
+
+	// The "<nil>" show up because maps are printed by
+	// first obtaining a list of keys and then looking up
+	// each key. Since NaNs can be map keys but cannot
+	// be fetched directly, the lookup fails and returns a
+	// zero reflect.Value, which formats as <nil>.
+	// This test is just to check that it shows the two NaNs at all.
+	{"%v", map[float64]int{NaN: 1, NaN: 2}, "map[NaN:<nil> NaN:<nil>]"},
+
+	// Comparison of padding rules with C printf.
+	/*
+		C program:
+		#include <stdio.h>
+
+		char *format[] = {
+			"[%.2f]",
+			"[% .2f]",
+			"[%+.2f]",
+			"[%7.2f]",
+			"[% 7.2f]",
+			"[%+7.2f]",
+			"[% +7.2f]",
+			"[%07.2f]",
+			"[% 07.2f]",
+			"[%+07.2f]",
+			"[% +07.2f]"
+		};
+
+		int main(void) {
+			int i;
+			for(i = 0; i < 11; i++) {
+				printf("%s: ", format[i]);
+				printf(format[i], 1.0);
+				printf(" ");
+				printf(format[i], -1.0);
+				printf("\n");
+			}
+		}
+
+		Output:
+			[%.2f]: [1.00] [-1.00]
+			[% .2f]: [ 1.00] [-1.00]
+			[%+.2f]: [+1.00] [-1.00]
+			[%7.2f]: [   1.00] [  -1.00]
+			[% 7.2f]: [   1.00] [  -1.00]
+			[%+7.2f]: [  +1.00] [  -1.00]
+			[% +7.2f]: [  +1.00] [  -1.00]
+			[%07.2f]: [0001.00] [-001.00]
+			[% 07.2f]: [ 001.00] [-001.00]
+			[%+07.2f]: [+001.00] [-001.00]
+			[% +07.2f]: [+001.00] [-001.00]
+
+	*/
+	{"%.2f", 1.0, "1.00"},
+	{"%.2f", -1.0, "-1.00"},
+	{"% .2f", 1.0, " 1.00"},
+	{"% .2f", -1.0, "-1.00"},
+	{"%+.2f", 1.0, "+1.00"},
+	{"%+.2f", -1.0, "-1.00"},
+	{"%7.2f", 1.0, "   1.00"},
+	{"%7.2f", -1.0, "  -1.00"},
+	{"% 7.2f", 1.0, "   1.00"},
+	{"% 7.2f", -1.0, "  -1.00"},
+	{"%+7.2f", 1.0, "  +1.00"},
+	{"%+7.2f", -1.0, "  -1.00"},
+	{"% +7.2f", 1.0, "  +1.00"},
+	{"% +7.2f", -1.0, "  -1.00"},
+	{"%07.2f", 1.0, "0001.00"},
+	{"%07.2f", -1.0, "-001.00"},
+	{"% 07.2f", 1.0, " 001.00"},
+	{"% 07.2f", -1.0, "-001.00"},
+	{"%+07.2f", 1.0, "+001.00"},
+	{"%+07.2f", -1.0, "-001.00"},
+	{"% +07.2f", 1.0, "+001.00"},
+	{"% +07.2f", -1.0, "-001.00"},
+
+	// Complex numbers: exhaustively tested in TestComplexFormatting.
+	{"%7.2f", 1 + 2i, "(   1.00  +2.00i)"},
+	{"%+07.2f", -1 - 2i, "(-001.00-002.00i)"},
+
+	// Use spaces instead of zero if padding to the right.
+	{"%0-5s", "abc", "abc  "},
+	{"%-05.1f", 1.0, "1.0  "},
+
+	// float and complex formatting should not change the padding width
+	// for other elements. See issue 14642.
+	{"%06v", []interface{}{+10.0, 10}, "[000010 000010]"},
+	{"%06v", []interface{}{-10.0, 10}, "[-00010 000010]"},
+	{"%06v", []interface{}{+10.0 + 10i, 10}, "[(000010+00010i) 000010]"},
+	{"%06v", []interface{}{-10.0 + 10i, 10}, "[(-00010+00010i) 000010]"},
+
+	// integer formatting should not alter padding for other elements.
+	{"%03.6v", []interface{}{1, 2.0, "x"}, "[000001 002 00x]"},
+	{"%03.0v", []interface{}{0, 2.0, "x"}, "[    002 000]"},
+
+	// Complex fmt used to leave the plus flag set for future entries in the array
+	// causing +2+0i and +3+0i instead of 2+0i and 3+0i.
+	{"%v", []complex64{1, 2, 3}, "[(1+0i) (2+0i) (3+0i)]"},
+	{"%v", []complex128{1, 2, 3}, "[(1+0i) (2+0i) (3+0i)]"},
+
+	// Incomplete format specification caused crash.
+	{"%.", 3, "%!.(int=3)"},
+
+	// Padding for complex numbers. Has been bad, then fixed, then bad again.
+	{"%+10.2f", +104.66 + 440.51i, "(   +104.66   +440.51i)"},
+	{"%+10.2f", -104.66 + 440.51i, "(   -104.66   +440.51i)"},
+	{"%+10.2f", +104.66 - 440.51i, "(   +104.66   -440.51i)"},
+	{"%+10.2f", -104.66 - 440.51i, "(   -104.66   -440.51i)"},
+	{"%+010.2f", +104.66 + 440.51i, "(+000104.66+000440.51i)"},
+	{"%+010.2f", -104.66 + 440.51i, "(-000104.66+000440.51i)"},
+	{"%+010.2f", +104.66 - 440.51i, "(+000104.66-000440.51i)"},
+	{"%+010.2f", -104.66 - 440.51i, "(-000104.66-000440.51i)"},
+
+	// []T where type T is a byte with a Stringer method.
+	{"%v", byteStringerSlice, "[X X X X X]"},
+	{"%s", byteStringerSlice, "hello"},
+	{"%q", byteStringerSlice, "\"hello\""},
+	{"%x", byteStringerSlice, "68656c6c6f"},
+	{"%X", byteStringerSlice, "68656C6C6F"},
+	{"%#v", byteStringerSlice, "[]fmt_test.byteStringer{0x68, 0x65, 0x6c, 0x6c, 0x6f}"},
+
+	// And the same for Formatter.
+	{"%v", byteFormatterSlice, "[X X X X X]"},
+	{"%s", byteFormatterSlice, "hello"},
+	{"%q", byteFormatterSlice, "\"hello\""},
+	{"%x", byteFormatterSlice, "68656c6c6f"},
+	{"%X", byteFormatterSlice, "68656C6C6F"},
+	// This next case seems wrong, but the docs say the Formatter wins here.
+	{"%#v", byteFormatterSlice, "[]fmt_test.byteFormatter{X, X, X, X, X}"},
+
+	// reflect.Value handled specially in Go 1.5, making it possible to
+	// see inside non-exported fields (which cannot be accessed with Interface()).
+	// Issue 8965.
+	{"%v", reflect.ValueOf(A{}).Field(0).String(), "<int Value>"}, // Equivalent to the old way.
+	{"%v", reflect.ValueOf(A{}).Field(0), "0"},                    // Sees inside the field.
+
+	// verbs apply to the extracted value too.
+	{"%s", reflect.ValueOf("hello"), "hello"},
+	{"%q", reflect.ValueOf("hello"), `"hello"`},
+	{"%#04x", reflect.ValueOf(256), "0x0100"},
+
+	// invalid reflect.Value doesn't crash.
+	{"%v", reflect.Value{}, "<invalid reflect.Value>"},
+	{"%v", &reflect.Value{}, "<invalid Value>"},
+	{"%v", SI{reflect.Value{}}, "{<invalid Value>}"},
+
+	// Tests to check that not supported verbs generate an error string.
+	{"%☠", nil, "%!☠(<nil>)"},
+	{"%☠", interface{}(nil), "%!☠(<nil>)"},
+	{"%☠", int(0), "%!☠(int=0)"},
+	{"%☠", uint(0), "%!☠(uint=0)"},
+	{"%☠", []byte{0, 1}, "[%!☠(uint8=0) %!☠(uint8=1)]"},
+	{"%☠", []uint8{0, 1}, "[%!☠(uint8=0) %!☠(uint8=1)]"},
+	{"%☠", [1]byte{0}, "[%!☠(uint8=0)]"},
+	{"%☠", [1]uint8{0}, "[%!☠(uint8=0)]"},
+	{"%☠", "hello", "%!☠(string=hello)"},
+	{"%☠", 1.2345678, "%!☠(float64=1.2345678)"},
+	{"%☠", float32(1.2345678), "%!☠(float32=1.2345678)"},
+	{"%☠", 1.2345678 + 1.2345678i, "%!☠(complex128=(1.2345678+1.2345678i))"},
+	{"%☠", complex64(1.2345678 + 1.2345678i), "%!☠(complex64=(1.2345678+1.2345678i))"},
+	{"%☠", &intVar, "%!☠(*int=0xPTR)"},
+	{"%☠", make(chan int), "%!☠(chan int=0xPTR)"},
+	{"%☠", func() {}, "%!☠(func()=0xPTR)"},
+	{"%☠", reflect.ValueOf(renamedInt(0)), "%!☠(fmt_test.renamedInt=0)"},
+	{"%☠", SI{renamedInt(0)}, "{%!☠(fmt_test.renamedInt=0)}"},
+	{"%☠", &[]interface{}{I(1), G(2)}, "&[%!☠(fmt_test.I=1) %!☠(fmt_test.G=2)]"},
+	{"%☠", SI{&[]interface{}{I(1), G(2)}}, "{%!☠(*[]interface {}=&[1 2])}"},
+	{"%☠", reflect.Value{}, "<invalid reflect.Value>"},
+	{"%☠", map[float64]int{NaN: 1}, "map[%!☠(float64=NaN):%!☠(<nil>)]"},
+}
+
+// zeroFill generates zero-filled strings of the specified width. The length
+// of the suffix (but not the prefix) is compensated for in the width calculation.
+func zeroFill(prefix string, width int, suffix string) string {
+	return prefix + strings.Repeat("0", width-len(suffix)) + suffix
+}
+
+func TestSprintf(t *testing.T) {
+	for _, tt := range fmtTests {
+		s := Sprintf(tt.fmt, tt.val)
+		i := strings.Index(tt.out, "PTR")
+		if i >= 0 && i < len(s) {
+			var pattern, chars string
+			switch {
+			case strings.HasPrefix(tt.out[i:], "PTR_b"):
+				pattern = "PTR_b"
+				chars = "01"
+			case strings.HasPrefix(tt.out[i:], "PTR_o"):
+				pattern = "PTR_o"
+				chars = "01234567"
+			case strings.HasPrefix(tt.out[i:], "PTR_d"):
+				pattern = "PTR_d"
+				chars = "0123456789"
+			case strings.HasPrefix(tt.out[i:], "PTR_x"):
+				pattern = "PTR_x"
+				chars = "0123456789abcdef"
+			case strings.HasPrefix(tt.out[i:], "PTR_X"):
+				pattern = "PTR_X"
+				chars = "0123456789ABCDEF"
+			default:
+				pattern = "PTR"
+				chars = "0123456789abcdefABCDEF"
+			}
+			p := s[:i] + pattern
+			for j := i; j < len(s); j++ {
+				if !strings.ContainsRune(chars, rune(s[j])) {
+					p += s[j:]
+					break
+				}
+			}
+			s = p
+		}
+		if s != tt.out {
+			if _, ok := tt.val.(string); ok {
+				// Don't requote the already-quoted strings.
+				// It's too confusing to read the errors.
