libgo: update to Go1.17rc2

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/341629

21 files changed, 834 insertions, 451 deletions

diff --git a/libgo/go/encoding/asn1/asn1.go b/libgo/go/encoding/asn1/asn1.go
index f9b9cb4..cffc06d 100644
--- a/libgo/go/encoding/asn1/asn1.go
+++ b/libgo/go/encoding/asn1/asn1.go
@@ -914,7 +914,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		structType := fieldType
 
 		for i := 0; i < structType.NumField(); i++ {
-			if structType.Field(i).PkgPath != "" {
+			if !structType.Field(i).IsExported() {
 				err = StructuralError{"struct contains unexported fields"}
 				return
 			}
diff --git a/libgo/go/encoding/asn1/marshal.go b/libgo/go/encoding/asn1/marshal.go
index 0d34d5a..5b4d786 100644
--- a/libgo/go/encoding/asn1/marshal.go
+++ b/libgo/go/encoding/asn1/marshal.go
@@ -488,7 +488,7 @@ func makeBody(value reflect.Value, params fieldParameters) (e encoder, err error
 		t := v.Type()
 
 		for i := 0; i < t.NumField(); i++ {
-			if t.Field(i).PkgPath != "" {
+			if !t.Field(i).IsExported() {
 				return nil, StructuralError{"struct contains unexported fields"}
 			}
 		}
diff --git a/libgo/go/encoding/asn1/marshal_test.go b/libgo/go/encoding/asn1/marshal_test.go
index e3a7d8f..f0217ba 100644
--- a/libgo/go/encoding/asn1/marshal_test.go
+++ b/libgo/go/encoding/asn1/marshal_test.go
@@ -306,7 +306,7 @@ func TestIssue11130(t *testing.T) {
 		return
 	}
 	if !reflect.DeepEqual(v, v1) {
-		t.Errorf("got: %#v data=%q , want : %#v data=%q\n ", v1, data1, v, data)
+		t.Errorf("got: %#v data=%q, want : %#v data=%q\n ", v1, data1, v, data)
 	}
 }
 
diff --git a/libgo/go/encoding/binary/varint.go b/libgo/go/encoding/binary/varint.go
index 1fa325d..8fe20b5 100644
--- a/libgo/go/encoding/binary/varint.go
+++ b/libgo/go/encoding/binary/varint.go
@@ -61,8 +61,13 @@ func Uvarint(buf []byte) (uint64, int) {
 	var x uint64
 	var s uint
 	for i, b := range buf {
+		if i == MaxVarintLen64 {
+			// Catch byte reads past MaxVarintLen64.
+			// See issue https://golang.org/issues/41185
+			return 0, -(i + 1) // overflow
+		}
 		if b < 0x80 {
-			if i >= MaxVarintLen64 || i == MaxVarintLen64-1 && b > 1 {
+			if i == MaxVarintLen64-1 && b > 1 {
 				return 0, -(i + 1) // overflow
 			}
 			return x | uint64(b)<<s, i + 1
diff --git a/libgo/go/encoding/binary/varint_test.go b/libgo/go/encoding/binary/varint_test.go
index 6ef4c99..d025a67 100644
--- a/libgo/go/encoding/binary/varint_test.go
+++ b/libgo/go/encoding/binary/varint_test.go
@@ -7,6 +7,7 @@ package binary
 import (
 	"bytes"
 	"io"
+	"math"
 	"testing"
 )
 
@@ -121,10 +122,66 @@ func TestBufferTooSmall(t *testing.T) {
 	}
 }
 
+// Ensure that we catch overflows of bytes going past MaxVarintLen64.
+// See issue https://golang.org/issues/41185
+func TestBufferTooBigWithOverflow(t *testing.T) {
+	tests := []struct {
+		in        []byte
+		name      string
+		wantN     int
+		wantValue uint64
+	}{
+		{
+			name: "invalid: 1000 bytes",
+			in: func() []byte {
+				b := make([]byte, 1000)
+				for i := range b {
+					b[i] = 0xff
+				}
+				b[999] = 0
+				return b
+			}(),
+			wantN:     -11,
+			wantValue: 0,
+		},
+		{
+			name:      "valid: math.MaxUint64-40",
+			in:        []byte{0xd7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01},
+			wantValue: math.MaxUint64 - 40,
+			wantN:     10,
+		},
+		{
+			name:      "invalid: with more than MaxVarintLen64 bytes",
+			in:        []byte{0xd7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01},
+			wantN:     -11,
+			wantValue: 0,
+		},
+		{
+			name:      "invalid: 10th byte",
+			in:        []byte{0xd7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f},
+			wantN:     -10,
+			wantValue: 0,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			value, n := Uvarint(tt.in)
+			if g, w := n, tt.wantN; g != w {
+				t.Errorf("bytes returned=%d, want=%d", g, w)
+			}
+			if g, w := value, tt.wantValue; g != w {
+				t.Errorf("value=%d, want=%d", g, w)
+			}
+		})
+	}
+}
+
 func testOverflow(t *testing.T, buf []byte, x0 uint64, n0 int, err0 error) {
 	x, n := Uvarint(buf)
 	if x != 0 || n != n0 {
-		t.Errorf("Uvarint(%v): got x = %d, n = %d; want 0, %d", buf, x, n, n0)
+		t.Errorf("Uvarint(% X): got x = %d, n = %d; want 0, %d", buf, x, n, n0)
 	}
 
 	r := bytes.NewReader(buf)
@@ -140,8 +197,8 @@ func testOverflow(t *testing.T, buf []byte, x0 uint64, n0 int, err0 error) {
 
 func TestOverflow(t *testing.T) {
 	testOverflow(t, []byte{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x2}, 0, -10, overflow)
-	testOverflow(t, []byte{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x1, 0, 0}, 0, -13, overflow)
-	testOverflow(t, []byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}, 1<<64-1, 0, overflow) // 11 bytes, should overflow
+	testOverflow(t, []byte{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x1, 0, 0}, 0, -11, overflow)
+	testOverflow(t, []byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}, 1<<64-1, -11, overflow) // 11 bytes, should overflow
 }
 
 func TestNonCanonicalZero(t *testing.T) {
diff --git a/libgo/go/encoding/csv/fuzz.go b/libgo/go/encoding/csv/fuzz.go
index 8be21d5..a03fa83 100644
--- a/libgo/go/encoding/csv/fuzz.go
+++ b/libgo/go/encoding/csv/fuzz.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build gofuzz
 // +build gofuzz
 
 package csv
diff --git a/libgo/go/encoding/csv/reader.go b/libgo/go/encoding/csv/reader.go
index c40aa50..f860f4f 100644
--- a/libgo/go/encoding/csv/reader.go
+++ b/libgo/go/encoding/csv/reader.go
@@ -66,7 +66,7 @@ import (
 type ParseError struct {
 	StartLine int   // Line where the record starts
 	Line      int   // Line where the error occurred
-	Column    int   // Column (rune index) where the error occurred
+	Column    int   // Column (1-based byte index) where the error occurred
 	Err       error // The actual error
 }
 
@@ -162,6 +162,10 @@ type Reader struct {
 	// The i'th field ends at offset fieldIndexes[i] in recordBuffer.
 	fieldIndexes []int
 
+	// fieldPositions is an index of field positions for the
+	// last record returned by Read.
+	fieldPositions []position
+
 	// lastRecord is a record cache and only used when ReuseRecord == true.
 	lastRecord []string
 }
@@ -192,6 +196,25 @@ func (r *Reader) Read() (record []string, err error) {
 	return record, err
 }
 
