Adding upstream version 1.18.10.upstream/1.18.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1331 insertions, 0 deletions

diff --git a/src/fmt/scan_test.go b/src/fmt/scan_test.go
new file mode 100644
index 0000000..da0dfd1
--- /dev/null
+++ b/src/fmt/scan_test.go
@@ -0,0 +1,1331 @@
+// 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 (
+	"bufio"
+	"bytes"
+	"errors"
+	. "fmt"
+	"io"
+	"math"
+	"reflect"
+	"regexp"
+	"strings"
+	"testing"
+	"testing/iotest"
+	"unicode/utf8"
+)
+
+type ScanTest struct {
+	text string
+	in   any
+	out  any
+}
+
+type ScanfTest struct {
+	format string
+	text   string
+	in     any
+	out    any
+}
+
+type ScanfMultiTest struct {
+	format string
+	text   string
+	in     []any
+	out    []any
+	err    string
+}
+
+var (
+	boolVal              bool
+	intVal               int
+	int8Val              int8
+	int16Val             int16
+	int32Val             int32
+	int64Val             int64
+	uintVal              uint
+	uint8Val             uint8
+	uint16Val            uint16
+	uint32Val            uint32
+	uint64Val            uint64
+	float32Val           float32
+	float64Val           float64
+	stringVal            string
+	bytesVal             []byte
+	runeVal              rune
+	complex64Val         complex64
+	complex128Val        complex128
+	renamedBoolVal       renamedBool
+	renamedIntVal        renamedInt
+	renamedInt8Val       renamedInt8
+	renamedInt16Val      renamedInt16
+	renamedInt32Val      renamedInt32
+	renamedInt64Val      renamedInt64
+	renamedUintVal       renamedUint
+	renamedUint8Val      renamedUint8
+	renamedUint16Val     renamedUint16
+	renamedUint32Val     renamedUint32
+	renamedUint64Val     renamedUint64
+	renamedUintptrVal    renamedUintptr
+	renamedStringVal     renamedString
+	renamedBytesVal      renamedBytes
+	renamedFloat32Val    renamedFloat32
+	renamedFloat64Val    renamedFloat64
+	renamedComplex64Val  renamedComplex64
+	renamedComplex128Val renamedComplex128
+)
+
+// Xs accepts any non-empty run of the verb character
+type Xs string
+
+func (x *Xs) Scan(state ScanState, verb rune) error {
+	tok, err := state.Token(true, func(r rune) bool { return r == verb })
+	if err != nil {
+		return err
+	}
+	s := string(tok)
+	if !regexp.MustCompile("^" + string(verb) + "+$").MatchString(s) {
+		return errors.New("syntax error for xs")
+	}
+	*x = Xs(s)
+	return nil
+}
+
+var xVal Xs
+
+// IntString accepts an integer followed immediately by a string.
+// It tests the embedding of a scan within a scan.
+type IntString struct {
+	i int
+	s string
+}
+
+func (s *IntString) Scan(state ScanState, verb rune) error {
+	if _, err := Fscan(state, &s.i); err != nil {
+		return err
+	}
+
+	tok, err := state.Token(true, nil)
+	if err != nil {
+		return err
+	}
+	s.s = string(tok)
+	return nil
+}
+
+var intStringVal IntString
+
+var scanTests = []ScanTest{
+	// Basic types
+	{"T\n", &boolVal, true},  // boolean test vals toggle to be sure they are written
+	{"F\n", &boolVal, false}, // restored to zero value
+	{"21\n", &intVal, 21},
+	{"2_1\n", &intVal, 21},
+	{"0\n", &intVal, 0},
+	{"000\n", &intVal, 0},
+	{"0x10\n", &intVal, 0x10},
+	{"0x_1_0\n", &intVal, 0x10},
+	{"-0x10\n", &intVal, -0x10},
+	{"0377\n", &intVal, 0377},
+	{"0_3_7_7\n", &intVal, 0377},
+	{"0o377\n", &intVal, 0377},
+	{"0o_3_7_7\n", &intVal, 0377},
+	{"-0377\n", &intVal, -0377},
+	{"-0o377\n", &intVal, -0377},
+	{"0\n", &uintVal, uint(0)},
+	{"000\n", &uintVal, uint(0)},
+	{"0x10\n", &uintVal, uint(0x10)},
+	{"0377\n", &uintVal, uint(0377)},
+	{"22\n", &int8Val, int8(22)},
+	{"23\n", &int16Val, int16(23)},
+	{"24\n", &int32Val, int32(24)},
+	{"25\n", &int64Val, int64(25)},
+	{"127\n", &int8Val, int8(127)},
+	{"-21\n", &intVal, -21},
+	{"-22\n", &int8Val, int8(-22)},
+	{"-23\n", &int16Val, int16(-23)},
+	{"-24\n", &int32Val, int32(-24)},
+	{"-25\n", &int64Val, int64(-25)},
+	{"-128\n", &int8Val, int8(-128)},
+	{"+21\n", &intVal, +21},
+	{"+22\n", &int8Val, int8(+22)},
+	{"+23\n", &int16Val, int16(+23)},
+	{"+24\n", &int32Val, int32(+24)},
+	{"+25\n", &int64Val, int64(+25)},
+	{"+127\n", &int8Val, int8(+127)},
+	{"26\n", &uintVal, uint(26)},
+	{"27\n", &uint8Val, uint8(27)},
+	{"28\n", &uint16Val, uint16(28)},
+	{"29\n", &uint32Val, uint32(29)},
+	{"30\n", &uint64Val, uint64(30)},
+	{"255\n", &uint8Val, uint8(255)},
+	{"32767\n", &int16Val, int16(32767)},
+	{"2.3\n", &float64Val, 2.3},
+	{"2.3e1\n", &float32Val, float32(2.3e1)},
+	{"2.3e2\n", &float64Val, 2.3e2},
+	{"2.3p2\n", &float64Val, 2.3 * 4},
+	{"2.3p+2\n", &float64Val, 2.3 * 4},
+	{"2.3p+66\n", &float64Val, 2.3 * (1 << 66)},
+	{"2.3p-66\n", &float64Val, 2.3 / (1 << 66)},
+	{"0x2.3p-66\n", &float64Val, float64(0x23) / (1 << 70)},
+	{"2_3.4_5\n", &float64Val, 23.45},
+	{"2.35\n", &stringVal, "2.35"},
+	{"2345678\n", &bytesVal, []byte("2345678")},
+	{"(3.4e1-2i)\n", &complex128Val, 3.4e1 - 2i},
+	{"-3.45e1-3i\n", &complex64Val, complex64(-3.45e1 - 3i)},
+	{"-.45e1-1e2i\n", &complex128Val, complex128(-.45e1 - 100i)},
+	{"-.4_5e1-1E2i\n", &complex128Val, complex128(-.45e1 - 100i)},
+	{"0x1.0p1+0x1.0P2i\n", &complex128Val, complex128(2 + 4i)},
+	{"-0x1p1-0x1p2i\n", &complex128Val, complex128(-2 - 4i)},
+	{"-0x1ep-1-0x1p2i\n", &complex128Val, complex128(-15 - 4i)},
+	{"-0x1_Ep-1-0x1p0_2i\n", &complex128Val, complex128(-15 - 4i)},
+	{"hello\n", &stringVal, "hello"},
+
+	// Carriage-return followed by newline. (We treat \r\n as \n always.)