+				t.Errorf("Sprintf(%q, %q) = <%s> want <%s>", tt.fmt, tt.val, s, tt.out)
+			} else {
+				t.Errorf("Sprintf(%q, %v) = %q want %q", tt.fmt, tt.val, s, tt.out)
+			}
+		}
+	}
+}
+
+// TestComplexFormatting checks that a complex always formats to the same
+// thing as if done by hand with two singleton prints.
+func TestComplexFormatting(t *testing.T) {
+	var yesNo = []bool{true, false}
+	var values = []float64{1, 0, -1, posInf, negInf, NaN}
+	for _, plus := range yesNo {
+		for _, zero := range yesNo {
+			for _, space := range yesNo {
+				for _, char := range "fFeEgG" {
+					realFmt := "%"
+					if zero {
+						realFmt += "0"
+					}
+					if space {
+						realFmt += " "
+					}
+					if plus {
+						realFmt += "+"
+					}
+					realFmt += "10.2"
+					realFmt += string(char)
+					// Imaginary part always has a sign, so force + and ignore space.
+					imagFmt := "%"
+					if zero {
+						imagFmt += "0"
+					}
+					imagFmt += "+"
+					imagFmt += "10.2"
+					imagFmt += string(char)
+					for _, realValue := range values {
+						for _, imagValue := range values {
+							one := Sprintf(realFmt, complex(realValue, imagValue))
+							two := Sprintf("("+realFmt+imagFmt+"i)", realValue, imagValue)
+							if one != two {
+								t.Error(f, one, two)
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
+type SE []interface{} // slice of empty; notational compactness.
+
+var reorderTests = []struct {
+	fmt string
+	val SE
+	out string
+}{
+	{"%[1]d", SE{1}, "1"},
+	{"%[2]d", SE{2, 1}, "1"},
+	{"%[2]d %[1]d", SE{1, 2}, "2 1"},
+	{"%[2]*[1]d", SE{2, 5}, "    2"},
+	{"%6.2f", SE{12.0}, " 12.00"}, // Explicit version of next line.
+	{"%[3]*.[2]*[1]f", SE{12.0, 2, 6}, " 12.00"},
+	{"%[1]*.[2]*[3]f", SE{6, 2, 12.0}, " 12.00"},
+	{"%10f", SE{12.0}, " 12.000000"},
+	{"%[1]*[3]f", SE{10, 99, 12.0}, " 12.000000"},
+	{"%.6f", SE{12.0}, "12.000000"}, // Explicit version of next line.
+	{"%.[1]*[3]f", SE{6, 99, 12.0}, "12.000000"},
+	{"%6.f", SE{12.0}, "    12"}, //  // Explicit version of next line; empty precision means zero.
+	{"%[1]*.[3]f", SE{6, 3, 12.0}, "    12"},
+	// An actual use! Print the same arguments twice.
+	{"%d %d %d %#[1]o %#o %#o", SE{11, 12, 13}, "11 12 13 013 014 015"},
+
+	// Erroneous cases.
+	{"%[d", SE{2, 1}, "%!d(BADINDEX)"},
+	{"%]d", SE{2, 1}, "%!](int=2)d%!(EXTRA int=1)"},
+	{"%[]d", SE{2, 1}, "%!d(BADINDEX)"},
+	{"%[-3]d", SE{2, 1}, "%!d(BADINDEX)"},
+	{"%[99]d", SE{2, 1}, "%!d(BADINDEX)"},
+	{"%[3]", SE{2, 1}, "%!(NOVERB)"},
+	{"%[1].2d", SE{5, 6}, "%!d(BADINDEX)"},
+	{"%[1]2d", SE{2, 1}, "%!d(BADINDEX)"},
+	{"%3.[2]d", SE{7}, "%!d(BADINDEX)"},
+	{"%.[2]d", SE{7}, "%!d(BADINDEX)"},
+	{"%d %d %d %#[1]o %#o %#o %#o", SE{11, 12, 13}, "11 12 13 013 014 015 %!o(MISSING)"},
+	{"%[5]d %[2]d %d", SE{1, 2, 3}, "%!d(BADINDEX) 2 3"},
+	{"%d %[3]d %d", SE{1, 2}, "1 %!d(BADINDEX) 2"}, // Erroneous index does not affect sequence.
+	{"%.[]", SE{}, "%!](BADINDEX)"},                // Issue 10675
+	{"%.-3d", SE{42}, "%!-(int=42)3d"},             // TODO: Should this set return better error messages?
+	{"%2147483648d", SE{42}, "%!(NOVERB)%!(EXTRA int=42)"},
+	{"%-2147483648d", SE{42}, "%!(NOVERB)%!(EXTRA int=42)"},
+	{"%.2147483648d", SE{42}, "%!(NOVERB)%!(EXTRA int=42)"},
+}
+
+func TestReorder(t *testing.T) {
+	for _, tt := range reorderTests {
+		s := Sprintf(tt.fmt, tt.val...)
+		if s != tt.out {
+			t.Errorf("Sprintf(%q, %v) = <%s> want <%s>", tt.fmt, tt.val, s, tt.out)
+		} else {
+		}
+	}
+}
+
+func BenchmarkSprintfPadding(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%16f", 1.0)
+		}
+	})
+}
+
+func BenchmarkSprintfEmpty(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("")
+		}
+	})
+}
+
+func BenchmarkSprintfString(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%s", "hello")
+		}
+	})
+}
+
+func BenchmarkSprintfTruncateString(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%.3s", "日本語日本語日本語")
+		}
+	})
+}
+
+func BenchmarkSprintfQuoteString(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%q", "日本語日本語日本語")
+		}
+	})
+}
+
+func BenchmarkSprintfInt(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%d", 5)
+		}
+	})
+}
+
+func BenchmarkSprintfIntInt(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%d %d", 5, 6)
+		}
+	})
+}
+
+func BenchmarkSprintfPrefixedInt(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("This is some meaningless prefix text that needs to be scanned %d", 6)
+		}
+	})
+}
+
+func BenchmarkSprintfFloat(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%g", 5.23184)
+		}
+	})
+}
+
+func BenchmarkSprintfComplex(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%f", 5.23184+5.23184i)
+		}
+	})
+}
+
+func BenchmarkSprintfBoolean(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%t", true)
+		}
+	})
+}
+
+func BenchmarkSprintfHexString(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("% #x", "0123456789abcdef")
+		}
+	})
+}
+
+func BenchmarkSprintfHexBytes(b *testing.B) {
+	data := []byte("0123456789abcdef")
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("% #x", data)
+		}
+	})
+}
+
+func BenchmarkSprintfBytes(b *testing.B) {
+	data := []byte("0123456789abcdef")
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%v", data)
+		}
+	})
+}
+
+func BenchmarkSprintfStringer(b *testing.B) {
+	stringer := I(12345)
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%v", stringer)
+		}
+	})
+}
+
+func BenchmarkSprintfStructure(b *testing.B) {
+	s := &[]interface{}{SI{12345}, map[int]string{0: "hello"}}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%#v", s)
+		}
+	})
+}
+
+func BenchmarkManyArgs(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		var buf bytes.Buffer
+		for pb.Next() {
+			buf.Reset()
+			Fprintf(&buf, "%2d/%2d/%2d %d:%d:%d %s %s\n", 3, 4, 5, 11, 12, 13, "hello", "world")
+		}
+	})
+}
+
+func BenchmarkFprintInt(b *testing.B) {
+	var buf bytes.Buffer
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Fprint(&buf, 123456)
+	}
+}
+
+func BenchmarkFprintfBytes(b *testing.B) {
+	data := []byte(string("0123456789"))
+	var buf bytes.Buffer
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Fprintf(&buf, "%s", data)
+	}
+}
+
+func BenchmarkFprintIntNoAlloc(b *testing.B) {
+	var x interface{} = 123456
+	var buf bytes.Buffer
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Fprint(&buf, x)
+	}
+}
+
+var mallocBuf bytes.Buffer
+var mallocPointer *int // A pointer so we know the interface value won't allocate.
+
+var mallocTest = []struct {
+	count int
+	desc  string
+	fn    func()
+}{
+	{0, `Sprintf("")`, func() { Sprintf("") }},
+	{1, `Sprintf("xxx")`, func() { Sprintf("xxx") }},
+	{2, `Sprintf("%x")`, func() { Sprintf("%x", 7) }},
+	{2, `Sprintf("%s")`, func() { Sprintf("%s", "hello") }},
+	{3, `Sprintf("%x %x")`, func() { Sprintf("%x %x", 7, 112) }},
+	{2, `Sprintf("%g")`, func() { Sprintf("%g", float32(3.14159)) }}, // TODO: Can this be 1?
+	{1, `Fprintf(buf, "%s")`, func() { mallocBuf.Reset(); Fprintf(&mallocBuf, "%s", "hello") }},
+	// If the interface value doesn't need to allocate, amortized allocation overhead should be zero.
+	{0, `Fprintf(buf, "%x %x %x")`, func() {
+		mallocBuf.Reset()
+		Fprintf(&mallocBuf, "%x %x %x", mallocPointer, mallocPointer, mallocPointer)
+	}},
+}
+
+var _ bytes.Buffer
+
+func TestCountMallocs(t *testing.T) {
+	switch {
+	case testing.Short():
+		t.Skip("skipping malloc count in short mode")
+	case runtime.GOMAXPROCS(0) > 1:
+		t.Skip("skipping; GOMAXPROCS>1")
+	case race.Enabled:
+		t.Skip("skipping malloc count under race detector")
+	}
+	for _, mt := range mallocTest {
+		mallocs := testing.AllocsPerRun(100, mt.fn)
+		if got, max := mallocs, float64(mt.count); got > max {
+			t.Errorf("%s: got %v allocs, want <=%v", mt.desc, got, max)
+		}
+	}
+}
+
+type flagPrinter struct{}
+
+func (flagPrinter) Format(f State, c rune) {
+	s := "%"
+	for i := 0; i < 128; i++ {
+		if f.Flag(i) {
+			s += string(i)
+		}
+	}
+	if w, ok := f.Width(); ok {
+		s += Sprintf("%d", w)
+	}
+	if p, ok := f.Precision(); ok {
+		s += Sprintf(".%d", p)
+	}
+	s += string(c)
+	io.WriteString(f, "["+s+"]")
+}
+
+var flagtests = []struct {
+	in  string
+	out string
+}{
+	{"%a", "[%a]"},
+	{"%-a", "[%-a]"},
+	{"%+a", "[%+a]"},
+	{"%#a", "[%#a]"},
+	{"% a", "[% a]"},
+	{"%0a", "[%0a]"},
+	{"%1.2a", "[%1.2a]"},
+	{"%-1.2a", "[%-1.2a]"},
+	{"%+1.2a", "[%+1.2a]"},
+	{"%-+1.2a", "[%+-1.2a]"},
+	{"%-+1.2abc", "[%+-1.2a]bc"},
+	{"%-1.2abc", "[%-1.2a]bc"},
+}
+
+func TestFlagParser(t *testing.T) {
+	var flagprinter flagPrinter
+	for _, tt := range flagtests {
+		s := Sprintf(tt.in, &flagprinter)
+		if s != tt.out {
+			t.Errorf("Sprintf(%q, &flagprinter) => %q, want %q", tt.in, s, tt.out)
+		}
+	}
+}
+
+func TestStructPrinter(t *testing.T) {
+	type T struct {
+		a string
+		b string
+		c int
+	}
+	var s T
+	s.a = "abc"
+	s.b = "def"
+	s.c = 123
+	var tests = []struct {
+		fmt string
+		out string
+	}{
+		{"%v", "{abc def 123}"},
+		{"%+v", "{a:abc b:def c:123}"},
+		{"%#v", `fmt_test.T{a:"abc", b:"def", c:123}`},
+	}
+	for _, tt := range tests {
+		out := Sprintf(tt.fmt, s)
+		if out != tt.out {
+			t.Errorf("Sprintf(%q, s) = %#q, want %#q", tt.fmt, out, tt.out)
+		}
+		// The same but with a pointer.