+// FieldPos returns the line and column corresponding to
+// the start of the field with the given index in the slice most recently
+// returned by Read. Numbering of lines and columns starts at 1;
+// columns are counted in bytes, not runes.
+//
+// If this is called with an out-of-bounds index, it panics.
+func (r *Reader) FieldPos(field int) (line, column int) {
+	if field < 0 || field >= len(r.fieldPositions) {
+		panic("out of range index passed to FieldPos")
+	}
+	p := &r.fieldPositions[field]
+	return p.line, p.col
+}
+
+// pos holds the position of a field in the current line.
+type position struct {
+	line, col int
+}
+
 // ReadAll reads all the remaining records from r.
 // Each record is a slice of fields.
 // A successful call returns err == nil, not err == io.EOF. Because ReadAll is
@@ -260,7 +283,7 @@ func (r *Reader) readRecord(dst []string) ([]string, error) {
 	}
 
 	// Read line (automatically skipping past empty lines and any comments).
-	var line, fullLine []byte
+	var line []byte
 	var errRead error
 	for errRead == nil {
 		line, errRead = r.readLine()
@@ -272,7 +295,6 @@ func (r *Reader) readRecord(dst []string) ([]string, error) {
 			line = nil
 			continue // Skip empty lines
 		}
-		fullLine = line
 		break
 	}
 	if errRead == io.EOF {
@@ -286,10 +308,20 @@ func (r *Reader) readRecord(dst []string) ([]string, error) {
 	recLine := r.numLine // Starting line for record
 	r.recordBuffer = r.recordBuffer[:0]
 	r.fieldIndexes = r.fieldIndexes[:0]
+	r.fieldPositions = r.fieldPositions[:0]
+	pos := position{line: r.numLine, col: 1}
 parseField:
 	for {
 		if r.TrimLeadingSpace {
-			line = bytes.TrimLeftFunc(line, unicode.IsSpace)
+			i := bytes.IndexFunc(line, func(r rune) bool {
+				return !unicode.IsSpace(r)
+			})
+			if i < 0 {
+				i = len(line)
+				pos.col -= lengthNL(line)
+			}
+			line = line[i:]
+			pos.col += i
 		}
 		if len(line) == 0 || line[0] != '"' {
 			// Non-quoted string field
@@ -303,48 +335,56 @@ parseField:
 			// Check to make sure a quote does not appear in field.
 			if !r.LazyQuotes {
 				if j := bytes.IndexByte(field, '"'); j >= 0 {
-					col := utf8.RuneCount(fullLine[:len(fullLine)-len(line[j:])])
+					col := pos.col + j
 					err = &ParseError{StartLine: recLine, Line: r.numLine, Column: col, Err: ErrBareQuote}
 					break parseField
 				}
 			}
 			r.recordBuffer = append(r.recordBuffer, field...)
 			r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+			r.fieldPositions = append(r.fieldPositions, pos)
 			if i >= 0 {
 				line = line[i+commaLen:]
+				pos.col += i + commaLen
 				continue parseField
 			}
 			break parseField
 		} else {
 			// Quoted string field
+			fieldPos := pos
 			line = line[quoteLen:]
+			pos.col += quoteLen
 			for {
 				i := bytes.IndexByte(line, '"')
 				if i >= 0 {
 					// Hit next quote.
 					r.recordBuffer = append(r.recordBuffer, line[:i]...)
 					line = line[i+quoteLen:]
+					pos.col += i + quoteLen
 					switch rn := nextRune(line); {
 					case rn == '"':
 						// `""` sequence (append quote).
 						r.recordBuffer = append(r.recordBuffer, '"')
 						line = line[quoteLen:]
+						pos.col += quoteLen
 					case rn == r.Comma:
 						// `",` sequence (end of field).
 						line = line[commaLen:]
+						pos.col += commaLen
 						r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+						r.fieldPositions = append(r.fieldPositions, fieldPos)
 						continue parseField
 					case lengthNL(line) == len(line):
 						// `"\n` sequence (end of line).
 						r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+						r.fieldPositions = append(r.fieldPositions, fieldPos)
 						break parseField
 					case r.LazyQuotes:
 						// `"` sequence (bare quote).
 						r.recordBuffer = append(r.recordBuffer, '"')
 					default:
 						// `"*` sequence (invalid non-escaped quote).
-						col := utf8.RuneCount(fullLine[:len(fullLine)-len(line)-quoteLen])
-						err = &ParseError{StartLine: recLine, Line: r.numLine, Column: col, Err: ErrQuote}
+						err = &ParseError{StartLine: recLine, Line: r.numLine, Column: pos.col - quoteLen, Err: ErrQuote}
 						break parseField
 					}
 				} else if len(line) > 0 {
@@ -353,19 +393,23 @@ parseField:
 					if errRead != nil {
 						break parseField
 					}
+					pos.col += len(line)
 					line, errRead = r.readLine()
+					if len(line) > 0 {
+						pos.line++
+						pos.col = 1
+					}
 					if errRead == io.EOF {
 						errRead = nil
 					}
-					fullLine = line
 				} else {
 					// Abrupt end of file (EOF or error).
 					if !r.LazyQuotes && errRead == nil {
-						col := utf8.RuneCount(fullLine)
-						err = &ParseError{StartLine: recLine, Line: r.numLine, Column: col, Err: ErrQuote}
+						err = &ParseError{StartLine: recLine, Line: pos.line, Column: pos.col, Err: ErrQuote}
 						break parseField
 					}
 					r.fieldIndexes = append(r.fieldIndexes, len(r.recordBuffer))
+					r.fieldPositions = append(r.fieldPositions, fieldPos)
 					break parseField
 				}
 			}
@@ -392,7 +436,12 @@ parseField:
 	// Check or update the expected fields per record.
 	if r.FieldsPerRecord > 0 {
 		if len(dst) != r.FieldsPerRecord && err == nil {
-			err = &ParseError{StartLine: recLine, Line: recLine, Err: ErrFieldCount}
+			err = &ParseError{
+				StartLine: recLine,
+				Line:      recLine,
+				Column:    1,
+				Err:       ErrFieldCount,
+			}
 		}
 	} else if r.FieldsPerRecord == 0 {
 		r.FieldsPerRecord = len(dst)
diff --git a/libgo/go/encoding/csv/reader_test.go b/libgo/go/encoding/csv/reader_test.go
index 5121791..abe3fdf 100644
--- a/libgo/go/encoding/csv/reader_test.go
+++ b/libgo/go/encoding/csv/reader_test.go
@@ -5,6 +5,8 @@
 package csv
 
 import (
+	"errors"
+	"fmt"
 	"io"
 	"reflect"
 	"strings"
@@ -12,405 +14,544 @@ import (
 	"unicode/utf8"
 )
 
-func TestRead(t *testing.T) {
-	tests := []struct {
-		Name   string
-		Input  string
-		Output [][]string
-		Error  error
+type readTest struct {
+	Name      string
+	Input     string
+	Output    [][]string
+	Positions [][][2]int
+	Errors    []error
+
+	// These fields are copied into the Reader
+	Comma              rune
+	Comment            rune
+	UseFieldsPerRecord bool // false (default) means FieldsPerRecord is -1
+	FieldsPerRecord    int
+	LazyQuotes         bool
+	TrimLeadingSpace   bool
+	ReuseRecord        bool
+}
 