+	{"hello\r\n", &stringVal, "hello"},
+	{"27\r\n", &uint8Val, uint8(27)},
+
+	// Renamed types
+	{"true\n", &renamedBoolVal, renamedBool(true)},
+	{"F\n", &renamedBoolVal, renamedBool(false)},
+	{"101\n", &renamedIntVal, renamedInt(101)},
+	{"102\n", &renamedIntVal, renamedInt(102)},
+	{"103\n", &renamedUintVal, renamedUint(103)},
+	{"104\n", &renamedUintVal, renamedUint(104)},
+	{"105\n", &renamedInt8Val, renamedInt8(105)},
+	{"106\n", &renamedInt16Val, renamedInt16(106)},
+	{"107\n", &renamedInt32Val, renamedInt32(107)},
+	{"108\n", &renamedInt64Val, renamedInt64(108)},
+	{"109\n", &renamedUint8Val, renamedUint8(109)},
+	{"110\n", &renamedUint16Val, renamedUint16(110)},
+	{"111\n", &renamedUint32Val, renamedUint32(111)},
+	{"112\n", &renamedUint64Val, renamedUint64(112)},
+	{"113\n", &renamedUintptrVal, renamedUintptr(113)},
+	{"114\n", &renamedStringVal, renamedString("114")},
+	{"115\n", &renamedBytesVal, renamedBytes([]byte("115"))},
+
+	// Custom scanners.
+	{"  vvv ", &xVal, Xs("vvv")},
+	{" 1234hello", &intStringVal, IntString{1234, "hello"}},
+
+	// Fixed bugs
+	{"2147483648\n", &int64Val, int64(2147483648)}, // was: integer overflow
+}
+
+var scanfTests = []ScanfTest{
+	{"%v", "TRUE\n", &boolVal, true},
+	{"%t", "false\n", &boolVal, false},
+	{"%v", "-71\n", &intVal, -71},
+	{"%v", "-7_1\n", &intVal, -71},
+	{"%v", "0b111\n", &intVal, 7},
+	{"%v", "0b_1_1_1\n", &intVal, 7},
+	{"%v", "0377\n", &intVal, 0377},
+	{"%v", "0_3_7_7\n", &intVal, 0377},
+	{"%v", "0o377\n", &intVal, 0377},
+	{"%v", "0o_3_7_7\n", &intVal, 0377},
+	{"%v", "0x44\n", &intVal, 0x44},
+	{"%v", "0x_4_4\n", &intVal, 0x44},
+	{"%d", "72\n", &intVal, 72},
+	{"%c", "a\n", &runeVal, 'a'},
+	{"%c", "\u5072\n", &runeVal, '\u5072'},
+	{"%c", "\u1234\n", &runeVal, '\u1234'},
+	{"%d", "73\n", &int8Val, int8(73)},
+	{"%d", "+74\n", &int16Val, int16(74)},
+	{"%d", "75\n", &int32Val, int32(75)},
+	{"%d", "76\n", &int64Val, int64(76)},
+	{"%b", "1001001\n", &intVal, 73},
+	{"%o", "075\n", &intVal, 075},
+	{"%x", "a75\n", &intVal, 0xa75},
+	{"%v", "71\n", &uintVal, uint(71)},
+	{"%d", "72\n", &uintVal, uint(72)},
+	{"%d", "7_2\n", &uintVal, uint(7)}, // only %v takes underscores
+	{"%d", "73\n", &uint8Val, uint8(73)},
+	{"%d", "74\n", &uint16Val, uint16(74)},
+	{"%d", "75\n", &uint32Val, uint32(75)},
+	{"%d", "76\n", &uint64Val, uint64(76)},
+	{"%b", "1001001\n", &uintVal, uint(73)},
+	{"%b", "100_1001\n", &uintVal, uint(4)},
+	{"%o", "075\n", &uintVal, uint(075)},
+	{"%o", "07_5\n", &uintVal, uint(07)}, // only %v takes underscores
+	{"%x", "a75\n", &uintVal, uint(0xa75)},
+	{"%x", "A75\n", &uintVal, uint(0xa75)},
+	{"%x", "A7_5\n", &uintVal, uint(0xa7)}, // only %v takes underscores
+	{"%U", "U+1234\n", &intVal, int(0x1234)},
+	{"%U", "U+4567\n", &uintVal, uint(0x4567)},
+
+	{"%e", "2.3\n", &float64Val, 2.3},
+	{"%E", "2.3e1\n", &float32Val, float32(2.3e1)},
+	{"%f", "2.3e2\n", &float64Val, 2.3e2},
+	{"%g", "2.3p2\n", &float64Val, 2.3 * 4},
+	{"%G", "2.3p+2\n", &float64Val, 2.3 * 4},
+	{"%v", "2.3p+66\n", &float64Val, 2.3 * (1 << 66)},
+	{"%f", "2.3p-66\n", &float64Val, 2.3 / (1 << 66)},
+	{"%G", "0x2.3p-66\n", &float64Val, float64(0x23) / (1 << 70)},
+	{"%E", "2_3.4_5\n", &float64Val, 23.45},
+
+	// Strings
+	{"%s", "using-%s\n", &stringVal, "using-%s"},
+	{"%x", "7573696e672d2578\n", &stringVal, "using-%x"},
+	{"%X", "7573696E672D2558\n", &stringVal, "using-%X"},
+	{"%q", `"quoted\twith\\do\u0075bl\x65s"` + "\n", &stringVal, "quoted\twith\\doubles"},
+	{"%q", "`quoted with backs`\n", &stringVal, "quoted with backs"},
+
+	// Byte slices
+	{"%s", "bytes-%s\n", &bytesVal, []byte("bytes-%s")},
+	{"%x", "62797465732d2578\n", &bytesVal, []byte("bytes-%x")},
+	{"%X", "62797465732D2558\n", &bytesVal, []byte("bytes-%X")},
+	{"%q", `"bytes\rwith\vdo\u0075bl\x65s"` + "\n", &bytesVal, []byte("bytes\rwith\vdoubles")},
+	{"%q", "`bytes with backs`\n", &bytesVal, []byte("bytes with backs")},
+
+	// Renamed types
+	{"%v\n", "true\n", &renamedBoolVal, renamedBool(true)},
+	{"%t\n", "F\n", &renamedBoolVal, renamedBool(false)},
+	{"%v", "101\n", &renamedIntVal, renamedInt(101)},
+	{"%c", "\u0101\n", &renamedIntVal, renamedInt('\u0101')},
+	{"%o", "0146\n", &renamedIntVal, renamedInt(102)},
+	{"%v", "103\n", &renamedUintVal, renamedUint(103)},
+	{"%d", "104\n", &renamedUintVal, renamedUint(104)},
+	{"%d", "105\n", &renamedInt8Val, renamedInt8(105)},
+	{"%d", "106\n", &renamedInt16Val, renamedInt16(106)},
+	{"%d", "107\n", &renamedInt32Val, renamedInt32(107)},
+	{"%d", "108\n", &renamedInt64Val, renamedInt64(108)},
+	{"%x", "6D\n", &renamedUint8Val, renamedUint8(109)},
+	{"%o", "0156\n", &renamedUint16Val, renamedUint16(110)},
+	{"%d", "111\n", &renamedUint32Val, renamedUint32(111)},
+	{"%d", "112\n", &renamedUint64Val, renamedUint64(112)},
+	{"%d", "113\n", &renamedUintptrVal, renamedUintptr(113)},
+	{"%s", "114\n", &renamedStringVal, renamedString("114")},
+	{"%q", "\"1155\"\n", &renamedBytesVal, renamedBytes([]byte("1155"))},
+	{"%g", "116e1\n", &renamedFloat32Val, renamedFloat32(116e1)},
+	{"%g", "-11.7e+1", &renamedFloat64Val, renamedFloat64(-11.7e+1)},
+	{"%g", "11+6e1i\n", &renamedComplex64Val, renamedComplex64(11 + 6e1i)},
+	{"%g", "-11.+7e+1i", &renamedComplex128Val, renamedComplex128(-11. + 7e+1i)},
+
+	// Interesting formats
+	{"here is\tthe value:%d", "here is   the\tvalue:118\n", &intVal, 118},
+	{"%% %%:%d", "% %:119\n", &intVal, 119},
+	{"%d%%", "42%", &intVal, 42}, // %% at end of string.