+		out = Sprintf(tt.fmt, &s)
+		if out != "&"+tt.out {
+			t.Errorf("Sprintf(%q, &s) = %#q, want %#q", tt.fmt, out, "&"+tt.out)
+		}
+	}
+}
+
+func TestSlicePrinter(t *testing.T) {
+	slice := []int{}
+	s := Sprint(slice)
+	if s != "[]" {
+		t.Errorf("empty slice printed as %q not %q", s, "[]")
+	}
+	slice = []int{1, 2, 3}
+	s = Sprint(slice)
+	if s != "[1 2 3]" {
+		t.Errorf("slice: got %q expected %q", s, "[1 2 3]")
+	}
+	s = Sprint(&slice)
+	if s != "&[1 2 3]" {
+		t.Errorf("&slice: got %q expected %q", s, "&[1 2 3]")
+	}
+}
+
+// presentInMap checks map printing using substrings so we don't depend on the
+// print order.
+func presentInMap(s string, a []string, t *testing.T) {
+	for i := 0; i < len(a); i++ {
+		loc := strings.Index(s, a[i])
+		if loc < 0 {
+			t.Errorf("map print: expected to find %q in %q", a[i], s)
+		}
+		// make sure the match ends here
+		loc += len(a[i])
+		if loc >= len(s) || (s[loc] != ' ' && s[loc] != ']') {
+			t.Errorf("map print: %q not properly terminated in %q", a[i], s)
+		}
+	}
+}
+
+func TestMapPrinter(t *testing.T) {
+	m0 := make(map[int]string)
+	s := Sprint(m0)
+	if s != "map[]" {
+		t.Errorf("empty map printed as %q not %q", s, "map[]")
+	}
+	m1 := map[int]string{1: "one", 2: "two", 3: "three"}
+	a := []string{"1:one", "2:two", "3:three"}
+	presentInMap(Sprintf("%v", m1), a, t)
+	presentInMap(Sprint(m1), a, t)
+	// Pointer to map prints the same but with initial &.
+	if !strings.HasPrefix(Sprint(&m1), "&") {
+		t.Errorf("no initial & for address of map")
+	}
+	presentInMap(Sprintf("%v", &m1), a, t)
+	presentInMap(Sprint(&m1), a, t)
+}
+
+func TestEmptyMap(t *testing.T) {
+	const emptyMapStr = "map[]"
+	var m map[string]int
+	s := Sprint(m)
+	if s != emptyMapStr {
+		t.Errorf("nil map printed as %q not %q", s, emptyMapStr)
+	}
+	m = make(map[string]int)
+	s = Sprint(m)
+	if s != emptyMapStr {
+		t.Errorf("empty map printed as %q not %q", s, emptyMapStr)
+	}
+}
+
+// TestBlank checks that Sprint (and hence Print, Fprint) puts spaces in the
+// right places, that is, between arg pairs in which neither is a string.
+func TestBlank(t *testing.T) {
+	got := Sprint("<", 1, ">:", 1, 2, 3, "!")
+	expect := "<1>:1 2 3!"
+	if got != expect {
+		t.Errorf("got %q expected %q", got, expect)
+	}
+}
+
+// TestBlankln checks that Sprintln (and hence Println, Fprintln) puts spaces in
+// the right places, that is, between all arg pairs.
+func TestBlankln(t *testing.T) {
+	got := Sprintln("<", 1, ">:", 1, 2, 3, "!")
+	expect := "< 1 >: 1 2 3 !\n"
+	if got != expect {
+		t.Errorf("got %q expected %q", got, expect)
+	}
+}
+
+// TestFormatterPrintln checks Formatter with Sprint, Sprintln, Sprintf.
+func TestFormatterPrintln(t *testing.T) {
+	f := F(1)
+	expect := "<v=F(1)>\n"
+	s := Sprint(f, "\n")
+	if s != expect {
+		t.Errorf("Sprint wrong with Formatter: expected %q got %q", expect, s)
+	}
+	s = Sprintln(f)
+	if s != expect {
+		t.Errorf("Sprintln wrong with Formatter: expected %q got %q", expect, s)
+	}
+	s = Sprintf("%v\n", f)
+	if s != expect {
+		t.Errorf("Sprintf wrong with Formatter: expected %q got %q", expect, s)
+	}
+}
+
+func args(a ...interface{}) []interface{} { return a }
+
+var startests = []struct {
+	fmt string
+	in  []interface{}
+	out string
+}{
+	{"%*d", args(4, 42), "  42"},
+	{"%-*d", args(4, 42), "42  "},
+	{"%*d", args(-4, 42), "42  "},
+	{"%-*d", args(-4, 42), "42  "},
+	{"%.*d", args(4, 42), "0042"},
+	{"%*.*d", args(8, 4, 42), "    0042"},
+	{"%0*d", args(4, 42), "0042"},
+	// Some non-int types for width. (Issue 10732).
+	{"%0*d", args(uint(4), 42), "0042"},
+	{"%0*d", args(uint64(4), 42), "0042"},
+	{"%0*d", args('\x04', 42), "0042"},
+	{"%0*d", args(uintptr(4), 42), "0042"},
+
+	// erroneous
+	{"%*d", args(nil, 42), "%!(BADWIDTH)42"},
+	{"%*d", args(int(1e7), 42), "%!(BADWIDTH)42"},
+	{"%*d", args(int(-1e7), 42), "%!(BADWIDTH)42"},
+	{"%.*d", args(nil, 42), "%!(BADPREC)42"},
+	{"%.*d", args(-1, 42), "%!(BADPREC)42"},
+	{"%.*d", args(int(1e7), 42), "%!(BADPREC)42"},
+	{"%.*d", args(uint(1e7), 42), "%!(BADPREC)42"},
+	{"%.*d", args(uint64(1<<63), 42), "%!(BADPREC)42"},   // Huge negative (-inf).
+	{"%.*d", args(uint64(1<<64-1), 42), "%!(BADPREC)42"}, // Small negative (-1).
+	{"%*d", args(5, "foo"), "%!d(string=  foo)"},
+	{"%*% %d", args(20, 5), "% 5"},
+	{"%*", args(4), "%!(NOVERB)"},
+}
+
+func TestWidthAndPrecision(t *testing.T) {
+	for i, tt := range startests {
+		s := Sprintf(tt.fmt, tt.in...)
+		if s != tt.out {
+			t.Errorf("#%d: %q: got %q expected %q", i, tt.fmt, s, tt.out)
+		}
+	}
+}
+
+// PanicS is a type that panics in String.
+type PanicS struct {
+	message interface{}
+}
+
+// Value receiver.
+func (p PanicS) String() string {
+	panic(p.message)
+}
+
+// PanicGo is a type that panics in GoString.
+type PanicGo struct {
+	message interface{}
+}
+
+// Value receiver.
+func (p PanicGo) GoString() string {
+	panic(p.message)
+}
+
+// PanicF is a type that panics in Format.
+type PanicF struct {
+	message interface{}
+}
+
+// Value receiver.
+func (p PanicF) Format(f State, c rune) {
+	panic(p.message)
+}
+
+var panictests = []struct {
+	fmt string
+	in  interface{}
+	out string
+}{
+	// String
+	{"%s", (*PanicS)(nil), "<nil>"}, // nil pointer special case
+	{"%s", PanicS{io.ErrUnexpectedEOF}, "%!s(PANIC=unexpected EOF)"},
+	{"%s", PanicS{3}, "%!s(PANIC=3)"},
+	// GoString
+	{"%#v", (*PanicGo)(nil), "<nil>"}, // nil pointer special case
+	{"%#v", PanicGo{io.ErrUnexpectedEOF}, "%!v(PANIC=unexpected EOF)"},
+	{"%#v", PanicGo{3}, "%!v(PANIC=3)"},
+	// Issue 18282. catchPanic should not clear fmtFlags permanently.
+	{"%#v", []interface{}{PanicGo{3}, PanicGo{3}}, "[]interface {}{%!v(PANIC=3), %!v(PANIC=3)}"},
+	// Format
+	{"%s", (*PanicF)(nil), "<nil>"}, // nil pointer special case
+	{"%s", PanicF{io.ErrUnexpectedEOF}, "%!s(PANIC=unexpected EOF)"},
+	{"%s", PanicF{3}, "%!s(PANIC=3)"},
+}
+
+func TestPanics(t *testing.T) {
+	for i, tt := range panictests {
+		s := Sprintf(tt.fmt, tt.in)
+		if s != tt.out {
+			t.Errorf("%d: %q: got %q expected %q", i, tt.fmt, s, tt.out)
+		}
+	}
+}
+
+// recurCount tests that erroneous String routine doesn't cause fatal recursion.
+var recurCount = 0
+
+type Recur struct {
+	i      int
+	failed *bool
+}
+
+func (r *Recur) String() string {
+	if recurCount++; recurCount > 10 {
+		*r.failed = true
+		return "FAIL"
+	}
+	// This will call badVerb. Before the fix, that would cause us to recur into
+	// this routine to print %!p(value). Now we don't call the user's method
+	// during an error.
+	return Sprintf("recur@%p value: %d", r, r.i)
+}
+
+func TestBadVerbRecursion(t *testing.T) {
+	failed := false
+	r := &Recur{3, &failed}
+	Sprintf("recur@%p value: %d\n", &r, r.i)
+	if failed {
+		t.Error("fail with pointer")
+	}
+	failed = false
+	r = &Recur{4, &failed}
+	Sprintf("recur@%p, value: %d\n", r, r.i)
+	if failed {
+		t.Error("fail with value")
+	}
+}
+
+func TestIsSpace(t *testing.T) {
+	// This tests the internal isSpace function.
+	// IsSpace = isSpace is defined in export_test.go.
+	for i := rune(0); i <= unicode.MaxRune; i++ {
+		if IsSpace(i) != unicode.IsSpace(i) {
+			t.Errorf("isSpace(%U) = %v, want %v", i, IsSpace(i), unicode.IsSpace(i))
+		}
+	}
+}
+
+func TestNilDoesNotBecomeTyped(t *testing.T) {
+	type A struct{}
+	type B struct{}
+	var a *A = nil
+	var b B = B{}
+	got := Sprintf("%s %s %s %s %s", nil, a, nil, b, nil) // go vet should complain about this line.
+	const expect = "%!s(<nil>) %!s(*fmt_test.A=<nil>) %!s(<nil>) {} %!s(<nil>)"
+	if got != expect {
+		t.Errorf("expected:\n\t%q\ngot:\n\t%q", expect, got)
+	}
+}
+
+var formatterFlagTests = []struct {
+	in  string
+	val interface{}
+	out string
+}{
+	// scalar values with the (unused by fmt) 'a' verb.