-		// These fields are copied into the Reader
-		Comma              rune
-		Comment            rune
-		UseFieldsPerRecord bool // false (default) means FieldsPerRecord is -1
-		FieldsPerRecord    int
-		LazyQuotes         bool
-		TrimLeadingSpace   bool
-		ReuseRecord        bool
-	}{{
-		Name:   "Simple",
-		Input:  "a,b,c\n",
-		Output: [][]string{{"a", "b", "c"}},
-	}, {
-		Name:   "CRLF",
-		Input:  "a,b\r\nc,d\r\n",
-		Output: [][]string{{"a", "b"}, {"c", "d"}},
-	}, {
-		Name:   "BareCR",
-		Input:  "a,b\rc,d\r\n",
-		Output: [][]string{{"a", "b\rc", "d"}},
-	}, {
-		Name: "RFC4180test",
-		Input: `#field1,field2,field3
-"aaa","bb
-b","ccc"
-"a,a","b""bb","ccc"
-zzz,yyy,xxx
+// In these tests, the §, ¶ and ∑ characters in readTest.Input are used to denote
+// the start of a field, a record boundary and the position of an error respectively.
+// They are removed before parsing and are used to verify the position
+// information reported by FieldPos.
+
+var readTests = []readTest{{
+	Name:   "Simple",
+	Input:  "§a,§b,§c\n",
+	Output: [][]string{{"a", "b", "c"}},
+}, {
+	Name:   "CRLF",
+	Input:  "§a,§b\r\n¶§c,§d\r\n",
+	Output: [][]string{{"a", "b"}, {"c", "d"}},
+}, {
+	Name:   "BareCR",
+	Input:  "§a,§b\rc,§d\r\n",
+	Output: [][]string{{"a", "b\rc", "d"}},
+}, {
+	Name: "RFC4180test",
+	Input: `§#field1,§field2,§field3
+¶§"aaa",§"bb
+b",§"ccc"
+¶§"a,a",§"b""bb",§"ccc"
+¶§zzz,§yyy,§xxx
 `,
-		Output: [][]string{
-			{"#field1", "field2", "field3"},
-			{"aaa", "bb\nb", "ccc"},
-			{"a,a", `b"bb`, "ccc"},
-			{"zzz", "yyy", "xxx"},
-		},
-		UseFieldsPerRecord: true,
-		FieldsPerRecord:    0,
-	}, {
-		Name:   "NoEOLTest",
-		Input:  "a,b,c",
-		Output: [][]string{{"a", "b", "c"}},
-	}, {
-		Name:   "Semicolon",
-		Input:  "a;b;c\n",
-		Output: [][]string{{"a", "b", "c"}},
-		Comma:  ';',
-	}, {
-		Name: "MultiLine",
-		Input: `"two
-line","one line","three
+	Output: [][]string{
+		{"#field1", "field2", "field3"},
+		{"aaa", "bb\nb", "ccc"},
+		{"a,a", `b"bb`, "ccc"},
+		{"zzz", "yyy", "xxx"},
+	},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:   "NoEOLTest",
+	Input:  "§a,§b,§c",
+	Output: [][]string{{"a", "b", "c"}},
+}, {
+	Name:   "Semicolon",
+	Input:  "§a;§b;§c\n",
+	Output: [][]string{{"a", "b", "c"}},
+	Comma:  ';',
+}, {
+	Name: "MultiLine",
+	Input: `§"two
+line",§"one line",§"three
 line
 field"`,
-		Output: [][]string{{"two\nline", "one line", "three\nline\nfield"}},
-	}, {
-		Name:  "BlankLine",
-		Input: "a,b,c\n\nd,e,f\n\n",
-		Output: [][]string{
-			{"a", "b", "c"},
-			{"d", "e", "f"},
-		},
-	}, {
-		Name:  "BlankLineFieldCount",
-		Input: "a,b,c\n\nd,e,f\n\n",
-		Output: [][]string{
-			{"a", "b", "c"},
-			{"d", "e", "f"},
-		},
-		UseFieldsPerRecord: true,
-		FieldsPerRecord:    0,
-	}, {
-		Name:             "TrimSpace",
-		Input:            " a,  b,   c\n",
-		Output:           [][]string{{"a", "b", "c"}},
-		TrimLeadingSpace: true,
-	}, {
-		Name:   "LeadingSpace",
-		Input:  " a,  b,   c\n",
-		Output: [][]string{{" a", "  b", "   c"}},
-	}, {
-		Name:    "Comment",
-		Input:   "#1,2,3\na,b,c\n#comment",
-		Output:  [][]string{{"a", "b", "c"}},
-		Comment: '#',
-	}, {
-		Name:   "NoComment",
-		Input:  "#1,2,3\na,b,c",
-		Output: [][]string{{"#1", "2", "3"}, {"a", "b", "c"}},
-	}, {
-		Name:       "LazyQuotes",
-		Input:      `a "word","1"2",a","b`,
-		Output:     [][]string{{`a "word"`, `1"2`, `a"`, `b`}},
-		LazyQuotes: true,
-	}, {
-		Name:       "BareQuotes",
-		Input:      `a "word","1"2",a"`,
-		Output:     [][]string{{`a "word"`, `1"2`, `a"`}},
-		LazyQuotes: true,
-	}, {
-		Name:       "BareDoubleQuotes",
-		Input:      `a""b,c`,
-		Output:     [][]string{{`a""b`, `c`}},
-		LazyQuotes: true,
-	}, {
-		Name:  "BadDoubleQuotes",
-		Input: `a""b,c`,
-		Error: &ParseError{StartLine: 1, Line: 1, Column: 1, Err: ErrBareQuote},
-	}, {
-		Name:             "TrimQuote",
-		Input:            ` "a"," b",c`,
-		Output:           [][]string{{"a", " b", "c"}},
-		TrimLeadingSpace: true,
-	}, {
-		Name:  "BadBareQuote",
-		Input: `a "word","b"`,
-		Error: &ParseError{StartLine: 1, Line: 1, Column: 2, Err: ErrBareQuote},
-	}, {
-		Name:  "BadTrailingQuote",
-		Input: `"a word",b"`,
-		Error: &ParseError{StartLine: 1, Line: 1, Column: 10, Err: ErrBareQuote},
-	}, {
-		Name:  "ExtraneousQuote",
-		Input: `"a "word","b"`,
-		Error: &ParseError{StartLine: 1, Line: 1, Column: 3, Err: ErrQuote},
-	}, {
-		Name:               "BadFieldCount",
-		Input:              "a,b,c\nd,e",
-		Error:              &ParseError{StartLine: 2, Line: 2, Err: ErrFieldCount},
-		UseFieldsPerRecord: true,
-		FieldsPerRecord:    0,
-	}, {
-		Name:               "BadFieldCount1",
-		Input:              `a,b,c`,
-		Error:              &ParseError{StartLine: 1, Line: 1, Err: ErrFieldCount},
-		UseFieldsPerRecord: true,
-		FieldsPerRecord:    2,
-	}, {
-		Name:   "FieldCount",
-		Input:  "a,b,c\nd,e",
-		Output: [][]string{{"a", "b", "c"}, {"d", "e"}},
-	}, {
-		Name:   "TrailingCommaEOF",
-		Input:  "a,b,c,",
-		Output: [][]string{{"a", "b", "c", ""}},
-	}, {
-		Name:   "TrailingCommaEOL",
-		Input:  "a,b,c,\n",
-		Output: [][]string{{"a", "b", "c", ""}},
-	}, {
-		Name:             "TrailingCommaSpaceEOF",
-		Input:            "a,b,c, ",
-		Output:           [][]string{{"a", "b", "c", ""}},
-		TrimLeadingSpace: true,
-	}, {
-		Name:             "TrailingCommaSpaceEOL",
-		Input:            "a,b,c, \n",
-		Output:           [][]string{{"a", "b", "c", ""}},
-		TrimLeadingSpace: true,
-	}, {
-		Name:             "TrailingCommaLine3",
-		Input:            "a,b,c\nd,e,f\ng,hi,",
-		Output:           [][]string{{"a", "b", "c"}, {"d", "e", "f"}, {"g", "hi", ""}},
-		TrimLeadingSpace: true,
-	}, {
-		Name:   "NotTrailingComma3",
-		Input:  "a,b,c, \n",
-		Output: [][]string{{"a", "b", "c", " "}},
-	}, {
-		Name: "CommaFieldTest",
-		Input: `x,y,z,w
-x,y,z,
-x,y,,
-x,,,
-,,,
-"x","y","z","w"
-"x","y","z",""
-"x","y","",""
-"x","","",""
-"","","",""
+	Output: [][]string{{"two\nline", "one line", "three\nline\nfield"}},
+}, {
+	Name:  "BlankLine",
+	Input: "§a,§b,§c\n\n¶§d,§e,§f\n\n",
+	Output: [][]string{
+		{"a", "b", "c"},
+		{"d", "e", "f"},
+	},
+}, {
+	Name:  "BlankLineFieldCount",
+	Input: "§a,§b,§c\n\n¶§d,§e,§f\n\n",
+	Output: [][]string{
+		{"a", "b", "c"},
+		{"d", "e", "f"},
+	},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:             "TrimSpace",
+	Input:            " §a,  §b,   §c\n",
+	Output:           [][]string{{"a", "b", "c"}},
+	TrimLeadingSpace: true,
+}, {
+	Name:   "LeadingSpace",
+	Input:  "§ a,§  b,§   c\n",
+	Output: [][]string{{" a", "  b", "   c"}},
+}, {
+	Name:    "Comment",
+	Input:   "#1,2,3\n§a,§b,§c\n#comment",
+	Output:  [][]string{{"a", "b", "c"}},
+	Comment: '#',
+}, {
+	Name:   "NoComment",
+	Input:  "§#1,§2,§3\n¶§a,§b,§c",
+	Output: [][]string{{"#1", "2", "3"}, {"a", "b", "c"}},
+}, {
+	Name:       "LazyQuotes",
+	Input:      `§a "word",§"1"2",§a",§"b`,
+	Output:     [][]string{{`a "word"`, `1"2`, `a"`, `b`}},
+	LazyQuotes: true,
+}, {
+	Name:       "BareQuotes",
+	Input:      `§a "word",§"1"2",§a"`,
+	Output:     [][]string{{`a "word"`, `1"2`, `a"`}},
+	LazyQuotes: true,
+}, {
+	Name:       "BareDoubleQuotes",
+	Input:      `§a""b,§c`,
+	Output:     [][]string{{`a""b`, `c`}},
+	LazyQuotes: true,
+}, {
+	Name:   "BadDoubleQuotes",
+	Input:  `§a∑""b,c`,
+	Errors: []error{&ParseError{Err: ErrBareQuote}},
+}, {
+	Name:             "TrimQuote",
+	Input:            ` §"a",§" b",§c`,
+	Output:           [][]string{{"a", " b", "c"}},
+	TrimLeadingSpace: true,
+}, {
+	Name:   "BadBareQuote",
+	Input:  `§a ∑"word","b"`,
+	Errors: []error{&ParseError{Err: ErrBareQuote}},
+}, {
+	Name:   "BadTrailingQuote",
+	Input:  `§"a word",b∑"`,
+	Errors: []error{&ParseError{Err: ErrBareQuote}},
+}, {
+	Name:   "ExtraneousQuote",
+	Input:  `§"a ∑"word","b"`,
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:               "BadFieldCount",
+	Input:              "§a,§b,§c\n¶∑§d,§e",
+	Errors:             []error{nil, &ParseError{Err: ErrFieldCount}},
+	Output:             [][]string{{"a", "b", "c"}, {"d", "e"}},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:               "BadFieldCountMultiple",
+	Input:              "§a,§b,§c\n¶∑§d,§e\n¶∑§f",
+	Errors:             []error{nil, &ParseError{Err: ErrFieldCount}, &ParseError{Err: ErrFieldCount}},
+	Output:             [][]string{{"a", "b", "c"}, {"d", "e"}, {"f"}},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    0,
+}, {
+	Name:               "BadFieldCount1",
+	Input:              `§∑a,§b,§c`,
+	Errors:             []error{&ParseError{Err: ErrFieldCount}},
+	Output:             [][]string{{"a", "b", "c"}},
+	UseFieldsPerRecord: true,
+	FieldsPerRecord:    2,
+}, {
+	Name:   "FieldCount",
+	Input:  "§a,§b,§c\n¶§d,§e",
+	Output: [][]string{{"a", "b", "c"}, {"d", "e"}},
+}, {
+	Name:   "TrailingCommaEOF",
+	Input:  "§a,§b,§c,§",
+	Output: [][]string{{"a", "b", "c", ""}},
+}, {
+	Name:   "TrailingCommaEOL",
+	Input:  "§a,§b,§c,§\n",
+	Output: [][]string{{"a", "b", "c", ""}},
+}, {
+	Name:             "TrailingCommaSpaceEOF",
+	Input:            "§a,§b,§c, §",
+	Output:           [][]string{{"a", "b", "c", ""}},
+	TrimLeadingSpace: true,
+}, {
+	Name:             "TrailingCommaSpaceEOL",
+	Input:            "§a,§b,§c, §\n",
+	Output:           [][]string{{"a", "b", "c", ""}},
+	TrimLeadingSpace: true,
+}, {
+	Name:             "TrailingCommaLine3",
+	Input:            "§a,§b,§c\n¶§d,§e,§f\n¶§g,§hi,§",
+	Output:           [][]string{{"a", "b", "c"}, {"d", "e", "f"}, {"g", "hi", ""}},
+	TrimLeadingSpace: true,
+}, {
+	Name:   "NotTrailingComma3",
+	Input:  "§a,§b,§c,§ \n",
+	Output: [][]string{{"a", "b", "c", " "}},
+}, {
+	Name: "CommaFieldTest",
+	Input: `§x,§y,§z,§w
+¶§x,§y,§z,§
+¶§x,§y,§,§
+¶§x,§,§,§
+¶§,§,§,§
+¶§"x",§"y",§"z",§"w"
+¶§"x",§"y",§"z",§""
+¶§"x",§"y",§"",§""
+¶§"x",§"",§"",§""
+¶§"",§"",§"",§""
 `,
-		Output: [][]string{
-			{"x", "y", "z", "w"},
-			{"x", "y", "z", ""},
-			{"x", "y", "", ""},