+
+	// Corner cases
+	{"%x", "FFFFFFFF\n", &uint32Val, uint32(0xFFFFFFFF)},
+
+	// Custom scanner.
+	{"%s", "  sss ", &xVal, Xs("sss")},
+	{"%2s", "sssss", &xVal, Xs("ss")},
+
+	// Fixed bugs
+	{"%d\n", "27\n", &intVal, 27},         // ok
+	{"%d\n", "28 \n", &intVal, 28},        // was: "unexpected newline"
+	{"%v", "0", &intVal, 0},               // was: "EOF"; 0 was taken as base prefix and not counted.
+	{"%v", "0", &uintVal, uint(0)},        // was: "EOF"; 0 was taken as base prefix and not counted.
+	{"%c", " ", &uintVal, uint(' ')},      // %c must accept a blank.
+	{"%c", "\t", &uintVal, uint('\t')},    // %c must accept any space.
+	{"%c", "\n", &uintVal, uint('\n')},    // %c must accept any space.
+	{"%d%%", "23%\n", &uintVal, uint(23)}, // %% matches literal %.
+	{"%%%d", "%23\n", &uintVal, uint(23)}, // %% matches literal %.
+
+	// space handling
+	{"%d", "27", &intVal, 27},
+	{"%d", "27 ", &intVal, 27},
+	{"%d", " 27", &intVal, 27},
+	{"%d", " 27 ", &intVal, 27},
+
+	{"X%d", "X27", &intVal, 27},
+	{"X%d", "X27 ", &intVal, 27},
+	{"X%d", "X 27", &intVal, 27},
+	{"X%d", "X 27 ", &intVal, 27},
+
+	{"X %d", "X27", &intVal, nil},  // expected space in input to match format
+	{"X %d", "X27 ", &intVal, nil}, // expected space in input to match format
+	{"X %d", "X 27", &intVal, 27},
+	{"X %d", "X 27 ", &intVal, 27},
+
+	{"%dX", "27X", &intVal, 27},
+	{"%dX", "27 X", &intVal, nil}, // input does not match format
+	{"%dX", " 27X", &intVal, 27},
+	{"%dX", " 27 X", &intVal, nil}, // input does not match format
+
+	{"%d X", "27X", &intVal, nil}, // expected space in input to match format
+	{"%d X", "27 X", &intVal, 27},
+	{"%d X", " 27X", &intVal, nil}, // expected space in input to match format
+	{"%d X", " 27 X", &intVal, 27},
+
+	{"X %d X", "X27X", &intVal, nil},  // expected space in input to match format
+	{"X %d X", "X27 X", &intVal, nil}, // expected space in input to match format
+	{"X %d X", "X 27X", &intVal, nil}, // expected space in input to match format
+	{"X %d X", "X 27 X", &intVal, 27},
+
+	{"X %s X", "X27X", &stringVal, nil},  // expected space in input to match format
+	{"X %s X", "X27 X", &stringVal, nil}, // expected space in input to match format
+	{"X %s X", "X 27X", &stringVal, nil}, // unexpected EOF
+	{"X %s X", "X 27 X", &stringVal, "27"},
+
+	{"X%sX", "X27X", &stringVal, nil},   // unexpected EOF
+	{"X%sX", "X27 X", &stringVal, nil},  // input does not match format
+	{"X%sX", "X 27X", &stringVal, nil},  // unexpected EOF
+	{"X%sX", "X 27 X", &stringVal, nil}, // input does not match format
+
+	{"X%s", "X27", &stringVal, "27"},
+	{"X%s", "X27 ", &stringVal, "27"},
+	{"X%s", "X 27", &stringVal, "27"},
+	{"X%s", "X 27 ", &stringVal, "27"},
+
+	{"X%dX", "X27X", &intVal, 27},
+	{"X%dX", "X27 X", &intVal, nil}, // input does not match format
+	{"X%dX", "X 27X", &intVal, 27},
+	{"X%dX", "X 27 X", &intVal, nil}, // input does not match format
+
+	{"X%dX", "X27X", &intVal, 27},
+	{"X%dX", "X27X ", &intVal, 27},
+	{"X%dX", " X27X", &intVal, nil},  // input does not match format
+	{"X%dX", " X27X ", &intVal, nil}, // input does not match format
+
+	{"X%dX\n", "X27X", &intVal, 27},
+	{"X%dX \n", "X27X ", &intVal, 27},
+	{"X%dX\n", "X27X\n", &intVal, 27},
+	{"X%dX\n", "X27X \n", &intVal, 27},
+
+	{"X%dX \n", "X27X", &intVal, 27},
+	{"X%dX \n", "X27X ", &intVal, 27},
+	{"X%dX \n", "X27X\n", &intVal, 27},
+	{"X%dX \n", "X27X \n", &intVal, 27},
+
+	{"X%c", "X\n", &runeVal, '\n'},
+	{"X%c", "X \n", &runeVal, ' '},
+	{"X %c", "X!", &runeVal, nil},  // expected space in input to match format
+	{"X %c", "X\n", &runeVal, nil}, // newline in input does not match format
+	{"X %c", "X !", &runeVal, '!'},
+	{"X %c", "X \n", &runeVal, '\n'},
+
+	{" X%dX", "X27X", &intVal, nil},  // expected space in input to match format
+	{" X%dX", "X27X ", &intVal, nil}, // expected space in input to match format
+	{" X%dX", " X27X", &intVal, 27},
+	{" X%dX", " X27X ", &intVal, 27},
+
+	{"X%dX ", "X27X", &intVal, 27},
+	{"X%dX ", "X27X ", &intVal, 27},
+	{"X%dX ", " X27X", &intVal, nil},  // input does not match format
+	{"X%dX ", " X27X ", &intVal, nil}, // input does not match format
+
+	{" X%dX ", "X27X", &intVal, nil},  // expected space in input to match format
+	{" X%dX ", "X27X ", &intVal, nil}, // expected space in input to match format
+	{" X%dX ", " X27X", &intVal, 27},
+	{" X%dX ", " X27X ", &intVal, 27},
+
+	{"%d\nX", "27\nX", &intVal, 27},
+	{"%dX\n X", "27X\n X", &intVal, 27},
+}
+
+var overflowTests = []ScanTest{
+	{"128", &int8Val, 0},
+	{"32768", &int16Val, 0},
+	{"-129", &int8Val, 0},
+	{"-32769", &int16Val, 0},
+	{"256", &uint8Val, 0},
+	{"65536", &uint16Val, 0},