+	{"%a", flagPrinter{}, "[%a]"},
+	{"%-a", flagPrinter{}, "[%-a]"},
+	{"%+a", flagPrinter{}, "[%+a]"},
+	{"%#a", flagPrinter{}, "[%#a]"},
+	{"% a", flagPrinter{}, "[% a]"},
+	{"%0a", flagPrinter{}, "[%0a]"},
+	{"%1.2a", flagPrinter{}, "[%1.2a]"},
+	{"%-1.2a", flagPrinter{}, "[%-1.2a]"},
+	{"%+1.2a", flagPrinter{}, "[%+1.2a]"},
+	{"%-+1.2a", flagPrinter{}, "[%+-1.2a]"},
+	{"%-+1.2abc", flagPrinter{}, "[%+-1.2a]bc"},
+	{"%-1.2abc", flagPrinter{}, "[%-1.2a]bc"},
+
+	// composite values with the 'a' verb
+	{"%a", [1]flagPrinter{}, "[[%a]]"},
+	{"%-a", [1]flagPrinter{}, "[[%-a]]"},
+	{"%+a", [1]flagPrinter{}, "[[%+a]]"},
+	{"%#a", [1]flagPrinter{}, "[[%#a]]"},
+	{"% a", [1]flagPrinter{}, "[[% a]]"},
+	{"%0a", [1]flagPrinter{}, "[[%0a]]"},
+	{"%1.2a", [1]flagPrinter{}, "[[%1.2a]]"},
+	{"%-1.2a", [1]flagPrinter{}, "[[%-1.2a]]"},
+	{"%+1.2a", [1]flagPrinter{}, "[[%+1.2a]]"},
+	{"%-+1.2a", [1]flagPrinter{}, "[[%+-1.2a]]"},
+	{"%-+1.2abc", [1]flagPrinter{}, "[[%+-1.2a]]bc"},
+	{"%-1.2abc", [1]flagPrinter{}, "[[%-1.2a]]bc"},
+
+	// simple values with the 'v' verb
+	{"%v", flagPrinter{}, "[%v]"},
+	{"%-v", flagPrinter{}, "[%-v]"},
+	{"%+v", flagPrinter{}, "[%+v]"},
+	{"%#v", flagPrinter{}, "[%#v]"},
+	{"% v", flagPrinter{}, "[% v]"},
+	{"%0v", flagPrinter{}, "[%0v]"},
+	{"%1.2v", flagPrinter{}, "[%1.2v]"},
+	{"%-1.2v", flagPrinter{}, "[%-1.2v]"},
+	{"%+1.2v", flagPrinter{}, "[%+1.2v]"},
+	{"%-+1.2v", flagPrinter{}, "[%+-1.2v]"},
+	{"%-+1.2vbc", flagPrinter{}, "[%+-1.2v]bc"},
+	{"%-1.2vbc", flagPrinter{}, "[%-1.2v]bc"},
+
+	// composite values with the 'v' verb.
+	{"%v", [1]flagPrinter{}, "[[%v]]"},
+	{"%-v", [1]flagPrinter{}, "[[%-v]]"},
+	{"%+v", [1]flagPrinter{}, "[[%+v]]"},
+	{"%#v", [1]flagPrinter{}, "[1]fmt_test.flagPrinter{[%#v]}"},
+	{"% v", [1]flagPrinter{}, "[[% v]]"},
+	{"%0v", [1]flagPrinter{}, "[[%0v]]"},
+	{"%1.2v", [1]flagPrinter{}, "[[%1.2v]]"},
+	{"%-1.2v", [1]flagPrinter{}, "[[%-1.2v]]"},
+	{"%+1.2v", [1]flagPrinter{}, "[[%+1.2v]]"},
+	{"%-+1.2v", [1]flagPrinter{}, "[[%+-1.2v]]"},
+	{"%-+1.2vbc", [1]flagPrinter{}, "[[%+-1.2v]]bc"},
+	{"%-1.2vbc", [1]flagPrinter{}, "[[%-1.2v]]bc"},
+}
+
+func TestFormatterFlags(t *testing.T) {
+	for _, tt := range formatterFlagTests {
+		s := Sprintf(tt.in, tt.val)
+		if s != tt.out {
+			t.Errorf("Sprintf(%q, %T) = %q, want %q", tt.in, tt.val, s, tt.out)
+		}
+	}
+}
+
+func TestParsenum(t *testing.T) {
+	testCases := []struct {
+		s          string
+		start, end int
+		num        int
+		isnum      bool
+		newi       int
+	}{
+		{"a123", 0, 4, 0, false, 0},
+		{"1234", 1, 1, 0, false, 1},
+		{"123a", 0, 4, 123, true, 3},
+		{"12a3", 0, 4, 12, true, 2},
+		{"1234", 0, 4, 1234, true, 4},
+		{"1a234", 1, 3, 0, false, 1},
+	}
+	for _, tt := range testCases {
+		num, isnum, newi := Parsenum(tt.s, tt.start, tt.end)
+		if num != tt.num || isnum != tt.isnum || newi != tt.newi {
+			t.Errorf("parsenum(%q, %d, %d) = %d, %v, %d, want %d, %v, %d", tt.s, tt.start, tt.end, num, isnum, newi, tt.num, tt.isnum, tt.newi)
+		}
+	}
+}
diff --git a/message/format.go b/message/format.go
new file mode 100644
index 0000000..f80082b
--- /dev/null
+++ b/message/format.go
@@ -0,0 +1,539 @@
+// +build ignore
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fmt
+
+import (
+	"strconv"
+	"unicode/utf8"
+)
+
+const (
+	ldigits = "0123456789abcdefx"
+	udigits = "0123456789ABCDEFX"
+)
+
+const (
+	signed   = true
+	unsigned = false
+)
+
+// flags placed in a separate struct for easy clearing.
+type fmtFlags struct {
+	widPresent  bool
+	precPresent bool
+	minus       bool
+	plus        bool
+	sharp       bool
+	space       bool
+	zero        bool
+
+	// For the formats %+v %#v, we set the plusV/sharpV flags
+	// and clear the plus/sharp flags since %+v and %#v are in effect
+	// different, flagless formats set at the top level.
+	plusV  bool
+	sharpV bool
+}
+
+// A fmt is the raw formatter used by Printf etc.
+// It prints into a buffer that must be set up separately.
+type fmt struct {
+	buf *buffer
+
+	fmtFlags
+
+	wid  int // width
+	prec int // precision
+
+	// intbuf is large enough to store %b of an int64 with a sign and
+	// avoids padding at the end of the struct on 32 bit architectures.
+	intbuf [68]byte
+}
+
+func (f *fmt) clearflags() {
+	f.fmtFlags = fmtFlags{}
+}
+
+func (f *fmt) init(buf *buffer) {
+	f.buf = buf
+	f.clearflags()
+}
+
+// writePadding generates n bytes of padding.
+func (f *fmt) writePadding(n int) {
+	if n <= 0 { // No padding bytes needed.
+		return
+	}
+	buf := *f.buf
+	oldLen := len(buf)
+	newLen := oldLen + n
+	// Make enough room for padding.
+	if newLen > cap(buf) {
+		buf = make(buffer, cap(buf)*2+n)
+		copy(buf, *f.buf)
+	}
+	// Decide which byte the padding should be filled with.
+	padByte := byte(' ')
+	if f.zero {
+		padByte = byte('0')
+	}
+	// Fill padding with padByte.
+	padding := buf[oldLen:newLen]
+	for i := range padding {
+		padding[i] = padByte
+	}
+	*f.buf = buf[:newLen]
+}
+
+// pad appends b to f.buf, padded on left (!f.minus) or right (f.minus).
+func (f *fmt) pad(b []byte) {
+	if !f.widPresent || f.wid == 0 {
+		f.buf.Write(b)
+		return
+	}
+	width := f.wid - utf8.RuneCount(b)
+	if !f.minus {
+		// left padding
+		f.writePadding(width)
+		f.buf.Write(b)
+	} else {
+		// right padding
+		f.buf.Write(b)
+		f.writePadding(width)
+	}
+}
+
+// padString appends s to f.buf, padded on left (!f.minus) or right (f.minus).
+func (f *fmt) padString(s string) {
+	if !f.widPresent || f.wid == 0 {
+		f.buf.WriteString(s)
+		return
+	}
+	width := f.wid - utf8.RuneCountInString(s)
+	if !f.minus {
+		// left padding
+		f.writePadding(width)
+		f.buf.WriteString(s)
+	} else {
+		// right padding
+		f.buf.WriteString(s)
+		f.writePadding(width)
+	}
+}
+
+// fmt_boolean formats a boolean.
+func (f *fmt) fmt_boolean(v bool) {
+	if v {
+		f.padString("true")
+	} else {
+		f.padString("false")
+	}
+}
+
+// fmt_unicode formats a uint64 as "U+0078" or with f.sharp set as "U+0078 'x'".
+func (f *fmt) fmt_unicode(u uint64) {
+	buf := f.intbuf[0:]
+
+	// With default precision set the maximum needed buf length is 18
+	// for formatting -1 with %#U ("U+FFFFFFFFFFFFFFFF") which fits
+	// into the already allocated intbuf with a capacity of 68 bytes.
+	prec := 4
+	if f.precPresent && f.prec > 4 {
+		prec = f.prec
+		// Compute space needed for "U+" , number, " '", character, "'".
+		width := 2 + prec + 2 + utf8.UTFMax + 1
+		if width > len(buf) {
+			buf = make([]byte, width)
+		}
+	}
+
+	// Format into buf, ending at buf[i]. Formatting numbers is easier right-to-left.
+	i := len(buf)
+
+	// For %#U we want to add a space and a quoted character at the end of the buffer.
+	if f.sharp && u <= utf8.MaxRune && strconv.IsPrint(rune(u)) {
+		i--
+		buf[i] = '\''
+		i -= utf8.RuneLen(rune(u))
+		utf8.EncodeRune(buf[i:], rune(u))
+		i--
+		buf[i] = '\''
+		i--
+		buf[i] = ' '
+	}
+	// Format the Unicode code point u as a hexadecimal number.
+	for u >= 16 {
+		i--
+		buf[i] = udigits[u&0xF]
+		prec--
+		u >>= 4
+	}
+	i--
+	buf[i] = udigits[u]
+	prec--
+	// Add zeros in front of the number until requested precision is reached.
+	for prec > 0 {
+		i--
+		buf[i] = '0'
+		prec--
+	}
+	// Add a leading "U+".
+	i--
+	buf[i] = '+'
+	i--
+	buf[i] = 'U'
+
+	oldZero := f.zero
+	f.zero = false
+	f.pad(buf[i:])
+	f.zero = oldZero
+}
+
+// fmt_integer formats signed and unsigned integers.
+func (f *fmt) fmt_integer(u uint64, base int, isSigned bool, digits string) {
+	negative := isSigned && int64(u) < 0
+	if negative {
+		u = -u
+	}
+
+	buf := f.intbuf[0:]
+	// The already allocated f.intbuf with a capacity of 68 bytes
+	// is large enough for integer formatting when no precision or width is set.
+	if f.widPresent || f.precPresent {
+		// Account 3 extra bytes for possible addition of a sign and "0x".
+		width := 3 + f.wid + f.prec // wid and prec are always positive.
+		if width > len(buf) {
+			// We're going to need a bigger boat.
+			buf = make([]byte, width)
+		}
+	}
+
+	// Two ways to ask for extra leading zero digits: %.3d or %03d.
+	// If both are specified the f.zero flag is ignored and
+	// padding with spaces is used instead.
+	prec := 0
+	if f.precPresent {
+		prec = f.prec
+		// Precision of 0 and value of 0 means "print nothing" but padding.
+		if prec == 0 && u == 0 {
+			oldZero := f.zero
+			f.zero = false
+			f.writePadding(f.wid)
+			f.zero = oldZero
+			return
+		}
+	} else if f.zero && f.widPresent {
+		prec = f.wid
+		if negative || f.plus || f.space {
+			prec-- // leave room for sign
+		}
+	}
+
+	// Because printing is easier right-to-left: format u into buf, ending at buf[i].