-			{"x", "", "", ""},
-			{"", "", "", ""},
-			{"x", "y", "z", "w"},
-			{"x", "y", "z", ""},
-			{"x", "y", "", ""},
-			{"x", "", "", ""},
-			{"", "", "", ""},
-		},
-	}, {
-		Name:  "TrailingCommaIneffective1",
-		Input: "a,b,\nc,d,e",
-		Output: [][]string{
-			{"a", "b", ""},
-			{"c", "d", "e"},
-		},
-		TrimLeadingSpace: true,
-	}, {
-		Name:  "ReadAllReuseRecord",
-		Input: "a,b\nc,d",
-		Output: [][]string{
-			{"a", "b"},
-			{"c", "d"},
-		},
-		ReuseRecord: true,
-	}, {
-		Name:  "StartLine1", // Issue 19019
-		Input: "a,\"b\nc\"d,e",
-		Error: &ParseError{StartLine: 1, Line: 2, Column: 1, Err: ErrQuote},
-	}, {
-		Name:  "StartLine2",
-		Input: "a,b\n\"d\n\n,e",
-		Error: &ParseError{StartLine: 2, Line: 5, Column: 0, Err: ErrQuote},
-	}, {
-		Name:  "CRLFInQuotedField", // Issue 21201
-		Input: "A,\"Hello\r\nHi\",B\r\n",
-		Output: [][]string{
-			{"A", "Hello\nHi", "B"},
-		},
-	}, {
-		Name:   "BinaryBlobField", // Issue 19410
-		Input:  "x09\x41\xb4\x1c,aktau",
-		Output: [][]string{{"x09A\xb4\x1c", "aktau"}},
-	}, {
-		Name:   "TrailingCR",
-		Input:  "field1,field2\r",
-		Output: [][]string{{"field1", "field2"}},
-	}, {
-		Name:   "QuotedTrailingCR",
-		Input:  "\"field\"\r",
-		Output: [][]string{{"field"}},
-	}, {
-		Name:  "QuotedTrailingCRCR",
-		Input: "\"field\"\r\r",
-		Error: &ParseError{StartLine: 1, Line: 1, Column: 6, Err: ErrQuote},
-	}, {
-		Name:   "FieldCR",
-		Input:  "field\rfield\r",
-		Output: [][]string{{"field\rfield"}},
-	}, {
-		Name:   "FieldCRCR",
-		Input:  "field\r\rfield\r\r",
-		Output: [][]string{{"field\r\rfield\r"}},
-	}, {
-		Name:   "FieldCRCRLF",
-		Input:  "field\r\r\nfield\r\r\n",
-		Output: [][]string{{"field\r"}, {"field\r"}},
-	}, {
-		Name:   "FieldCRCRLFCR",
-		Input:  "field\r\r\n\rfield\r\r\n\r",
-		Output: [][]string{{"field\r"}, {"\rfield\r"}},
-	}, {
-		Name:   "FieldCRCRLFCRCR",
-		Input:  "field\r\r\n\r\rfield\r\r\n\r\r",
-		Output: [][]string{{"field\r"}, {"\r\rfield\r"}, {"\r"}},
-	}, {
-		Name:  "MultiFieldCRCRLFCRCR",
-		Input: "field1,field2\r\r\n\r\rfield1,field2\r\r\n\r\r,",
-		Output: [][]string{
-			{"field1", "field2\r"},
-			{"\r\rfield1", "field2\r"},
-			{"\r\r", ""},
-		},
-	}, {
-		Name:             "NonASCIICommaAndComment",
-		Input:            "a£b,c£ \td,e\n€ comment\n",
-		Output:           [][]string{{"a", "b,c", "d,e"}},
-		TrimLeadingSpace: true,
-		Comma:            '£',
-		Comment:          '€',
-	}, {
-		Name:    "NonASCIICommaAndCommentWithQuotes",
-		Input:   "a€\"  b,\"€ c\nλ comment\n",
-		Output:  [][]string{{"a", "  b,", " c"}},
-		Comma:   '€',
-		Comment: 'λ',
-	}, {
-		// λ and θ start with the same byte.
-		// This tests that the parser doesn't confuse such characters.
-		Name:    "NonASCIICommaConfusion",
-		Input:   "\"abθcd\"λefθgh",
-		Output:  [][]string{{"abθcd", "efθgh"}},
-		Comma:   'λ',
-		Comment: '€',
-	}, {
-		Name:    "NonASCIICommentConfusion",
-		Input:   "λ\nλ\nθ\nλ\n",
-		Output:  [][]string{{"λ"}, {"λ"}, {"λ"}},
-		Comment: 'θ',
-	}, {
-		Name:   "QuotedFieldMultipleLF",
-		Input:  "\"\n\n\n\n\"",
-		Output: [][]string{{"\n\n\n\n"}},
-	}, {
-		Name:  "MultipleCRLF",
-		Input: "\r\n\r\n\r\n\r\n",
-	}, {
-		// The implementation may read each line in several chunks if it doesn't fit entirely
-		// in the read buffer, so we should test the code to handle that condition.
-		Name:    "HugeLines",
-		Input:   strings.Repeat("#ignore\n", 10000) + strings.Repeat("@", 5000) + "," + strings.Repeat("*", 5000),
-		Output:  [][]string{{strings.Repeat("@", 5000), strings.Repeat("*", 5000)}},
-		Comment: '#',
-	}, {
-		Name:  "QuoteWithTrailingCRLF",
-		Input: "\"foo\"bar\"\r\n",
-		Error: &ParseError{StartLine: 1, Line: 1, Column: 4, Err: ErrQuote},
-	}, {
-		Name:       "LazyQuoteWithTrailingCRLF",
-		Input:      "\"foo\"bar\"\r\n",
-		Output:     [][]string{{`foo"bar`}},
-		LazyQuotes: true,
-	}, {
-		Name:   "DoubleQuoteWithTrailingCRLF",
-		Input:  "\"foo\"\"bar\"\r\n",
-		Output: [][]string{{`foo"bar`}},
-	}, {
-		Name:   "EvenQuotes",
-		Input:  `""""""""`,
-		Output: [][]string{{`"""`}},
-	}, {
-		Name:  "OddQuotes",
-		Input: `"""""""`,
-		Error: &ParseError{StartLine: 1, Line: 1, Column: 7, Err: ErrQuote},
-	}, {
-		Name:       "LazyOddQuotes",
-		Input:      `"""""""`,
-		Output:     [][]string{{`"""`}},
-		LazyQuotes: true,
-	}, {
-		Name:  "BadComma1",
-		Comma: '\n',
-		Error: errInvalidDelim,
-	}, {
-		Name:  "BadComma2",
-		Comma: '\r',
-		Error: errInvalidDelim,
-	}, {
-		Name:  "BadComma3",
-		Comma: '"',
-		Error: errInvalidDelim,
-	}, {
-		Name:  "BadComma4",
-		Comma: utf8.RuneError,
-		Error: errInvalidDelim,
-	}, {
-		Name:    "BadComment1",
-		Comment: '\n',
-		Error:   errInvalidDelim,
-	}, {
-		Name:    "BadComment2",
-		Comment: '\r',
-		Error:   errInvalidDelim,
-	}, {
-		Name:    "BadComment3",
-		Comment: utf8.RuneError,
-		Error:   errInvalidDelim,
-	}, {
-		Name:    "BadCommaComment",
-		Comma:   'X',
-		Comment: 'X',
-		Error:   errInvalidDelim,
-	}}
+	Output: [][]string{
+		{"x", "y", "z", "w"},
+		{"x", "y", "z", ""},
+		{"x", "y", "", ""},
+		{"x", "", "", ""},
+		{"", "", "", ""},
+		{"x", "y", "z", "w"},
+		{"x", "y", "z", ""},
+		{"x", "y", "", ""},
+		{"x", "", "", ""},
+		{"", "", "", ""},
+	},
+}, {
+	Name:  "TrailingCommaIneffective1",
+	Input: "§a,§b,§\n¶§c,§d,§e",
+	Output: [][]string{
+		{"a", "b", ""},
+		{"c", "d", "e"},
+	},
+	TrimLeadingSpace: true,
+}, {
+	Name:  "ReadAllReuseRecord",
+	Input: "§a,§b\n¶§c,§d",
+	Output: [][]string{
+		{"a", "b"},
+		{"c", "d"},
+	},
+	ReuseRecord: true,
+}, {
+	Name:   "StartLine1", // Issue 19019
+	Input:  "§a,\"b\nc∑\"d,e",
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:   "StartLine2",
+	Input:  "§a,§b\n¶§\"d\n\n,e∑",
+	Errors: []error{nil, &ParseError{Err: ErrQuote}},
+	Output: [][]string{{"a", "b"}},
+}, {
+	Name:  "CRLFInQuotedField", // Issue 21201
+	Input: "§A,§\"Hello\r\nHi\",§B\r\n",
+	Output: [][]string{
+		{"A", "Hello\nHi", "B"},
+	},
+}, {
+	Name:   "BinaryBlobField", // Issue 19410
+	Input:  "§x09\x41\xb4\x1c,§aktau",
+	Output: [][]string{{"x09A\xb4\x1c", "aktau"}},
+}, {
+	Name:   "TrailingCR",
+	Input:  "§field1,§field2\r",
+	Output: [][]string{{"field1", "field2"}},
+}, {
+	Name:   "QuotedTrailingCR",
+	Input:  "§\"field\"\r",
+	Output: [][]string{{"field"}},
+}, {
+	Name:   "QuotedTrailingCRCR",
+	Input:  "§\"field∑\"\r\r",
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:   "FieldCR",
+	Input:  "§field\rfield\r",
+	Output: [][]string{{"field\rfield"}},
+}, {
+	Name:   "FieldCRCR",
+	Input:  "§field\r\rfield\r\r",
+	Output: [][]string{{"field\r\rfield\r"}},
+}, {
+	Name:   "FieldCRCRLF",
+	Input:  "§field\r\r\n¶§field\r\r\n",
+	Output: [][]string{{"field\r"}, {"field\r"}},
+}, {
+	Name:   "FieldCRCRLFCR",
+	Input:  "§field\r\r\n¶§\rfield\r\r\n\r",
+	Output: [][]string{{"field\r"}, {"\rfield\r"}},
+}, {
+	Name:   "FieldCRCRLFCRCR",
+	Input:  "§field\r\r\n¶§\r\rfield\r\r\n¶§\r\r",
+	Output: [][]string{{"field\r"}, {"\r\rfield\r"}, {"\r"}},
+}, {
+	Name:  "MultiFieldCRCRLFCRCR",
+	Input: "§field1,§field2\r\r\n¶§\r\rfield1,§field2\r\r\n¶§\r\r,§",
+	Output: [][]string{
+		{"field1", "field2\r"},
+		{"\r\rfield1", "field2\r"},
+		{"\r\r", ""},
+	},
+}, {
+	Name:             "NonASCIICommaAndComment",
+	Input:            "§a£§b,c£ \t§d,e\n€ comment\n",
+	Output:           [][]string{{"a", "b,c", "d,e"}},
+	TrimLeadingSpace: true,
+	Comma:            '£',
+	Comment:          '€',
+}, {
+	Name:    "NonASCIICommaAndCommentWithQuotes",
+	Input:   "§a€§\"  b,\"€§ c\nλ comment\n",
+	Output:  [][]string{{"a", "  b,", " c"}},
+	Comma:   '€',
+	Comment: 'λ',
+}, {
+	// λ and θ start with the same byte.
+	// This tests that the parser doesn't confuse such characters.
+	Name:    "NonASCIICommaConfusion",
+	Input:   "§\"abθcd\"λ§efθgh",
+	Output:  [][]string{{"abθcd", "efθgh"}},
+	Comma:   'λ',
+	Comment: '€',
+}, {
+	Name:    "NonASCIICommentConfusion",
+	Input:   "§λ\n¶§λ\nθ\n¶§λ\n",
+	Output:  [][]string{{"λ"}, {"λ"}, {"λ"}},
+	Comment: 'θ',
+}, {
+	Name:   "QuotedFieldMultipleLF",
+	Input:  "§\"\n\n\n\n\"",
+	Output: [][]string{{"\n\n\n\n"}},
+}, {
+	Name:  "MultipleCRLF",
+	Input: "\r\n\r\n\r\n\r\n",
+}, {
+	// The implementation may read each line in several chunks if it doesn't fit entirely
+	// in the read buffer, so we should test the code to handle that condition.
+	Name:    "HugeLines",
+	Input:   strings.Repeat("#ignore\n", 10000) + "§" + strings.Repeat("@", 5000) + ",§" + strings.Repeat("*", 5000),
+	Output:  [][]string{{strings.Repeat("@", 5000), strings.Repeat("*", 5000)}},
+	Comment: '#',
+}, {
+	Name:   "QuoteWithTrailingCRLF",
+	Input:  "§\"foo∑\"bar\"\r\n",
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:       "LazyQuoteWithTrailingCRLF",
+	Input:      "§\"foo\"bar\"\r\n",
+	Output:     [][]string{{`foo"bar`}},
+	LazyQuotes: true,
+}, {
+	Name:   "DoubleQuoteWithTrailingCRLF",
+	Input:  "§\"foo\"\"bar\"\r\n",
+	Output: [][]string{{`foo"bar`}},
+}, {
+	Name:   "EvenQuotes",
+	Input:  `§""""""""`,
+	Output: [][]string{{`"""`}},
+}, {
+	Name:   "OddQuotes",
+	Input:  `§"""""""∑`,
+	Errors: []error{&ParseError{Err: ErrQuote}},
+}, {
+	Name:       "LazyOddQuotes",
+	Input:      `§"""""""`,
+	Output:     [][]string{{`"""`}},
+	LazyQuotes: true,
+}, {
+	Name:   "BadComma1",
+	Comma:  '\n',
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:   "BadComma2",
+	Comma:  '\r',
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:   "BadComma3",
+	Comma:  '"',
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:   "BadComma4",
+	Comma:  utf8.RuneError,
+	Errors: []error{errInvalidDelim},
+}, {
+	Name:    "BadComment1",
+	Comment: '\n',
+	Errors:  []error{errInvalidDelim},
+}, {
+	Name:    "BadComment2",
+	Comment: '\r',
+	Errors:  []error{errInvalidDelim},
+}, {
+	Name:    "BadComment3",
+	Comment: utf8.RuneError,
+	Errors:  []error{errInvalidDelim},
+}, {
+	Name:    "BadCommaComment",
+	Comma:   'X',
+	Comment: 'X',
+	Errors:  []error{errInvalidDelim},
+}}
 