+	{"1e100", &float32Val, 0},
+	{"1e500", &float64Val, 0},
+	{"(1e100+0i)", &complex64Val, 0},
+	{"(1+1e100i)", &complex64Val, 0},
+	{"(1-1e500i)", &complex128Val, 0},
+}
+
+var truth bool
+var i, j, k int
+var f float64
+var s, t string
+var c complex128
+var x, y Xs
+var z IntString
+var r1, r2, r3 rune
+
+var multiTests = []ScanfMultiTest{
+	{"", "", []any{}, []any{}, ""},
+	{"%d", "23", args(&i), args(23), ""},
+	{"%2s%3s", "22333", args(&s, &t), args("22", "333"), ""},
+	{"%2d%3d", "44555", args(&i, &j), args(44, 555), ""},
+	{"%2d.%3d", "66.777", args(&i, &j), args(66, 777), ""},
+	{"%d, %d", "23, 18", args(&i, &j), args(23, 18), ""},
+	{"%3d22%3d", "33322333", args(&i, &j), args(333, 333), ""},
+	{"%6vX=%3fY", "3+2iX=2.5Y", args(&c, &f), args((3 + 2i), 2.5), ""},
+	{"%d%s", "123abc", args(&i, &s), args(123, "abc"), ""},
+	{"%c%c%c", "2\u50c2X", args(&r1, &r2, &r3), args('2', '\u50c2', 'X'), ""},
+	{"%5s%d", " 1234567 ", args(&s, &i), args("12345", 67), ""},
+	{"%5s%d", " 12 34 567 ", args(&s, &i), args("12", 34), ""},
+
+	// Custom scanners.
+	{"%e%f", "eefffff", args(&x, &y), args(Xs("ee"), Xs("fffff")), ""},
+	{"%4v%s", "12abcd", args(&z, &s), args(IntString{12, "ab"}, "cd"), ""},
+
+	// Errors
+	{"%t", "23 18", args(&i), nil, "bad verb"},
+	{"%d %d %d", "23 18", args(&i, &j), args(23, 18), "too few operands"},
+	{"%d %d", "23 18 27", args(&i, &j, &k), args(23, 18), "too many operands"},
+	{"%c", "\u0100", args(&int8Val), nil, "overflow"},
+	{"X%d", "10X", args(&intVal), nil, "input does not match format"},
+	{"%d%", "42%", args(&intVal), args(42), "missing verb: % at end of format string"},
+	{"%d% ", "42%", args(&intVal), args(42), "too few operands for format '% '"}, // Slightly odd error, but correct.
+	{"%%%d", "xxx 42", args(&intVal), args(42), "missing literal %"},
+	{"%%%d", "x42", args(&intVal), args(42), "missing literal %"},
+	{"%%%d", "42", args(&intVal), args(42), "missing literal %"},
+
+	// Bad UTF-8: should see every byte.
+	{"%c%c%c", "\xc2X\xc2", args(&r1, &r2, &r3), args(utf8.RuneError, 'X', utf8.RuneError), ""},
+
+	// Fixed bugs
+	{"%v%v", "FALSE23", args(&truth, &i), args(false, 23), ""},
+}
+
+var readers = []struct {
+	name string
+	f    func(string) io.Reader
+}{
+	{"StringReader", func(s string) io.Reader {
+		return strings.NewReader(s)
+	}},
+	{"ReaderOnly", func(s string) io.Reader {
+		return struct{ io.Reader }{strings.NewReader(s)}
+	}},
+	{"OneByteReader", func(s string) io.Reader {
+		return iotest.OneByteReader(strings.NewReader(s))
+	}},
+	{"DataErrReader", func(s string) io.Reader {
+		return iotest.DataErrReader(strings.NewReader(s))
+	}},
+}
+
+func testScan(t *testing.T, f func(string) io.Reader, scan func(r io.Reader, a ...any) (int, error)) {
+	for _, test := range scanTests {
+		r := f(test.text)
+		n, err := scan(r, test.in)
+		if err != nil {
+			m := ""
+			if n > 0 {
+				m = Sprintf(" (%d fields ok)", n)
+			}
+			t.Errorf("got error scanning %q: %s%s", test.text, err, m)
+			continue
+		}
+		if n != 1 {
+			t.Errorf("count error on entry %q: got %d", test.text, n)
+			continue
+		}
+		// The incoming value may be a pointer
+		v := reflect.ValueOf(test.in)
+		if p := v; p.Kind() == reflect.Pointer {
+			v = p.Elem()
+		}
+		val := v.Interface()
+		if !reflect.DeepEqual(val, test.out) {
+			t.Errorf("scanning %q: expected %#v got %#v, type %T", test.text, test.out, val, val)
+		}
+	}
+}
+
+func TestScan(t *testing.T) {
+	for _, r := range readers {
+		t.Run(r.name, func(t *testing.T) {
+			testScan(t, r.f, Fscan)
+		})
+	}
+}
+
+func TestScanln(t *testing.T) {
+	for _, r := range readers {
+		t.Run(r.name, func(t *testing.T) {
+			testScan(t, r.f, Fscanln)
+		})
+	}
+}
+
+func TestScanf(t *testing.T) {
+	for _, test := range scanfTests {
+		n, err := Sscanf(test.text, test.format, test.in)
+		if err != nil {
+			if test.out != nil {
+				t.Errorf("Sscanf(%q, %q): unexpected error: %v", test.text, test.format, err)
+			}
+			continue
+		}
+		if test.out == nil {
+			t.Errorf("Sscanf(%q, %q): unexpected success", test.text, test.format)
+			continue
+		}
+		if n != 1 {
+			t.Errorf("Sscanf(%q, %q): parsed %d field, want 1", test.text, test.format, n)
+			continue
+		}
+		// The incoming value may be a pointer
+		v := reflect.ValueOf(test.in)
+		if p := v; p.Kind() == reflect.Pointer {
+			v = p.Elem()
+		}
+		val := v.Interface()
+		if !reflect.DeepEqual(val, test.out) {
+			t.Errorf("Sscanf(%q, %q): parsed value %T(%#v), want %T(%#v)", test.text, test.format, val, val, test.out, test.out)
+		}
+	}
+}
+
+func TestScanOverflow(t *testing.T) {
+	// different machines and different types report errors with different strings.