+	// We could make things marginally faster by splitting the 32-bit case out
+	// into a separate block but it's not worth the duplication, so u has 64 bits.
+	i := len(buf)
+	// Use constants for the division and modulo for more efficient code.
+	// Switch cases ordered by popularity.
+	switch base {
+	case 10:
+		for u >= 10 {
+			i--
+			next := u / 10
+			buf[i] = byte('0' + u - next*10)
+			u = next
+		}
+	case 16:
+		for u >= 16 {
+			i--
+			buf[i] = digits[u&0xF]
+			u >>= 4
+		}
+	case 8:
+		for u >= 8 {
+			i--
+			buf[i] = byte('0' + u&7)
+			u >>= 3
+		}
+	case 2:
+		for u >= 2 {
+			i--
+			buf[i] = byte('0' + u&1)
+			u >>= 1
+		}
+	default:
+		panic("fmt: unknown base; can't happen")
+	}
+	i--
+	buf[i] = digits[u]
+	for i > 0 && prec > len(buf)-i {
+		i--
+		buf[i] = '0'
+	}
+
+	// Various prefixes: 0x, -, etc.
+	if f.sharp {
+		switch base {
+		case 8:
+			if buf[i] != '0' {
+				i--
+				buf[i] = '0'
+			}
+		case 16:
+			// Add a leading 0x or 0X.
+			i--
+			buf[i] = digits[16]
+			i--
+			buf[i] = '0'
+		}
+	}
+
+	if negative {
+		i--
+		buf[i] = '-'
+	} else if f.plus {
+		i--
+		buf[i] = '+'
+	} else if f.space {
+		i--
+		buf[i] = ' '
+	}
+
+	// Left padding with zeros has already been handled like precision earlier
+	// or the f.zero flag is ignored due to an explicitly set precision.
+	oldZero := f.zero
+	f.zero = false
+	f.pad(buf[i:])
+	f.zero = oldZero
+}
+
+// truncate truncates the string to the specified precision, if present.
+func (f *fmt) truncate(s string) string {
+	if f.precPresent {
+		n := f.prec
+		for i := range s {
+			n--
+			if n < 0 {
+				return s[:i]
+			}
+		}
+	}
+	return s
+}
+
+// fmt_s formats a string.
+func (f *fmt) fmt_s(s string) {
+	s = f.truncate(s)
+	f.padString(s)
+}
+
+// fmt_sbx formats a string or byte slice as a hexadecimal encoding of its bytes.
+func (f *fmt) fmt_sbx(s string, b []byte, digits string) {
+	length := len(b)
+	if b == nil {
+		// No byte slice present. Assume string s should be encoded.
+		length = len(s)
+	}
+	// Set length to not process more bytes than the precision demands.
+	if f.precPresent && f.prec < length {
+		length = f.prec
+	}
+	// Compute width of the encoding taking into account the f.sharp and f.space flag.
+	width := 2 * length
+	if width > 0 {
+		if f.space {
+			// Each element encoded by two hexadecimals will get a leading 0x or 0X.
+			if f.sharp {
+				width *= 2
+			}
+			// Elements will be separated by a space.
+			width += length - 1
+		} else if f.sharp {
+			// Only a leading 0x or 0X will be added for the whole string.
+			width += 2
+		}
+	} else { // The byte slice or string that should be encoded is empty.
+		if f.widPresent {
+			f.writePadding(f.wid)
+		}
+		return
+	}
+	// Handle padding to the left.
+	if f.widPresent && f.wid > width && !f.minus {
+		f.writePadding(f.wid - width)
+	}
+	// Write the encoding directly into the output buffer.
+	buf := *f.buf
+	if f.sharp {
+		// Add leading 0x or 0X.
+		buf = append(buf, '0', digits[16])
+	}
+	var c byte
+	for i := 0; i < length; i++ {
+		if f.space && i > 0 {
+			// Separate elements with a space.
+			buf = append(buf, ' ')
+			if f.sharp {
+				// Add leading 0x or 0X for each element.
+				buf = append(buf, '0', digits[16])
+			}
+		}
+		if b != nil {
+			c = b[i] // Take a byte from the input byte slice.
+		} else {
+			c = s[i] // Take a byte from the input string.
+		}
+		// Encode each byte as two hexadecimal digits.
+		buf = append(buf, digits[c>>4], digits[c&0xF])
+	}
+	*f.buf = buf
+	// Handle padding to the right.
+	if f.widPresent && f.wid > width && f.minus {
+		f.writePadding(f.wid - width)
+	}
+}
+
+// fmt_sx formats a string as a hexadecimal encoding of its bytes.
+func (f *fmt) fmt_sx(s, digits string) {
+	f.fmt_sbx(s, nil, digits)
+}
+
+// fmt_bx formats a byte slice as a hexadecimal encoding of its bytes.
+func (f *fmt) fmt_bx(b []byte, digits string) {
+	f.fmt_sbx("", b, digits)
+}
+
+// fmt_q formats a string as a double-quoted, escaped Go string constant.
+// If f.sharp is set a raw (backquoted) string may be returned instead
+// if the string does not contain any control characters other than tab.
+func (f *fmt) fmt_q(s string) {
+	s = f.truncate(s)
+	if f.sharp && strconv.CanBackquote(s) {
+		f.padString("`" + s + "`")
+		return
+	}
+	buf := f.intbuf[:0]
+	if f.plus {
+		f.pad(strconv.AppendQuoteToASCII(buf, s))
+	} else {
+		f.pad(strconv.AppendQuote(buf, s))
+	}
+}
+
+// fmt_c formats an integer as a Unicode character.
+// If the character is not valid Unicode, it will print '\ufffd'.
+func (f *fmt) fmt_c(c uint64) {
+	r := rune(c)
+	if c > utf8.MaxRune {
+		r = utf8.RuneError
+	}
+	buf := f.intbuf[:0]
+	w := utf8.EncodeRune(buf[:utf8.UTFMax], r)
+	f.pad(buf[:w])
+}
+
+// fmt_qc formats an integer as a single-quoted, escaped Go character constant.
+// If the character is not valid Unicode, it will print '\ufffd'.
+func (f *fmt) fmt_qc(c uint64) {
+	r := rune(c)
+	if c > utf8.MaxRune {
+		r = utf8.RuneError
+	}
+	buf := f.intbuf[:0]
+	if f.plus {
+		f.pad(strconv.AppendQuoteRuneToASCII(buf, r))
+	} else {
+		f.pad(strconv.AppendQuoteRune(buf, r))
+	}
+}
+
+// fmt_float formats a float64. It assumes that verb is a valid format specifier
+// for strconv.AppendFloat and therefore fits into a byte.
+func (f *fmt) fmt_float(v float64, size int, verb rune, prec int) {
+	// Explicit precision in format specifier overrules default precision.
+	if f.precPresent {
+		prec = f.prec
+	}
+	// Format number, reserving space for leading + sign if needed.
+	num := strconv.AppendFloat(f.intbuf[:1], v, byte(verb), prec, size)
+	if num[1] == '-' || num[1] == '+' {
+		num = num[1:]
+	} else {
+		num[0] = '+'
+	}
+	// f.space means to add a leading space instead of a "+" sign unless
+	// the sign is explicitly asked for by f.plus.
+	if f.space && num[0] == '+' && !f.plus {
+		num[0] = ' '
+	}
+	// Special handling for infinities and NaN,
+	// which don't look like a number so shouldn't be padded with zeros.
+	if num[1] == 'I' || num[1] == 'N' {
+		oldZero := f.zero
+		f.zero = false
+		// Remove sign before NaN if not asked for.
+		if num[1] == 'N' && !f.space && !f.plus {
+			num = num[1:]
+		}
+		f.pad(num)
+		f.zero = oldZero
+		return
+	}
+	// The sharp flag forces printing a decimal point for non-binary formats
+	// and retains trailing zeros, which we may need to restore.
+	if f.sharp && verb != 'b' {
+		digits := 0
+		switch verb {
+		case 'v', 'g', 'G':
+			digits = prec
+			// If no precision is set explicitly use a precision of 6.
+			if digits == -1 {
+				digits = 6
+			}
+		}
+
+		// Buffer pre-allocated with enough room for
+		// exponent notations of the form "e+123".
+		var tailBuf [5]byte
+		tail := tailBuf[:0]
+
+		hasDecimalPoint := false
+		// Starting from i = 1 to skip sign at num[0].
+		for i := 1; i < len(num); i++ {
+			switch num[i] {
+			case '.':
+				hasDecimalPoint = true
+			case 'e', 'E':
+				tail = append(tail, num[i:]...)
+				num = num[:i]
+			default:
+				digits--
+			}
+		}
+		if !hasDecimalPoint {
+			num = append(num, '.')
+		}
+		for digits > 0 {
+			num = append(num, '0')
+			digits--
+		}
+		num = append(num, tail...)
+	}
+	// We want a sign if asked for and if the sign is not positive.
+	if f.plus || num[0] != '+' {
+		// If we're zero padding to the left we want the sign before the leading zeros.
+		// Achieve this by writing the sign out and then padding the unsigned number.
+		if f.zero && f.widPresent && f.wid > len(num) {
+			f.buf.WriteByte(num[0])
+			f.writePadding(f.wid - len(num))
+			f.buf.Write(num[1:])
+			return
+		}
+		f.pad(num)
+		return
+	}
+	// No sign to show and the number is positive; just print the unsigned number.
+	f.pad(num[1:])
+}
diff --git a/message/print.go b/message/print.go
new file mode 100644
index 0000000..305b7e5
--- /dev/null
+++ b/message/print.go
@@ -0,0 +1,1140 @@
+// +build ignore
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fmt
+
+import (
+	"errors"
+	"io"
+	"os"
+	"reflect"
+	"sync"
+	"unicode/utf8"
+)
+
+// Strings for use with buffer.WriteString.
+// This is less overhead than using buffer.Write with byte arrays.
+const (
+	commaSpaceString  = ", "
+	nilAngleString    = "<nil>"
+	nilParenString    = "(nil)"
+	nilString         = "nil"
+	mapString         = "map["
+	percentBangString = "%!"
+	missingString     = "(MISSING)"
+	badIndexString    = "(BADINDEX)"
+	panicString       = "(PANIC="
+	extraString       = "%!(EXTRA "
+	badWidthString    = "%!(BADWIDTH)"
+	badPrecString     = "%!(BADPREC)"
+	noVerbString      = "%!(NOVERB)"
+	invReflectString  = "<invalid reflect.Value>"
+)
+
+// State represents the printer state passed to custom formatters.
+// It provides access to the io.Writer interface plus information about
+// the flags and options for the operand's format specifier.
+type State interface {
+	// Write is the function to call to emit formatted output to be printed.
+	Write(b []byte) (n int, err error)
+	// Width returns the value of the width option and whether it has been set.
+	Width() (wid int, ok bool)
+	// Precision returns the value of the precision option and whether it has been set.
+	Precision() (prec int, ok bool)
+
+	// Flag reports whether the flag c, a character, has been set.
+	Flag(c int) bool
+}
+
+// Formatter is the interface implemented by values with a custom formatter.
+// The implementation of Format may call Sprint(f) or Fprint(f) etc.
+// to generate its output.
+type Formatter interface {
+	Format(f State, c rune)
+}
+
+// Stringer is implemented by any value that has a String method,
+// which defines the ``native'' format for that value.
+// The String method is used to print values passed as an operand
+// to any format that accepts a string or to an unformatted printer
+// such as Print.
+type Stringer interface {
+	String() string
+}
+
+// GoStringer is implemented by any value that has a GoString method,
+// which defines the Go syntax for that value.