-	for _, tt := range tests {
-		t.Run(tt.Name, func(t *testing.T) {
-			r := NewReader(strings.NewReader(tt.Input))
+func TestRead(t *testing.T) {
+	newReader := func(tt readTest) (*Reader, [][][2]int, map[int][2]int) {
+		positions, errPositions, input := makePositions(tt.Input)
+		r := NewReader(strings.NewReader(input))
 
-			if tt.Comma != 0 {
-				r.Comma = tt.Comma
-			}
-			r.Comment = tt.Comment
-			if tt.UseFieldsPerRecord {
-				r.FieldsPerRecord = tt.FieldsPerRecord
+		if tt.Comma != 0 {
+			r.Comma = tt.Comma
+		}
+		r.Comment = tt.Comment
+		if tt.UseFieldsPerRecord {
+			r.FieldsPerRecord = tt.FieldsPerRecord
+		} else {
+			r.FieldsPerRecord = -1
+		}
+		r.LazyQuotes = tt.LazyQuotes
+		r.TrimLeadingSpace = tt.TrimLeadingSpace
+		r.ReuseRecord = tt.ReuseRecord
+		return r, positions, errPositions
+	}
+
+	for _, tt := range readTests {
+		t.Run(tt.Name, func(t *testing.T) {
+			r, positions, errPositions := newReader(tt)
+			out, err := r.ReadAll()
+			if wantErr := firstError(tt.Errors, positions, errPositions); wantErr != nil {
+				if !reflect.DeepEqual(err, wantErr) {
+					t.Fatalf("ReadAll() error mismatch:\ngot  %v (%#v)\nwant %v (%#v)", err, err, wantErr, wantErr)
+				}
+				if out != nil {
+					t.Fatalf("ReadAll() output:\ngot  %q\nwant nil", out)
+				}
 			} else {
-				r.FieldsPerRecord = -1
+				if err != nil {
+					t.Fatalf("unexpected Readall() error: %v", err)
+				}
+				if !reflect.DeepEqual(out, tt.Output) {
+					t.Fatalf("ReadAll() output:\ngot  %q\nwant %q", out, tt.Output)
+				}
 			}
-			r.LazyQuotes = tt.LazyQuotes
-			r.TrimLeadingSpace = tt.TrimLeadingSpace
-			r.ReuseRecord = tt.ReuseRecord
 