+	re := regexp.MustCompile("overflow|too large|out of range|not representable")
+	for _, test := range overflowTests {
+		_, err := Sscan(test.text, test.in)
+		if err == nil {
+			t.Errorf("expected overflow scanning %q", test.text)
+			continue
+		}
+		if !re.MatchString(err.Error()) {
+			t.Errorf("expected overflow error scanning %q: %s", test.text, err)
+		}
+	}
+}
+
+func verifyNaN(str string, t *testing.T) {
+	var f float64
+	var f32 float32
+	var f64 float64
+	text := str + " " + str + " " + str
+	n, err := Fscan(strings.NewReader(text), &f, &f32, &f64)
+	if err != nil {
+		t.Errorf("got error scanning %q: %s", text, err)
+	}
+	if n != 3 {
+		t.Errorf("count error scanning %q: got %d", text, n)
+	}
+	if !math.IsNaN(float64(f)) || !math.IsNaN(float64(f32)) || !math.IsNaN(f64) {
+		t.Errorf("didn't get NaNs scanning %q: got %g %g %g", text, f, f32, f64)
+	}
+}
+
+func TestNaN(t *testing.T) {
+	for _, s := range []string{"nan", "NAN", "NaN"} {
+		verifyNaN(s, t)
+	}
+}
+
+func verifyInf(str string, t *testing.T) {
+	var f float64
+	var f32 float32
+	var f64 float64
+	text := str + " " + str + " " + str
+	n, err := Fscan(strings.NewReader(text), &f, &f32, &f64)
+	if err != nil {
+		t.Errorf("got error scanning %q: %s", text, err)
+	}
+	if n != 3 {
+		t.Errorf("count error scanning %q: got %d", text, n)
+	}
+	sign := 1
+	if str[0] == '-' {
+		sign = -1
+	}
+	if !math.IsInf(float64(f), sign) || !math.IsInf(float64(f32), sign) || !math.IsInf(f64, sign) {
+		t.Errorf("didn't get right Infs scanning %q: got %g %g %g", text, f, f32, f64)
+	}
+}
+
+func TestInf(t *testing.T) {
+	for _, s := range []string{"inf", "+inf", "-inf", "INF", "-INF", "+INF", "Inf", "-Inf", "+Inf"} {
+		verifyInf(s, t)
+	}
+}
+
+func testScanfMulti(t *testing.T, f func(string) io.Reader) {
+	sliceType := reflect.TypeOf(make([]any, 1))
+	for _, test := range multiTests {
+		r := f(test.text)
+		n, err := Fscanf(r, test.format, test.in...)
+		if err != nil {
+			if test.err == "" {
+				t.Errorf("got error scanning (%q, %q): %q", test.format, test.text, err)
+			} else if !strings.Contains(err.Error(), test.err) {
+				t.Errorf("got wrong error scanning (%q, %q): %q; expected %q", test.format, test.text, err, test.err)
+			}
+			continue
+		}
+		if test.err != "" {
+			t.Errorf("expected error %q error scanning (%q, %q)", test.err, test.format, test.text)
+		}
+		if n != len(test.out) {
+			t.Errorf("count error on entry (%q, %q): expected %d got %d", test.format, test.text, len(test.out), n)
+			continue
+		}
+		// Convert the slice of pointers into a slice of values
+		resultVal := reflect.MakeSlice(sliceType, n, n)
+		for i := 0; i < n; i++ {
+			v := reflect.ValueOf(test.in[i]).Elem()
+			resultVal.Index(i).Set(v)
+		}
+		result := resultVal.Interface()
+		if !reflect.DeepEqual(result, test.out) {
+			t.Errorf("scanning (%q, %q): expected %#v got %#v", test.format, test.text, test.out, result)
+		}
+	}
+}
+
+func TestScanfMulti(t *testing.T) {
+	for _, r := range readers {
+		t.Run(r.name, func(t *testing.T) {
+			testScanfMulti(t, r.f)
+		})
+	}
+}
+
+func TestScanMultiple(t *testing.T) {
+	var a int
+	var s string
+	n, err := Sscan("123abc", &a, &s)
+	if n != 2 {
+		t.Errorf("Sscan count error: expected 2: got %d", n)
+	}
+	if err != nil {
+		t.Errorf("Sscan expected no error; got %s", err)
+	}
+	if a != 123 || s != "abc" {
+		t.Errorf("Sscan wrong values: got (%d %q) expected (123 \"abc\")", a, s)
+	}
+	n, err = Sscan("asdf", &s, &a)
+	if n != 1 {
+		t.Errorf("Sscan count error: expected 1: got %d", n)
+	}
+	if err == nil {
+		t.Errorf("Sscan expected error; got none: %s", err)
+	}
+	if s != "asdf" {
+		t.Errorf("Sscan wrong values: got %q expected \"asdf\"", s)
+	}
+}
+
+// Empty strings are not valid input when scanning a string.
+func TestScanEmpty(t *testing.T) {
+	var s1, s2 string
+	n, err := Sscan("abc", &s1, &s2)
+	if n != 1 {
+		t.Errorf("Sscan count error: expected 1: got %d", n)
+	}
+	if err == nil {
+		t.Error("Sscan <one item> expected error; got none")
+	}
+	if s1 != "abc" {
+		t.Errorf("Sscan wrong values: got %q expected \"abc\"", s1)
+	}
+	n, err = Sscan("", &s1, &s2)
+	if n != 0 {
+		t.Errorf("Sscan count error: expected 0: got %d", n)
+	}
+	if err == nil {
+		t.Error("Sscan <empty> expected error; got none")
+	}
+	// Quoted empty string is OK.
+	n, err = Sscanf(`""`, "%q", &s1)
+	if n != 1 {
+		t.Errorf("Sscanf count error: expected 1: got %d", n)
+	}
+	if err != nil {
+		t.Errorf("Sscanf <empty> expected no error with quoted string; got %s", err)
+	}
+}
+
+func TestScanNotPointer(t *testing.T) {
+	r := strings.NewReader("1")
+	var a int
+	_, err := Fscan(r, a)
+	if err == nil {
+		t.Error("expected error scanning non-pointer")
+	} else if !strings.Contains(err.Error(), "pointer") {
+		t.Errorf("expected pointer error scanning non-pointer, got: %s", err)
+	}
+}
+
+func TestScanlnNoNewline(t *testing.T) {
+	var a int
+	_, err := Sscanln("1 x\n", &a)
+	if err == nil {
+		t.Error("expected error scanning string missing newline")
+	} else if !strings.Contains(err.Error(), "newline") {
+		t.Errorf("expected newline error scanning string missing newline, got: %s", err)
+	}
+}
+
+func TestScanlnWithMiddleNewline(t *testing.T) {
+	r := strings.NewReader("123\n456\n")
+	var a, b int
+	_, err := Fscanln(r, &a, &b)
+	if err == nil {
+		t.Error("expected error scanning string with extra newline")
+	} else if !strings.Contains(err.Error(), "newline") {
+		t.Errorf("expected newline error scanning string with extra newline, got: %s", err)
+	}
+}
+
+// eofCounter is a special Reader that counts reads at end of file.