+// The GoString method is used to print values passed as an operand
+// to a %#v format.
+type GoStringer interface {
+	GoString() string
+}
+
+// Use simple []byte instead of bytes.Buffer to avoid large dependency.
+type buffer []byte
+
+func (b *buffer) Write(p []byte) {
+	*b = append(*b, p...)
+}
+
+func (b *buffer) WriteString(s string) {
+	*b = append(*b, s...)
+}
+
+func (b *buffer) WriteByte(c byte) {
+	*b = append(*b, c)
+}
+
+func (bp *buffer) WriteRune(r rune) {
+	if r < utf8.RuneSelf {
+		*bp = append(*bp, byte(r))
+		return
+	}
+
+	b := *bp
+	n := len(b)
+	for n+utf8.UTFMax > cap(b) {
+		b = append(b, 0)
+	}
+	w := utf8.EncodeRune(b[n:n+utf8.UTFMax], r)
+	*bp = b[:n+w]
+}
+
+// pp is used to store a printer's state and is reused with sync.Pool to avoid allocations.
+type pp struct {
+	buf buffer
+
+	// arg holds the current item, as an interface{}.
+	arg interface{}
+
+	// value is used instead of arg for reflect values.
+	value reflect.Value
+
+	// fmt is used to format basic items such as integers or strings.
+	fmt fmt
+
+	// reordered records whether the format string used argument reordering.
+	reordered bool
+	// goodArgNum records whether the most recent reordering directive was valid.
+	goodArgNum bool
+	// panicking is set by catchPanic to avoid infinite panic, recover, panic, ... recursion.
+	panicking bool
+	// erroring is set when printing an error string to guard against calling handleMethods.
+	erroring bool
+}
+
+var ppFree = sync.Pool{
+	New: func() interface{} { return new(pp) },
+}
+
+// newPrinter allocates a new pp struct or grabs a cached one.
+func newPrinter() *pp {
+	p := ppFree.Get().(*pp)
+	p.panicking = false
+	p.erroring = false
+	p.fmt.init(&p.buf)
+	return p
+}
+
+// free saves used pp structs in ppFree; avoids an allocation per invocation.
+func (p *pp) free() {
+	p.buf = p.buf[:0]
+	p.arg = nil
+	p.value = reflect.Value{}
+	ppFree.Put(p)
+}
+
+func (p *pp) Width() (wid int, ok bool) { return p.fmt.wid, p.fmt.widPresent }
+
+func (p *pp) Precision() (prec int, ok bool) { return p.fmt.prec, p.fmt.precPresent }
+
+func (p *pp) Flag(b int) bool {
+	switch b {
+	case '-':
+		return p.fmt.minus
+	case '+':
+		return p.fmt.plus || p.fmt.plusV
+	case '#':
+		return p.fmt.sharp || p.fmt.sharpV
+	case ' ':
+		return p.fmt.space
+	case '0':
+		return p.fmt.zero
+	}
+	return false
+}
+
+// Implement Write so we can call Fprintf on a pp (through State), for
+// recursive use in custom verbs.
+func (p *pp) Write(b []byte) (ret int, err error) {
+	p.buf.Write(b)
+	return len(b), nil
+}
+
+// These routines end in 'f' and take a format string.
+
+// Fprintf formats according to a format specifier and writes to w.
+// It returns the number of bytes written and any write error encountered.
+func Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error) {
+	p := newPrinter()
+	p.doPrintf(format, a)
+	n, err = w.Write(p.buf)
+	p.free()
+	return
+}
+
+// Printf formats according to a format specifier and writes to standard output.
+// It returns the number of bytes written and any write error encountered.
+func Printf(format string, a ...interface{}) (n int, err error) {
+	return Fprintf(os.Stdout, format, a...)
+}
+
+// Sprintf formats according to a format specifier and returns the resulting string.
+func Sprintf(format string, a ...interface{}) string {
+	p := newPrinter()
+	p.doPrintf(format, a)
+	s := string(p.buf)
+	p.free()
+	return s
+}
+
+// Errorf formats according to a format specifier and returns the string
+// as a value that satisfies error.
+func Errorf(format string, a ...interface{}) error {
+	return errors.New(Sprintf(format, a...))
+}
+
+// These routines do not take a format string
+
+// Fprint formats using the default formats for its operands and writes to w.
+// Spaces are added between operands when neither is a string.
+// It returns the number of bytes written and any write error encountered.
+func Fprint(w io.Writer, a ...interface{}) (n int, err error) {
+	p := newPrinter()
+	p.doPrint(a)
+	n, err = w.Write(p.buf)
+	p.free()
+	return
+}
+
+// Print formats using the default formats for its operands and writes to standard output.
+// Spaces are added between operands when neither is a string.
+// It returns the number of bytes written and any write error encountered.
+func Print(a ...interface{}) (n int, err error) {
+	return Fprint(os.Stdout, a...)
+}
+
+// Sprint formats using the default formats for its operands and returns the resulting string.
+// Spaces are added between operands when neither is a string.
+func Sprint(a ...interface{}) string {
+	p := newPrinter()
+	p.doPrint(a)
+	s := string(p.buf)
+	p.free()
+	return s
+}
+
+// These routines end in 'ln', do not take a format string,
+// always add spaces between operands, and add a newline
+// after the last operand.
+
+// Fprintln formats using the default formats for its operands and writes to w.
+// Spaces are always added between operands and a newline is appended.
+// It returns the number of bytes written and any write error encountered.
+func Fprintln(w io.Writer, a ...interface{}) (n int, err error) {
+	p := newPrinter()
+	p.doPrintln(a)
+	n, err = w.Write(p.buf)
+	p.free()
+	return
+}
+
+// Println formats using the default formats for its operands and writes to standard output.
+// Spaces are always added between operands and a newline is appended.
+// It returns the number of bytes written and any write error encountered.
+func Println(a ...interface{}) (n int, err error) {
+	return Fprintln(os.Stdout, a...)
+}
+
+// Sprintln formats using the default formats for its operands and returns the resulting string.
+// Spaces are always added between operands and a newline is appended.
+func Sprintln(a ...interface{}) string {
+	p := newPrinter()
+	p.doPrintln(a)
+	s := string(p.buf)
+	p.free()
+	return s
+}
+
+// getField gets the i'th field of the struct value.
+// If the field is itself is an interface, return a value for
+// the thing inside the interface, not the interface itself.
+func getField(v reflect.Value, i int) reflect.Value {
+	val := v.Field(i)
+	if val.Kind() == reflect.Interface && !val.IsNil() {
+		val = val.Elem()
+	}
+	return val
+}
+
+// tooLarge reports whether the magnitude of the integer is
+// too large to be used as a formatting width or precision.
+func tooLarge(x int) bool {
+	const max int = 1e6
+	return x > max || x < -max
+}
+
+// parsenum converts ASCII to integer.  num is 0 (and isnum is false) if no number present.
+func parsenum(s string, start, end int) (num int, isnum bool, newi int) {
+	if start >= end {
+		return 0, false, end
+	}
+	for newi = start; newi < end && '0' <= s[newi] && s[newi] <= '9'; newi++ {
+		if tooLarge(num) {
+			return 0, false, end // Overflow; crazy long number most likely.
+		}
+		num = num*10 + int(s[newi]-'0')
+		isnum = true
+	}
+	return
+}
+
+func (p *pp) unknownType(v reflect.Value) {
+	if !v.IsValid() {
+		p.buf.WriteString(nilAngleString)
+		return
+	}
+	p.buf.WriteByte('?')
+	p.buf.WriteString(v.Type().String())
+	p.buf.WriteByte('?')
+}
+
+func (p *pp) badVerb(verb rune) {
+	p.erroring = true
+	p.buf.WriteString(percentBangString)
+	p.buf.WriteRune(verb)
+	p.buf.WriteByte('(')
+	switch {
+	case p.arg != nil:
+		p.buf.WriteString(reflect.TypeOf(p.arg).String())
+		p.buf.WriteByte('=')
+		p.printArg(p.arg, 'v')
+	case p.value.IsValid():
+		p.buf.WriteString(p.value.Type().String())
+		p.buf.WriteByte('=')
+		p.printValue(p.value, 'v', 0)
+	default:
+		p.buf.WriteString(nilAngleString)
+	}
+	p.buf.WriteByte(')')
+	p.erroring = false
+}
+
+func (p *pp) fmtBool(v bool, verb rune) {
+	switch verb {
+	case 't', 'v':
+		p.fmt.fmt_boolean(v)
+	default:
+		p.badVerb(verb)
+	}
+}
+
+// fmt0x64 formats a uint64 in hexadecimal and prefixes it with 0x or
+// not, as requested, by temporarily setting the sharp flag.
+func (p *pp) fmt0x64(v uint64, leading0x bool) {
+	sharp := p.fmt.sharp
+	p.fmt.sharp = leading0x
+	p.fmt.fmt_integer(v, 16, unsigned, ldigits)
+	p.fmt.sharp = sharp
+}
+
+// fmtInteger formats a signed or unsigned integer.
+func (p *pp) fmtInteger(v uint64, isSigned bool, verb rune) {
+	switch verb {
+	case 'v':
+		if p.fmt.sharpV && !isSigned {
+			p.fmt0x64(v, true)
+		} else {
+			p.fmt.fmt_integer(v, 10, isSigned, ldigits)
+		}
+	case 'd':
+		p.fmt.fmt_integer(v, 10, isSigned, ldigits)
+	case 'b':
+		p.fmt.fmt_integer(v, 2, isSigned, ldigits)
+	case 'o':
+		p.fmt.fmt_integer(v, 8, isSigned, ldigits)
+	case 'x':
+		p.fmt.fmt_integer(v, 16, isSigned, ldigits)
+	case 'X':
+		p.fmt.fmt_integer(v, 16, isSigned, udigits)
+	case 'c':
+		p.fmt.fmt_c(v)
+	case 'q':
+		if v <= utf8.MaxRune {
+			p.fmt.fmt_qc(v)
+		} else {
+			p.badVerb(verb)
+		}
+	case 'U':
+		p.fmt.fmt_unicode(v)
+	default:
+		p.badVerb(verb)
+	}
+}
+
+// fmtFloat formats a float. The default precision for each verb
+// is specified as last argument in the call to fmt_float.
+func (p *pp) fmtFloat(v float64, size int, verb rune) {
+	switch verb {
+	case 'v':
+		p.fmt.fmt_float(v, size, 'g', -1)
+	case 'b', 'g', 'G':
+		p.fmt.fmt_float(v, size, verb, -1)
+	case 'f', 'e', 'E':
+		p.fmt.fmt_float(v, size, verb, 6)
+	case 'F':
+		p.fmt.fmt_float(v, size, 'f', 6)
+	default:
+		p.badVerb(verb)
+	}
+}
+
+// fmtComplex formats a complex number v with
+// r = real(v) and j = imag(v) as (r+ji) using
+// fmtFloat for r and j formatting.
+func (p *pp) fmtComplex(v complex128, size int, verb rune) {
+	// Make sure any unsupported verbs are found before the
+	// calls to fmtFloat to not generate an incorrect error string.
+	switch verb {
+	case 'v', 'b', 'g', 'G', 'f', 'F', 'e', 'E':
+		oldPlus := p.fmt.plus
+		p.buf.WriteByte('(')
+		p.fmtFloat(real(v), size/2, verb)
+		// Imaginary part always has a sign.