-			out, err := r.ReadAll()
-			if !reflect.DeepEqual(err, tt.Error) {
-				t.Errorf("ReadAll() error:\ngot  %v\nwant %v", err, tt.Error)
-			} else if !reflect.DeepEqual(out, tt.Output) {
-				t.Errorf("ReadAll() output:\ngot  %q\nwant %q", out, tt.Output)
+			// Check field and error positions.
+			r, _, _ = newReader(tt)
+			for recNum := 0; ; recNum++ {
+				rec, err := r.Read()
+				var wantErr error
+				if recNum < len(tt.Errors) && tt.Errors[recNum] != nil {
+					wantErr = errorWithPosition(tt.Errors[recNum], recNum, positions, errPositions)
+				} else if recNum >= len(tt.Output) {
+					wantErr = io.EOF
+				}
+				if !reflect.DeepEqual(err, wantErr) {
+					t.Fatalf("Read() error at record %d:\ngot %v (%#v)\nwant %v (%#v)", recNum, err, err, wantErr, wantErr)
+				}
+				// ErrFieldCount is explicitly non-fatal.
+				if err != nil && !errors.Is(err, ErrFieldCount) {
+					if recNum < len(tt.Output) {
+						t.Fatalf("need more records; got %d want %d", recNum, len(tt.Output))
+					}
+					break
+				}
+				if got, want := rec, tt.Output[recNum]; !reflect.DeepEqual(got, want) {
+					t.Errorf("Read vs ReadAll mismatch;\ngot %q\nwant %q", got, want)
+				}
+				pos := positions[recNum]
+				if len(pos) != len(rec) {
+					t.Fatalf("mismatched position length at record %d", recNum)
+				}
+				for i := range rec {
+					line, col := r.FieldPos(i)
+					if got, want := [2]int{line, col}, pos[i]; got != want {
+						t.Errorf("position mismatch at record %d, field %d;\ngot %v\nwant %v", recNum, i, got, want)
+					}
+				}
 			}
 		})
 	}
 }
 