+type eofCounter struct {
+	reader   *strings.Reader
+	eofCount int
+}
+
+func (ec *eofCounter) Read(b []byte) (n int, err error) {
+	n, err = ec.reader.Read(b)
+	if n == 0 {
+		ec.eofCount++
+	}
+	return
+}
+
+// TestEOF verifies that when we scan, we see at most EOF once per call to a
+// Scan function, and then only when it's really an EOF.
+func TestEOF(t *testing.T) {
+	ec := &eofCounter{strings.NewReader("123\n"), 0}
+	var a int
+	n, err := Fscanln(ec, &a)
+	if err != nil {
+		t.Error("unexpected error", err)
+	}
+	if n != 1 {
+		t.Error("expected to scan one item, got", n)
+	}
+	if ec.eofCount != 0 {
+		t.Error("expected zero EOFs", ec.eofCount)
+		ec.eofCount = 0 // reset for next test
+	}
+	n, err = Fscanln(ec, &a)
+	if err == nil {
+		t.Error("expected error scanning empty string")
+	}
+	if n != 0 {
+		t.Error("expected to scan zero items, got", n)
+	}
+	if ec.eofCount != 1 {
+		t.Error("expected one EOF, got", ec.eofCount)
+	}
+}
+
+// TestEOFAtEndOfInput verifies that we see an EOF error if we run out of input.
+// This was a buglet: we used to get "expected integer".
+func TestEOFAtEndOfInput(t *testing.T) {
+	var i, j int
+	n, err := Sscanf("23", "%d %d", &i, &j)
+	if n != 1 || i != 23 {
+		t.Errorf("Sscanf expected one value of 23; got %d %d", n, i)
+	}
+	if err != io.EOF {
+		t.Errorf("Sscanf expected EOF; got %q", err)
+	}
+	n, err = Sscan("234", &i, &j)
+	if n != 1 || i != 234 {
+		t.Errorf("Sscan expected one value of 234; got %d %d", n, i)
+	}
+	if err != io.EOF {
+		t.Errorf("Sscan expected EOF; got %q", err)
+	}
+	// Trailing space is tougher.
+	n, err = Sscan("234 ", &i, &j)
+	if n != 1 || i != 234 {
+		t.Errorf("Sscan expected one value of 234; got %d %d", n, i)
+	}
+	if err != io.EOF {
+		t.Errorf("Sscan expected EOF; got %q", err)
+	}
+}
+
+var eofTests = []struct {
+	format string
+	v      any
+}{
+	{"%s", &stringVal},
+	{"%q", &stringVal},
+	{"%x", &stringVal},
+	{"%v", &stringVal},
+	{"%v", &bytesVal},
+	{"%v", &intVal},
+	{"%v", &uintVal},
+	{"%v", &boolVal},
+	{"%v", &float32Val},
+	{"%v", &complex64Val},
+	{"%v", &renamedStringVal},
+	{"%v", &renamedBytesVal},
+	{"%v", &renamedIntVal},
+	{"%v", &renamedUintVal},
+	{"%v", &renamedBoolVal},
+	{"%v", &renamedFloat32Val},
+	{"%v", &renamedComplex64Val},
+}
+
+func TestEOFAllTypes(t *testing.T) {
+	for i, test := range eofTests {
+		if _, err := Sscanf("", test.format, test.v); err != io.EOF {
+			t.Errorf("#%d: %s %T not eof on empty string: %s", i, test.format, test.v, err)
+		}
+		if _, err := Sscanf("   ", test.format, test.v); err != io.EOF {
+			t.Errorf("#%d: %s %T not eof on trailing blanks: %s", i, test.format, test.v, err)
+		}
+	}
+}
+
+// TestUnreadRuneWithBufio verifies that, at least when using bufio, successive
+// calls to Fscan do not lose runes.
+func TestUnreadRuneWithBufio(t *testing.T) {
+	r := bufio.NewReader(strings.NewReader("123αb"))
+	var i int
+	var a string
+	n, err := Fscanf(r, "%d", &i)
+	if n != 1 || err != nil {
+		t.Errorf("reading int expected one item, no errors; got %d %q", n, err)
+	}
+	if i != 123 {
+		t.Errorf("expected 123; got %d", i)
+	}
+	n, err = Fscanf(r, "%s", &a)
+	if n != 1 || err != nil {
+		t.Errorf("reading string expected one item, no errors; got %d %q", n, err)
+	}
+	if a != "αb" {
+		t.Errorf("expected αb; got %q", a)
+	}
+}
+
+type TwoLines string
+
+// Scan attempts to read two lines into the object. Scanln should prevent this
+// because it stops at newline; Scan and Scanf should be fine.
+func (t *TwoLines) Scan(state ScanState, verb rune) error {
+	chars := make([]rune, 0, 100)
+	for nlCount := 0; nlCount < 2; {
+		c, _, err := state.ReadRune()
+		if err != nil {
+			return err
+		}
+		chars = append(chars, c)
+		if c == '\n' {
+			nlCount++
+		}
+	}
+	*t = TwoLines(string(chars))
+	return nil
+}
+
+func TestMultiLine(t *testing.T) {
+	input := "abc\ndef\n"
+	// Sscan should work
+	var tscan TwoLines
+	n, err := Sscan(input, &tscan)
+	if n != 1 {
+		t.Errorf("Sscan: expected 1 item; got %d", n)
+	}
+	if err != nil {
+		t.Errorf("Sscan: expected no error; got %s", err)
+	}
+	if string(tscan) != input {
+		t.Errorf("Sscan: expected %q; got %q", input, tscan)
+	}
+	// Sscanf should work
+	var tscanf TwoLines
+	n, err = Sscanf(input, "%s", &tscanf)
+	if n != 1 {
+		t.Errorf("Sscanf: expected 1 item; got %d", n)
+	}
+	if err != nil {
+		t.Errorf("Sscanf: expected no error; got %s", err)
+	}
+	if string(tscanf) != input {
+		t.Errorf("Sscanf: expected %q; got %q", input, tscanf)
+	}
+	// Sscanln should not work
+	var tscanln TwoLines
+	n, err = Sscanln(input, &tscanln)
+	if n != 0 {
+		t.Errorf("Sscanln: expected 0 items; got %d: %q", n, tscanln)
+	}
+	if err == nil {
+		t.Error("Sscanln: expected error; got none")
+	} else if err != io.ErrUnexpectedEOF {
+		t.Errorf("Sscanln: expected io.ErrUnexpectedEOF (ha!); got %s", err)
+	}
+}
+
+// TestLineByLineFscanf tests that Fscanf does not read past newline. Issue
+// 3481.