+		p.fmt.plus = true
+		p.fmtFloat(imag(v), size/2, verb)
+		p.buf.WriteString("i)")
+		p.fmt.plus = oldPlus
+	default:
+		p.badVerb(verb)
+	}
+}
+
+func (p *pp) fmtString(v string, verb rune) {
+	switch verb {
+	case 'v':
+		if p.fmt.sharpV {
+			p.fmt.fmt_q(v)
+		} else {
+			p.fmt.fmt_s(v)
+		}
+	case 's':
+		p.fmt.fmt_s(v)
+	case 'x':
+		p.fmt.fmt_sx(v, ldigits)
+	case 'X':
+		p.fmt.fmt_sx(v, udigits)
+	case 'q':
+		p.fmt.fmt_q(v)
+	default:
+		p.badVerb(verb)
+	}
+}
+
+func (p *pp) fmtBytes(v []byte, verb rune, typeString string) {
+	switch verb {
+	case 'v', 'd':
+		if p.fmt.sharpV {
+			p.buf.WriteString(typeString)
+			if v == nil {
+				p.buf.WriteString(nilParenString)
+				return
+			}
+			p.buf.WriteByte('{')
+			for i, c := range v {
+				if i > 0 {
+					p.buf.WriteString(commaSpaceString)
+				}
+				p.fmt0x64(uint64(c), true)
+			}
+			p.buf.WriteByte('}')
+		} else {
+			p.buf.WriteByte('[')
+			for i, c := range v {
+				if i > 0 {
+					p.buf.WriteByte(' ')
+				}
+				p.fmt.fmt_integer(uint64(c), 10, unsigned, ldigits)
+			}
+			p.buf.WriteByte(']')
+		}
+	case 's':
+		p.fmt.fmt_s(string(v))
+	case 'x':
+		p.fmt.fmt_bx(v, ldigits)
+	case 'X':
+		p.fmt.fmt_bx(v, udigits)
+	case 'q':
+		p.fmt.fmt_q(string(v))
+	default:
+		p.printValue(reflect.ValueOf(v), verb, 0)
+	}
+}
+
+func (p *pp) fmtPointer(value reflect.Value, verb rune) {
+	var u uintptr
+	switch value.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr, reflect.Slice, reflect.UnsafePointer:
+		u = value.Pointer()
+	default:
+		p.badVerb(verb)
+		return
+	}
+
+	switch verb {
+	case 'v':
+		if p.fmt.sharpV {
+			p.buf.WriteByte('(')
+			p.buf.WriteString(value.Type().String())
+			p.buf.WriteString(")(")
+			if u == 0 {
+				p.buf.WriteString(nilString)
+			} else {
+				p.fmt0x64(uint64(u), true)
+			}
+			p.buf.WriteByte(')')
+		} else {
+			if u == 0 {
+				p.fmt.padString(nilAngleString)
+			} else {
+				p.fmt0x64(uint64(u), !p.fmt.sharp)
+			}
+		}
+	case 'p':
+		p.fmt0x64(uint64(u), !p.fmt.sharp)
+	case 'b', 'o', 'd', 'x', 'X':
+		p.fmtInteger(uint64(u), unsigned, verb)
+	default:
+		p.badVerb(verb)
+	}
+}
+
+func (p *pp) catchPanic(arg interface{}, verb rune) {
+	if err := recover(); err != nil {
+		// If it's a nil pointer, just say "<nil>". The likeliest causes are a
+		// Stringer that fails to guard against nil or a nil pointer for a
+		// value receiver, and in either case, "<nil>" is a nice result.
+		if v := reflect.ValueOf(arg); v.Kind() == reflect.Ptr && v.IsNil() {
+			p.buf.WriteString(nilAngleString)
+			return
+		}
+		// Otherwise print a concise panic message. Most of the time the panic
+		// value will print itself nicely.
+		if p.panicking {
+			// Nested panics; the recursion in printArg cannot succeed.
+			panic(err)
+		}
+
+		oldFlags := p.fmt.fmtFlags
+		// For this output we want default behavior.
+		p.fmt.clearflags()
+
+		p.buf.WriteString(percentBangString)
+		p.buf.WriteRune(verb)
+		p.buf.WriteString(panicString)
+		p.panicking = true
+		p.printArg(err, 'v')
+		p.panicking = false
+		p.buf.WriteByte(')')
+
+		p.fmt.fmtFlags = oldFlags
+	}
+}
+
+func (p *pp) handleMethods(verb rune) (handled bool) {
+	if p.erroring {
+		return
+	}
+	// Is it a Formatter?
+	if formatter, ok := p.arg.(Formatter); ok {
+		handled = true
+		defer p.catchPanic(p.arg, verb)
+		formatter.Format(p, verb)
+		return
+	}
+
+	// If we're doing Go syntax and the argument knows how to supply it, take care of it now.
+	if p.fmt.sharpV {
+		if stringer, ok := p.arg.(GoStringer); ok {
+			handled = true
+			defer p.catchPanic(p.arg, verb)
+			// Print the result of GoString unadorned.
+			p.fmt.fmt_s(stringer.GoString())
+			return
+		}
+	} else {
+		// If a string is acceptable according to the format, see if
+		// the value satisfies one of the string-valued interfaces.
+		// Println etc. set verb to %v, which is "stringable".
+		switch verb {
+		case 'v', 's', 'x', 'X', 'q':
+			// Is it an error or Stringer?
+			// The duplication in the bodies is necessary:
+			// setting handled and deferring catchPanic
+			// must happen before calling the method.
+			switch v := p.arg.(type) {
+			case error:
+				handled = true
+				defer p.catchPanic(p.arg, verb)
+				p.fmtString(v.Error(), verb)
+				return
+
+			case Stringer:
+				handled = true
+				defer p.catchPanic(p.arg, verb)
+				p.fmtString(v.String(), verb)
+				return
+			}
+		}
+	}
+	return false
+}
+
+func (p *pp) printArg(arg interface{}, verb rune) {
+	p.arg = arg
+	p.value = reflect.Value{}
+
+	if arg == nil {
+		switch verb {
+		case 'T', 'v':
+			p.fmt.padString(nilAngleString)
+		default:
+			p.badVerb(verb)
+		}
+		return
+	}
+
+	// Special processing considerations.
+	// %T (the value's type) and %p (its address) are special; we always do them first.
+	switch verb {
+	case 'T':
+		p.fmt.fmt_s(reflect.TypeOf(arg).String())
+		return
+	case 'p':
+		p.fmtPointer(reflect.ValueOf(arg), 'p')
+		return
+	}
+
+	// Some types can be done without reflection.
+	switch f := arg.(type) {
+	case bool:
+		p.fmtBool(f, verb)
+	case float32:
+		p.fmtFloat(float64(f), 32, verb)
+	case float64:
+		p.fmtFloat(f, 64, verb)
+	case complex64:
+		p.fmtComplex(complex128(f), 64, verb)
+	case complex128:
+		p.fmtComplex(f, 128, verb)
+	case int:
+		p.fmtInteger(uint64(f), signed, verb)
+	case int8:
+		p.fmtInteger(uint64(f), signed, verb)
+	case int16:
+		p.fmtInteger(uint64(f), signed, verb)
+	case int32:
+		p.fmtInteger(uint64(f), signed, verb)
+	case int64:
+		p.fmtInteger(uint64(f), signed, verb)
+	case uint:
+		p.fmtInteger(uint64(f), unsigned, verb)
+	case uint8:
+		p.fmtInteger(uint64(f), unsigned, verb)
+	case uint16:
+		p.fmtInteger(uint64(f), unsigned, verb)
+	case uint32:
+		p.fmtInteger(uint64(f), unsigned, verb)
+	case uint64:
+		p.fmtInteger(f, unsigned, verb)
+	case uintptr:
+		p.fmtInteger(uint64(f), unsigned, verb)
+	case string:
+		p.fmtString(f, verb)
+	case []byte:
+		p.fmtBytes(f, verb, "[]byte")
+	case reflect.Value:
+		// Handle extractable values with special methods
+		// since printValue does not handle them at depth 0.
+		if f.IsValid() && f.CanInterface() {
+			p.arg = f.Interface()
+			if p.handleMethods(verb) {
+				return
+			}
+		}
+		p.printValue(f, verb, 0)
+	default:
+		// If the type is not simple, it might have methods.
+		if !p.handleMethods(verb) {
+			// Need to use reflection, since the type had no
+			// interface methods that could be used for formatting.
+			p.printValue(reflect.ValueOf(f), verb, 0)
+		}
+	}
+}
+
+// printValue is similar to printArg but starts with a reflect value, not an interface{} value.
+// It does not handle 'p' and 'T' verbs because these should have been already handled by printArg.
+func (p *pp) printValue(value reflect.Value, verb rune, depth int) {
+	// Handle values with special methods if not already handled by printArg (depth == 0).
+	if depth > 0 && value.IsValid() && value.CanInterface() {
+		p.arg = value.Interface()
+		if p.handleMethods(verb) {
+			return
+		}
+	}
+	p.arg = nil
+	p.value = value
+
+	switch f := value; value.Kind() {
+	case reflect.Invalid:
+		if depth == 0 {
+			p.buf.WriteString(invReflectString)
+		} else {
+			switch verb {
+			case 'v':
+				p.buf.WriteString(nilAngleString)
+			default:
+				p.badVerb(verb)
+			}
+		}
+	case reflect.Bool:
+		p.fmtBool(f.Bool(), verb)
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		p.fmtInteger(uint64(f.Int()), signed, verb)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		p.fmtInteger(f.Uint(), unsigned, verb)
+	case reflect.Float32:
+		p.fmtFloat(f.Float(), 32, verb)
+	case reflect.Float64:
+		p.fmtFloat(f.Float(), 64, verb)
+	case reflect.Complex64:
+		p.fmtComplex(f.Complex(), 64, verb)
+	case reflect.Complex128:
+		p.fmtComplex(f.Complex(), 128, verb)
+	case reflect.String:
+		p.fmtString(f.String(), verb)
+	case reflect.Map:
+		if p.fmt.sharpV {
+			p.buf.WriteString(f.Type().String())
+			if f.IsNil() {
+				p.buf.WriteString(nilParenString)
+				return
+			}
+			p.buf.WriteByte('{')
+		} else {
+			p.buf.WriteString(mapString)
+		}
+		keys := f.MapKeys()
+		for i, key := range keys {
+			if i > 0 {
+				if p.fmt.sharpV {
+					p.buf.WriteString(commaSpaceString)
+				} else {
+					p.buf.WriteByte(' ')
+				}
+			}
+			p.printValue(key, verb, depth+1)
+			p.buf.WriteByte(':')
+			p.printValue(f.MapIndex(key), verb, depth+1)
+		}
+		if p.fmt.sharpV {
+			p.buf.WriteByte('}')
+		} else {
+			p.buf.WriteByte(']')
+		}
+	case reflect.Struct:
+		if p.fmt.sharpV {
+			p.buf.WriteString(f.Type().String())
+		}
+		p.buf.WriteByte('{')
+		for i := 0; i < f.NumField(); i++ {
+			if i > 0 {
+				if p.fmt.sharpV {
+					p.buf.WriteString(commaSpaceString)
+				} else {
+					p.buf.WriteByte(' ')
+				}
+			}
+			if p.fmt.plusV || p.fmt.sharpV {
+				if name := f.Type().Field(i).Name; name != "" {
+					p.buf.WriteString(name)
+					p.buf.WriteByte(':')
+				}
+			}
+			p.printValue(getField(f, i), verb, depth+1)
+		}
+		p.buf.WriteByte('}')
+	case reflect.Interface:
+		value := f.Elem()
+		if !value.IsValid() {
+			if p.fmt.sharpV {
+				p.buf.WriteString(f.Type().String())
+				p.buf.WriteString(nilParenString)
+			} else {
+				p.buf.WriteString(nilAngleString)
+			}
+		} else {
+			p.printValue(value, verb, depth+1)
+		}
+	case reflect.Array, reflect.Slice:
+		switch verb {
+		case 's', 'q', 'x', 'X':
+			// Handle byte and uint8 slices and arrays special for the above verbs.