+// firstError returns the first non-nil error in errs,
+// with the position adjusted according to the error's
+// index inside positions.
+func firstError(errs []error, positions [][][2]int, errPositions map[int][2]int) error {
+	for i, err := range errs {
+		if err != nil {
+			return errorWithPosition(err, i, positions, errPositions)
+		}
+	}
+	return nil
+}
+
+func errorWithPosition(err error, recNum int, positions [][][2]int, errPositions map[int][2]int) error {
+	parseErr, ok := err.(*ParseError)
+	if !ok {
+		return err
+	}
+	if recNum >= len(positions) {
+		panic(fmt.Errorf("no positions found for error at record %d", recNum))
+	}
+	errPos, ok := errPositions[recNum]
+	if !ok {
+		panic(fmt.Errorf("no error position found for error at record %d", recNum))
+	}
+	parseErr1 := *parseErr
+	parseErr1.StartLine = positions[recNum][0][0]
+	parseErr1.Line = errPos[0]
+	parseErr1.Column = errPos[1]
+	return &parseErr1
+}
+
+// makePositions returns the expected field positions of all
+// the fields in text, the positions of any errors, and the text with the position markers
+// removed.
+//
+// The start of each field is marked with a § symbol;
+// CSV lines are separated by ¶ symbols;
+// Error positions are marked with ∑ symbols.
+func makePositions(text string) ([][][2]int, map[int][2]int, string) {
+	buf := make([]byte, 0, len(text))
+	var positions [][][2]int
+	errPositions := make(map[int][2]int)
+	line, col := 1, 1
+	recNum := 0
+
+	for len(text) > 0 {
+		r, size := utf8.DecodeRuneInString(text)
+		switch r {
+		case '\n':
+			line++
+			col = 1
+			buf = append(buf, '\n')
+		case '§':
+			if len(positions) == 0 {
+				positions = append(positions, [][2]int{})
+			}
+			positions[len(positions)-1] = append(positions[len(positions)-1], [2]int{line, col})
+		case '¶':
+			positions = append(positions, [][2]int{})
+			recNum++
+		case '∑':
+			errPositions[recNum] = [2]int{line, col}
+		default:
+			buf = append(buf, text[:size]...)
+			col += size
+		}
+		text = text[size:]
+	}
+	return positions, errPositions, string(buf)
+}
+
 // nTimes is an io.Reader which yields the string s n times.
 type nTimes struct {
 	s   string
diff --git a/libgo/go/encoding/gob/debug.go b/libgo/go/encoding/gob/debug.go
index 8f93742..5965fea 100644
--- a/libgo/go/encoding/gob/debug.go
+++ b/libgo/go/encoding/gob/debug.go
@@ -3,6 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // Delete the next line to include in the gob package.
+//go:build ignore
 // +build ignore
 
 package gob
diff --git a/libgo/go/encoding/gob/decgen.go b/libgo/go/encoding/gob/decgen.go
index 1c31e66..994be87 100644
--- a/libgo/go/encoding/gob/decgen.go
+++ b/libgo/go/encoding/gob/decgen.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 // encgen writes the helper functions for encoding. Intended to be
diff --git a/libgo/go/encoding/gob/decoder.go b/libgo/go/encoding/gob/decoder.go
index b52aabe..b476aaa 100644
--- a/libgo/go/encoding/gob/decoder.go
+++ b/libgo/go/encoding/gob/decoder.go
@@ -152,6 +152,9 @@ func (dec *Decoder) decodeTypeSequence(isInterface bool) typeId {
 		}
 		// Type definition for (-id) follows.
 		dec.recvType(-id)
+		if dec.err != nil {
+			break
+		}
 		// When decoding an interface, after a type there may be a
 		// DelimitedValue still in the buffer. Skip its count.
 		// (Alternatively, the buffer is empty and the byte count
@@ -215,7 +218,7 @@ func (dec *Decoder) DecodeValue(v reflect.Value) error {
 	return dec.err
 }
 
-// If debug.go is compiled into the program , debugFunc prints a human-readable
+// If debug.go is compiled into the program, debugFunc prints a human-readable
 // representation of the gob data read from r by calling that file's Debug function.
 // Otherwise it is nil.
 var debugFunc func(io.Reader)
diff --git a/libgo/go/encoding/gob/dump.go b/libgo/go/encoding/gob/dump.go
index 17238c9..8c0bbc4 100644
--- a/libgo/go/encoding/gob/dump.go
+++ b/libgo/go/encoding/gob/dump.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 package main
diff --git a/libgo/go/encoding/gob/encgen.go b/libgo/go/encoding/gob/encgen.go
index 409b8c9..b562da1 100644
--- a/libgo/go/encoding/gob/encgen.go
+++ b/libgo/go/encoding/gob/encgen.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 // encgen writes the helper functions for encoding. Intended to be
diff --git a/libgo/go/encoding/gob/encoder_test.go b/libgo/go/encoding/gob/encoder_test.go
index fe27749..6183646 100644
--- a/libgo/go/encoding/gob/encoder_test.go
+++ b/libgo/go/encoding/gob/encoder_test.go
@@ -1127,3 +1127,28 @@ func TestBadData(t *testing.T) {
 		}
 	}
 }
+
+func TestDecodeErrorMultipleTypes(t *testing.T) {
+	type Test struct {
+		A string
+		B int
+	}
+	var b bytes.Buffer
+	NewEncoder(&b).Encode(Test{"one", 1})
+
+	var result, result2 Test
+	dec := NewDecoder(&b)
+	err := dec.Decode(&result)
+	if err != nil {
+		t.Errorf("decode: unexpected error %v", err)
+	}
+
+	b.Reset()
+	NewEncoder(&b).Encode(Test{"two", 2})
+	err = dec.Decode(&result2)
+	if err == nil {
+		t.Errorf("decode: expected duplicate type error, got nil")
+	} else if !strings.Contains(err.Error(), "duplicate type") {
+		t.Errorf("decode: expected duplicate type error, got %s", err.Error())
+	}
+}
diff --git a/libgo/go/encoding/json/decode.go b/libgo/go/encoding/json/decode.go
index 86d8a69..a9917e7 100644
--- a/libgo/go/encoding/json/decode.go
+++ b/libgo/go/encoding/json/decode.go
@@ -200,16 +200,19 @@ func (n Number) Int64() (int64, error) {
 	return strconv.ParseInt(string(n), 10, 64)
 }
 