+func TestLineByLineFscanf(t *testing.T) {
+	r := struct{ io.Reader }{strings.NewReader("1\n2\n")}
+	var i, j int
+	n, err := Fscanf(r, "%v\n", &i)
+	if n != 1 || err != nil {
+		t.Fatalf("first read: %d %q", n, err)
+	}
+	n, err = Fscanf(r, "%v\n", &j)
+	if n != 1 || err != nil {
+		t.Fatalf("second read: %d %q", n, err)
+	}
+	if i != 1 || j != 2 {
+		t.Errorf("wrong values; wanted 1 2 got %d %d", i, j)
+	}
+}
+
+// TestScanStateCount verifies the correct byte count is returned. Issue 8512.
+
+// runeScanner implements the Scanner interface for TestScanStateCount.
+type runeScanner struct {
+	rune rune
+	size int
+}
+
+func (rs *runeScanner) Scan(state ScanState, verb rune) error {
+	r, size, err := state.ReadRune()
+	rs.rune = r
+	rs.size = size
+	return err
+}
+
+func TestScanStateCount(t *testing.T) {
+	var a, b, c runeScanner
+	n, err := Sscanf("12➂", "%c%c%c", &a, &b, &c)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != 3 {
+		t.Fatalf("expected 3 items consumed, got %d", n)
+	}
+	if a.rune != '1' || b.rune != '2' || c.rune != '➂' {
+		t.Errorf("bad scan rune: %q %q %q should be '1' '2' '➂'", a.rune, b.rune, c.rune)
+	}
+	if a.size != 1 || b.size != 1 || c.size != 3 {
+		t.Errorf("bad scan size: %q %q %q should be 1 1 3", a.size, b.size, c.size)
+	}
+}
+
+// RecursiveInt accepts a string matching %d.%d.%d....
+// and parses it into a linked list.
+// It allows us to benchmark recursive descent style scanners.
+type RecursiveInt struct {
+	i    int
+	next *RecursiveInt
+}
+
+func (r *RecursiveInt) Scan(state ScanState, verb rune) (err error) {
+	_, err = Fscan(state, &r.i)
+	if err != nil {
+		return
+	}
+	next := new(RecursiveInt)
+	_, err = Fscanf(state, ".%v", next)
+	if err != nil {
+		if err == io.ErrUnexpectedEOF {
+			err = nil
+		}
+		return
+	}
+	r.next = next
+	return
+}
+
+// scanInts performs the same scanning task as RecursiveInt.Scan
+// but without recurring through scanner, so we can compare
+// performance more directly.
+func scanInts(r *RecursiveInt, b *bytes.Buffer) (err error) {
+	r.next = nil
+	_, err = Fscan(b, &r.i)
+	if err != nil {
+		return
+	}
+	c, _, err := b.ReadRune()
+	if err != nil {
+		if err == io.EOF {
+			err = nil
+		}
+		return
+	}
+	if c != '.' {
+		return
+	}
+	next := new(RecursiveInt)
+	err = scanInts(next, b)
+	if err == nil {
+		r.next = next
+	}
+	return
+}
+
+func makeInts(n int) []byte {
+	var buf bytes.Buffer
+	Fprintf(&buf, "1")
+	for i := 1; i < n; i++ {
+		Fprintf(&buf, ".%d", i+1)
+	}
+	return buf.Bytes()
+}
+
+func TestScanInts(t *testing.T) {
+	testScanInts(t, scanInts)
+	testScanInts(t, func(r *RecursiveInt, b *bytes.Buffer) (err error) {
+		_, err = Fscan(b, r)
+		return
+	})
+}
+
+// 800 is small enough to not overflow the stack when using gccgo on a
+// platform that does not support split stack.
+const intCount = 800
+
+func testScanInts(t *testing.T, scan func(*RecursiveInt, *bytes.Buffer) error) {
+	r := new(RecursiveInt)
+	ints := makeInts(intCount)
+	buf := bytes.NewBuffer(ints)
+	err := scan(r, buf)
+	if err != nil {
+		t.Error("unexpected error", err)
+	}
+	i := 1
+	for ; r != nil; r = r.next {
+		if r.i != i {
+			t.Fatalf("bad scan: expected %d got %d", i, r.i)
+		}
+		i++
+	}
+	if i-1 != intCount {
+		t.Fatalf("bad scan count: expected %d got %d", intCount, i-1)
+	}
+}
+
+func BenchmarkScanInts(b *testing.B) {
+	b.ResetTimer()
+	ints := makeInts(intCount)
+	var r RecursiveInt
+	for i := b.N - 1; i >= 0; i-- {
+		buf := bytes.NewBuffer(ints)
+		b.StartTimer()
+		scanInts(&r, buf)
+		b.StopTimer()
+	}
+}
+
+func BenchmarkScanRecursiveInt(b *testing.B) {
+	b.ResetTimer()
+	ints := makeInts(intCount)
+	var r RecursiveInt
+	for i := b.N - 1; i >= 0; i-- {
+		buf := bytes.NewBuffer(ints)
+		b.StartTimer()
+		Fscan(buf, &r)
+		b.StopTimer()
+	}
+}
+
+func BenchmarkScanRecursiveIntReaderWrapper(b *testing.B) {
+	b.ResetTimer()
+	ints := makeInts(intCount)
+	var r RecursiveInt
+	for i := b.N - 1; i >= 0; i-- {
+		buf := struct{ io.Reader }{strings.NewReader(string(ints))}
+		b.StartTimer()
+		Fscan(buf, &r)
+		b.StopTimer()
+	}
+}
+
+// Issue 9124.
+// %x on bytes couldn't handle non-space bytes terminating the scan.
+func TestHexBytes(t *testing.T) {
+	var a, b []byte
+	n, err := Sscanf("00010203", "%x", &a)
+	if n != 1 || err != nil {
+		t.Errorf("simple: got count, err = %d, %v; expected 1, nil", n, err)
+	}
+	check := func(msg string, x []byte) {
+		if len(x) != 4 {
+			t.Errorf("%s: bad length %d", msg, len(x))
+		}
+		for i, b := range x {
+			if int(b) != i {
+				t.Errorf("%s: bad x[%d] = %x", msg, i, x[i])
+			}
+		}
+	}
+	check("simple", a)
+	a = nil
+
+	n, err = Sscanf("00010203 00010203", "%x %x", &a, &b)
+	if n != 2 || err != nil {
+		t.Errorf("simple pair: got count, err = %d, %v; expected 2, nil", n, err)
+	}
+	check("simple pair a", a)
+	check("simple pair b", b)
+	a = nil
+	b = nil
+
+	n, err = Sscanf("00010203:", "%x", &a)
+	if n != 1 || err != nil {
+		t.Errorf("colon: got count, err = %d, %v; expected 1, nil", n, err)
+	}
+	check("colon", a)
+	a = nil
+
+	n, err = Sscanf("00010203:00010203", "%x:%x", &a, &b)
+	if n != 2 || err != nil {
+		t.Errorf("colon pair: got count, err = %d, %v; expected 2, nil", n, err)
+	}
+	check("colon pair a", a)
+	check("colon pair b", b)
+	a = nil
+	b = nil
+
+	// This one fails because there is a hex byte after the data,
+	// that is, an odd number of hex input bytes.