+			t := f.Type()
+			if t.Elem().Kind() == reflect.Uint8 {
+				var bytes []byte
+				if f.Kind() == reflect.Slice {
+					bytes = f.Bytes()
+				} else if f.CanAddr() {
+					bytes = f.Slice(0, f.Len()).Bytes()
+				} else {
+					// We have an array, but we cannot Slice() a non-addressable array,
+					// so we build a slice by hand. This is a rare case but it would be nice
+					// if reflection could help a little more.
+					bytes = make([]byte, f.Len())
+					for i := range bytes {
+						bytes[i] = byte(f.Index(i).Uint())
+					}
+				}
+				p.fmtBytes(bytes, verb, t.String())
+				return
+			}
+		}
+		if p.fmt.sharpV {
+			p.buf.WriteString(f.Type().String())
+			if f.Kind() == reflect.Slice && f.IsNil() {
+				p.buf.WriteString(nilParenString)
+				return
+			}
+			p.buf.WriteByte('{')
+			for i := 0; i < f.Len(); i++ {
+				if i > 0 {
+					p.buf.WriteString(commaSpaceString)
+				}
+				p.printValue(f.Index(i), verb, depth+1)
+			}
+			p.buf.WriteByte('}')
+		} else {
+			p.buf.WriteByte('[')
+			for i := 0; i < f.Len(); i++ {
+				if i > 0 {
+					p.buf.WriteByte(' ')
+				}
+				p.printValue(f.Index(i), verb, depth+1)
+			}
+			p.buf.WriteByte(']')
+		}
+	case reflect.Ptr:
+		// pointer to array or slice or struct?  ok at top level
+		// but not embedded (avoid loops)
+		if depth == 0 && f.Pointer() != 0 {
+			switch a := f.Elem(); a.Kind() {
+			case reflect.Array, reflect.Slice, reflect.Struct, reflect.Map:
+				p.buf.WriteByte('&')
+				p.printValue(a, verb, depth+1)
+				return
+			}
+		}
+		fallthrough
+	case reflect.Chan, reflect.Func, reflect.UnsafePointer:
+		p.fmtPointer(f, verb)
+	default:
+		p.unknownType(f)
+	}
+}
+
+// intFromArg gets the argNumth element of a. On return, isInt reports whether the argument has integer type.
+func intFromArg(a []interface{}, argNum int) (num int, isInt bool, newArgNum int) {
+	newArgNum = argNum
+	if argNum < len(a) {
+		num, isInt = a[argNum].(int) // Almost always OK.
+		if !isInt {
+			// Work harder.
+			switch v := reflect.ValueOf(a[argNum]); v.Kind() {
+			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+				n := v.Int()
+				if int64(int(n)) == n {
+					num = int(n)
+					isInt = true
+				}
+			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+				n := v.Uint()
+				if int64(n) >= 0 && uint64(int(n)) == n {
+					num = int(n)
+					isInt = true
+				}
+			default:
+				// Already 0, false.
+			}
+		}
+		newArgNum = argNum + 1
+		if tooLarge(num) {
+			num = 0
+			isInt = false
+		}
+	}
+	return
+}
+
+// parseArgNumber returns the value of the bracketed number, minus 1
+// (explicit argument numbers are one-indexed but we want zero-indexed).
+// The opening bracket is known to be present at format[0].
+// The returned values are the index, the number of bytes to consume
+// up to the closing paren, if present, and whether the number parsed
+// ok. The bytes to consume will be 1 if no closing paren is present.
+func parseArgNumber(format string) (index int, wid int, ok bool) {
+	// There must be at least 3 bytes: [n].
+	if len(format) < 3 {
+		return 0, 1, false
+	}
+
+	// Find closing bracket.
+	for i := 1; i < len(format); i++ {
+		if format[i] == ']' {
+			width, ok, newi := parsenum(format, 1, i)
+			if !ok || newi != i {
+				return 0, i + 1, false
+			}
+			return width - 1, i + 1, true // arg numbers are one-indexed and skip paren.
+		}
+	}
+	return 0, 1, false
+}
+
+// argNumber returns the next argument to evaluate, which is either the value of the passed-in
+// argNum or the value of the bracketed integer that begins format[i:]. It also returns
+// the new value of i, that is, the index of the next byte of the format to process.
+func (p *pp) argNumber(argNum int, format string, i int, numArgs int) (newArgNum, newi int, found bool) {
+	if len(format) <= i || format[i] != '[' {
+		return argNum, i, false
+	}
+	p.reordered = true
+	index, wid, ok := parseArgNumber(format[i:])
+	if ok && 0 <= index && index < numArgs {
+		return index, i + wid, true
+	}
+	p.goodArgNum = false
+	return argNum, i + wid, ok
+}
+
+func (p *pp) badArgNum(verb rune) {
+	p.buf.WriteString(percentBangString)
+	p.buf.WriteRune(verb)
+	p.buf.WriteString(badIndexString)
+}
+
+func (p *pp) missingArg(verb rune) {
+	p.buf.WriteString(percentBangString)
+	p.buf.WriteRune(verb)
+	p.buf.WriteString(missingString)
+}
+
+func (p *pp) doPrintf(format string, a []interface{}) {
+	end := len(format)
+	argNum := 0         // we process one argument per non-trivial format
+	afterIndex := false // previous item in format was an index like [3].
+	p.reordered = false
+formatLoop:
+	for i := 0; i < end; {
+		p.goodArgNum = true
+		lasti := i
+		for i < end && format[i] != '%' {
+			i++
+		}
+		if i > lasti {
+			p.buf.WriteString(format[lasti:i])
+		}
+		if i >= end {
+			// done processing format string
+			break
+		}
+
+		// Process one verb
+		i++
+
+		// Do we have flags?
+		p.fmt.clearflags()
+	simpleFormat:
+		for ; i < end; i++ {
+			c := format[i]
+			switch c {
+			case '#':
+				p.fmt.sharp = true
+			case '0':
+				p.fmt.zero = !p.fmt.minus // Only allow zero padding to the left.
+			case '+':
+				p.fmt.plus = true
+			case '-':
+				p.fmt.minus = true
+				p.fmt.zero = false // Do not pad with zeros to the right.
+			case ' ':
+				p.fmt.space = true
+			default:
+				// Fast path for common case of ascii lower case simple verbs
+				// without precision or width or argument indices.
+				if 'a' <= c && c <= 'z' && argNum < len(a) {
+					if c == 'v' {
+						// Go syntax
+						p.fmt.sharpV = p.fmt.sharp
+						p.fmt.sharp = false
+						// Struct-field syntax
+						p.fmt.plusV = p.fmt.plus
+						p.fmt.plus = false
+					}
+					p.printArg(a[argNum], rune(c))
+					argNum++
+					i++
+					continue formatLoop
+				}
+				// Format is more complex than simple flags and a verb or is malformed.
+				break simpleFormat
+			}
+		}
+
+		// Do we have an explicit argument index?
+		argNum, i, afterIndex = p.argNumber(argNum, format, i, len(a))
+
+		// Do we have width?
+		if i < end && format[i] == '*' {
+			i++
+			p.fmt.wid, p.fmt.widPresent, argNum = intFromArg(a, argNum)
+
+			if !p.fmt.widPresent {
+				p.buf.WriteString(badWidthString)
+			}
+
+			// We have a negative width, so take its value and ensure
+			// that the minus flag is set
+			if p.fmt.wid < 0 {
+				p.fmt.wid = -p.fmt.wid
+				p.fmt.minus = true
+				p.fmt.zero = false // Do not pad with zeros to the right.
+			}
+			afterIndex = false
+		} else {
+			p.fmt.wid, p.fmt.widPresent, i = parsenum(format, i, end)
+			if afterIndex && p.fmt.widPresent { // "%[3]2d"
+				p.goodArgNum = false
+			}
+		}
+
+		// Do we have precision?
+		if i+1 < end && format[i] == '.' {
+			i++
+			if afterIndex { // "%[3].2d"
+				p.goodArgNum = false
+			}
+			argNum, i, afterIndex = p.argNumber(argNum, format, i, len(a))
+			if i < end && format[i] == '*' {
+				i++
+				p.fmt.prec, p.fmt.precPresent, argNum = intFromArg(a, argNum)
+				// Negative precision arguments don't make sense
+				if p.fmt.prec < 0 {
+					p.fmt.prec = 0
+					p.fmt.precPresent = false
+				}
+				if !p.fmt.precPresent {
+					p.buf.WriteString(badPrecString)
+				}
+				afterIndex = false
+			} else {
+				p.fmt.prec, p.fmt.precPresent, i = parsenum(format, i, end)
+				if !p.fmt.precPresent {
+					p.fmt.prec = 0
+					p.fmt.precPresent = true
+				}
+			}
+		}
+
+		if !afterIndex {
+			argNum, i, afterIndex = p.argNumber(argNum, format, i, len(a))
+		}
+
+		if i >= end {
+			p.buf.WriteString(noVerbString)
+			break
+		}
+
+		verb, w := utf8.DecodeRuneInString(format[i:])
+		i += w
+
+		switch {
+		case verb == '%': // Percent does not absorb operands and ignores f.wid and f.prec.
+			p.buf.WriteByte('%')
+		case !p.goodArgNum:
+			p.badArgNum(verb)
+		case argNum >= len(a): // No argument left over to print for the current verb.
+			p.missingArg(verb)
+		case verb == 'v':
+			// Go syntax
+			p.fmt.sharpV = p.fmt.sharp
+			p.fmt.sharp = false
+			// Struct-field syntax
+			p.fmt.plusV = p.fmt.plus
+			p.fmt.plus = false
+			fallthrough
+		default:
+			p.printArg(a[argNum], verb)
+			argNum++
+		}
+	}
+
+	// Check for extra arguments unless the call accessed the arguments
+	// out of order, in which case it's too expensive to detect if they've all
+	// been used and arguably OK if they're not.
+	if !p.reordered && argNum < len(a) {
+		p.fmt.clearflags()
+		p.buf.WriteString(extraString)
+		for i, arg := range a[argNum:] {
+			if i > 0 {
+				p.buf.WriteString(commaSpaceString)
+			}
+			if arg == nil {
+				p.buf.WriteString(nilAngleString)
+			} else {
+				p.buf.WriteString(reflect.TypeOf(arg).String())
+				p.buf.WriteByte('=')
+				p.printArg(arg, 'v')
+			}
+		}
+		p.buf.WriteByte(')')
+	}
+}
+
+func (p *pp) doPrint(a []interface{}) {
+	prevString := false
+	for argNum, arg := range a {
+		isString := arg != nil && reflect.TypeOf(arg).Kind() == reflect.String
+		// Add a space between two non-string arguments.
+		if argNum > 0 && !isString && !prevString {
+			p.buf.WriteByte(' ')
+		}
+		p.printArg(arg, 'v')
+		prevString = isString
+	}
+}
+
+// doPrintln is like doPrint but always adds a space between arguments
+// and a newline after the last argument.
+func (p *pp) doPrintln(a []interface{}) {
+	for argNum, arg := range a {
+		if argNum > 0 {
+			p.buf.WriteByte(' ')
+		}
+		p.printArg(arg, 'v')
+	}
+	p.buf.WriteByte('\n')
+}