+	n, err = Sscanf("000102034:", "%x", &a)
+	if n != 0 || err == nil {
+		t.Errorf("odd count: got count, err = %d, %v; expected 0, error", n, err)
+	}
+}
+
+func TestScanNewlinesAreSpaces(t *testing.T) {
+	var a, b int
+	var tests = []struct {
+		name  string
+		text  string
+		count int
+	}{
+		{"newlines", "1\n2\n", 2},
+		{"no final newline", "1\n2", 2},
+		{"newlines with spaces ", "1  \n  2  \n", 2},
+		{"no final newline with spaces", "1  \n  2", 2},
+	}
+	for _, test := range tests {
+		n, err := Sscan(test.text, &a, &b)
+		if n != test.count {
+			t.Errorf("%s: expected to scan %d item(s), scanned %d", test.name, test.count, n)
+		}
+		if err != nil {
+			t.Errorf("%s: unexpected error: %s", test.name, err)
+		}
+	}
+}
+
+func TestScanlnNewlinesTerminate(t *testing.T) {
+	var a, b int
+	var tests = []struct {
+		name  string
+		text  string
+		count int
+		ok    bool
+	}{
+		{"one line one item", "1\n", 1, false},
+		{"one line two items with spaces ", "   1 2    \n", 2, true},
+		{"one line two items no newline", "   1 2", 2, true},
+		{"two lines two items", "1\n2\n", 1, false},
+	}
+	for _, test := range tests {
+		n, err := Sscanln(test.text, &a, &b)
+		if n != test.count {
+			t.Errorf("%s: expected to scan %d item(s), scanned %d", test.name, test.count, n)
+		}
+		if test.ok && err != nil {
+			t.Errorf("%s: unexpected error: %s", test.name, err)
+		}
+		if !test.ok && err == nil {
+			t.Errorf("%s: expected error; got none", test.name)
+		}
+	}
+}
+
+func TestScanfNewlineMatchFormat(t *testing.T) {
+	var a, b int
+	var tests = []struct {
+		name   string
+		text   string
+		format string
+		count  int
+		ok     bool
+	}{
+		{"newline in both", "1\n2", "%d\n%d\n", 2, true},
+		{"newline in input", "1\n2", "%d %d", 1, false},
+		{"space-newline in input", "1 \n2", "%d %d", 1, false},
+		{"newline in format", "1 2", "%d\n%d", 1, false},
+		{"space-newline in format", "1 2", "%d \n%d", 1, false},
+		{"space-newline in both", "1 \n2", "%d \n%d", 2, true},
+		{"extra space in format", "1\n2", "%d\n %d", 2, true},
+		{"two extra spaces in format", "1\n2", "%d \n %d", 2, true},
+		{"space vs newline 0000", "1\n2", "%d\n%d", 2, true},
+		{"space vs newline 0001", "1\n2", "%d\n %d", 2, true},
+		{"space vs newline 0010", "1\n2", "%d \n%d", 2, true},
+		{"space vs newline 0011", "1\n2", "%d \n %d", 2, true},
+		{"space vs newline 0100", "1\n 2", "%d\n%d", 2, true},
+		{"space vs newline 0101", "1\n 2", "%d\n%d ", 2, true},
+		{"space vs newline 0110", "1\n 2", "%d \n%d", 2, true},
+		{"space vs newline 0111", "1\n 2", "%d \n %d", 2, true},
+		{"space vs newline 1000", "1 \n2", "%d\n%d", 2, true},
+		{"space vs newline 1001", "1 \n2", "%d\n %d", 2, true},
+		{"space vs newline 1010", "1 \n2", "%d \n%d", 2, true},
+		{"space vs newline 1011", "1 \n2", "%d \n %d", 2, true},
+		{"space vs newline 1100", "1 \n 2", "%d\n%d", 2, true},
+		{"space vs newline 1101", "1 \n 2", "%d\n %d", 2, true},
+		{"space vs newline 1110", "1 \n 2", "%d \n%d", 2, true},
+		{"space vs newline 1111", "1 \n 2", "%d \n %d", 2, true},
+		{"space vs newline no-percent 0000", "1\n2", "1\n2", 0, true},
+		{"space vs newline no-percent 0001", "1\n2", "1\n 2", 0, true},
+		{"space vs newline no-percent 0010", "1\n2", "1 \n2", 0, true},
+		{"space vs newline no-percent 0011", "1\n2", "1 \n 2", 0, true},
+		{"space vs newline no-percent 0100", "1\n 2", "1\n2", 0, false},  // fails: space after nl in input but not pattern
+		{"space vs newline no-percent 0101", "1\n 2", "1\n2 ", 0, false}, // fails: space after nl in input but not pattern
+		{"space vs newline no-percent 0110", "1\n 2", "1 \n2", 0, false}, // fails: space after nl in input but not pattern
+		{"space vs newline no-percent 0111", "1\n 2", "1 \n 2", 0, true},
+		{"space vs newline no-percent 1000", "1 \n2", "1\n2", 0, true},
+		{"space vs newline no-percent 1001", "1 \n2", "1\n 2", 0, true},
+		{"space vs newline no-percent 1010", "1 \n2", "1 \n2", 0, true},
+		{"space vs newline no-percent 1011", "1 \n2", "1 \n 2", 0, true},
+		{"space vs newline no-percent 1100", "1 \n 2", "1\n2", 0, false}, // fails: space after nl in input but not pattern
+		{"space vs newline no-percent 1101", "1 \n 2", "1\n 2", 0, true},
+		{"space vs newline no-percent 1110", "1 \n 2", "1 \n2", 0, false}, // fails: space after nl in input but not pattern
+		{"space vs newline no-percent 1111", "1 \n 2", "1 \n 2", 0, true},
+	}
+	for _, test := range tests {
+		var n int
+		var err error
+		if strings.Contains(test.format, "%") {
+			n, err = Sscanf(test.text, test.format, &a, &b)
+		} else {
+			n, err = Sscanf(test.text, test.format)
+		}
+		if n != test.count {
+			t.Errorf("%s: expected to scan %d item(s), scanned %d", test.name, test.count, n)
+		}
+		if test.ok && err != nil {
+			t.Errorf("%s: unexpected error: %s", test.name, err)
+		}
+		if !test.ok && err == nil {
+			t.Errorf("%s: expected error; got none", test.name)
+		}
+	}
+}
+
+// Test for issue 12090: Was unreading at EOF, double-scanning a byte.
+
+type hexBytes [2]byte
+
+func (h *hexBytes) Scan(ss ScanState, verb rune) error {
+	var b []byte
+	_, err := Fscanf(ss, "%4x", &b)
+	if err != nil {
+		panic(err) // Really shouldn't happen.
+	}
+	copy((*h)[:], b)
+	return err
+}
+
+func TestHexByte(t *testing.T) {
+	var h hexBytes
+	n, err := Sscanln("0123\n", &h)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != 1 {
+		t.Fatalf("expected 1 item; scanned %d", n)
+	}
+	if h[0] != 0x01 || h[1] != 0x23 {
+		t.Fatalf("expected 0123 got %x", h)
+	}
+}