+// An errorContext provides context for type errors during decoding.
+type errorContext struct {
+	Struct     reflect.Type
+	FieldStack []string
+}
+
 // decodeState represents the state while decoding a JSON value.
 type decodeState struct {
-	data         []byte
-	off          int // next read offset in data
-	opcode       int // last read result
-	scan         scanner
-	errorContext struct { // provides context for type errors
-		Struct     reflect.Type
-		FieldStack []string
-	}
+	data                  []byte
+	off                   int // next read offset in data
+	opcode                int // last read result
+	scan                  scanner
+	errorContext          *errorContext
 	savedError            error
 	useNumber             bool
 	disallowUnknownFields bool
@@ -229,10 +232,11 @@ func (d *decodeState) init(data []byte) *decodeState {
 	d.data = data
 	d.off = 0
 	d.savedError = nil
-	d.errorContext.Struct = nil
-
-	// Reuse the allocated space for the FieldStack slice.
-	d.errorContext.FieldStack = d.errorContext.FieldStack[:0]
+	if d.errorContext != nil {
+		d.errorContext.Struct = nil
+		// Reuse the allocated space for the FieldStack slice.
+		d.errorContext.FieldStack = d.errorContext.FieldStack[:0]
+	}
 	return d
 }
 
@@ -246,12 +250,11 @@ func (d *decodeState) saveError(err error) {
 
 // addErrorContext returns a new error enhanced with information from d.errorContext
 func (d *decodeState) addErrorContext(err error) error {
-	if d.errorContext.Struct != nil || len(d.errorContext.FieldStack) > 0 {
+	if d.errorContext != nil && (d.errorContext.Struct != nil || len(d.errorContext.FieldStack) > 0) {
 		switch err := err.(type) {
 		case *UnmarshalTypeError:
 			err.Struct = d.errorContext.Struct.Name()
 			err.Field = strings.Join(d.errorContext.FieldStack, ".")
-			return err
 		}
 	}
 	return err
@@ -657,7 +660,10 @@ func (d *decodeState) object(v reflect.Value) error {
 	}
 
 	var mapElem reflect.Value
-	origErrorContext := d.errorContext
+	var origErrorContext errorContext
+	if d.errorContext != nil {
+		origErrorContext = *d.errorContext
+	}
 
 	for {
 		// Read opening " of string key or closing }.
@@ -732,6 +738,9 @@ func (d *decodeState) object(v reflect.Value) error {
 					}
 					subv = subv.Field(i)
 				}
+				if d.errorContext == nil {
+					d.errorContext = new(errorContext)
+				}
 				d.errorContext.FieldStack = append(d.errorContext.FieldStack, f.name)
 				d.errorContext.Struct = t
 			} else if d.disallowUnknownFields {
@@ -812,11 +821,13 @@ func (d *decodeState) object(v reflect.Value) error {
 		if d.opcode == scanSkipSpace {
 			d.scanWhile(scanSkipSpace)
 		}
-		// Reset errorContext to its original state.
-		// Keep the same underlying array for FieldStack, to reuse the
-		// space and avoid unnecessary allocs.
-		d.errorContext.FieldStack = d.errorContext.FieldStack[:len(origErrorContext.FieldStack)]
-		d.errorContext.Struct = origErrorContext.Struct
+		if d.errorContext != nil {
+			// Reset errorContext to its original state.
+			// Keep the same underlying array for FieldStack, to reuse the
+			// space and avoid unnecessary allocs.
+			d.errorContext.FieldStack = d.errorContext.FieldStack[:len(origErrorContext.FieldStack)]
+			d.errorContext.Struct = origErrorContext.Struct
+		}
 		if d.opcode == scanEndObject {
 			break
 		}
diff --git a/libgo/go/encoding/json/encode.go b/libgo/go/encoding/json/encode.go
index 483b9d8..e473e61 100644
--- a/libgo/go/encoding/json/encode.go
+++ b/libgo/go/encoding/json/encode.go
@@ -794,23 +794,24 @@ func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 	e.WriteByte('{')
 
 	// Extract and sort the keys.
-	keys := v.MapKeys()
-	sv := make([]reflectWithString, len(keys))
-	for i, v := range keys {
-		sv[i].v = v
+	sv := make([]reflectWithString, v.Len())
+	mi := v.MapRange()
+	for i := 0; mi.Next(); i++ {
+		sv[i].k = mi.Key()
+		sv[i].v = mi.Value()
 		if err := sv[i].resolve(); err != nil {
 			e.error(fmt.Errorf("json: encoding error for type %q: %q", v.Type().String(), err.Error()))
 		}
 	}
-	sort.Slice(sv, func(i, j int) bool { return sv[i].s < sv[j].s })
+	sort.Slice(sv, func(i, j int) bool { return sv[i].ks < sv[j].ks })
 
 	for i, kv := range sv {
 		if i > 0 {
 			e.WriteByte(',')
 		}
-		e.string(kv.s, opts.escapeHTML)
+		e.string(kv.ks, opts.escapeHTML)
 		e.WriteByte(':')
-		me.elemEnc(e, v.MapIndex(kv.v), opts)
+		me.elemEnc(e, kv.v, opts)
 	}
 	e.WriteByte('}')
 	e.ptrLevel--
@@ -997,29 +998,30 @@ func typeByIndex(t reflect.Type, index []int) reflect.Type {
 }
 
 type reflectWithString struct {
-	v reflect.Value
-	s string
+	k  reflect.Value
+	v  reflect.Value
+	ks string
 }
 
 func (w *reflectWithString) resolve() error {
-	if w.v.Kind() == reflect.String {
-		w.s = w.v.String()
+	if w.k.Kind() == reflect.String {
+		w.ks = w.k.String()
 		return nil
 	}
-	if tm, ok := w.v.Interface().(encoding.TextMarshaler); ok {
-		if w.v.Kind() == reflect.Ptr && w.v.IsNil() {
+	if tm, ok := w.k.Interface().(encoding.TextMarshaler); ok {
+		if w.k.Kind() == reflect.Ptr && w.k.IsNil() {
 			return nil
 		}
 		buf, err := tm.MarshalText()
-		w.s = string(buf)
+		w.ks = string(buf)
 		return err
 	}
-	switch w.v.Kind() {
+	switch w.k.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		w.s = strconv.FormatInt(w.v.Int(), 10)
+		w.ks = strconv.FormatInt(w.k.Int(), 10)
 		return nil
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		w.s = strconv.FormatUint(w.v.Uint(), 10)
+		w.ks = strconv.FormatUint(w.k.Uint(), 10)
 		return nil
 	}
 	panic("unexpected map key type")
@@ -1239,19 +1241,18 @@ func typeFields(t reflect.Type) structFields {
 			// Scan f.typ for fields to include.
 			for i := 0; i < f.typ.NumField(); i++ {
 				sf := f.typ.Field(i)
-				isUnexported := sf.PkgPath != ""
 				if sf.Anonymous {
 					t := sf.Type
 					if t.Kind() == reflect.Ptr {
 						t = t.Elem()
 					}
-					if isUnexported && t.Kind() != reflect.Struct {
+					if !sf.IsExported() && t.Kind() != reflect.Struct {
 						// Ignore embedded fields of unexported non-struct types.
 						continue
 					}
 					// Do not ignore embedded fields of unexported struct types
 					// since they may have exported fields.
-				} else if isUnexported {
+				} else if !sf.IsExported() {
 					// Ignore unexported non-embedded fields.
 					continue
 				}
diff --git a/libgo/go/encoding/json/encode_test.go b/libgo/go/encoding/json/encode_test.go
index 42bb09d..0dad951 100644
--- a/libgo/go/encoding/json/encode_test.go
+++ b/libgo/go/encoding/json/encode_test.go
@@ -245,6 +245,22 @@ func TestUnsupportedValues(t *testing.T) {
 	}
 }
 
+// Issue 43207
+func TestMarshalTextFloatMap(t *testing.T) {
+	m := map[textfloat]string{
+		textfloat(math.NaN()): "1",
+		textfloat(math.NaN()): "1",
+	}
+	got, err := Marshal(m)
+	if err != nil {
+		t.Errorf("Marshal() error: %v", err)
+	}
+	want := `{"TF:NaN":"1","TF:NaN":"1"}`
+	if string(got) != want {
+		t.Errorf("Marshal() = %s, want %s", got, want)
+	}
+}
+
 // Ref has Marshaler and Unmarshaler methods with pointer receiver.
 type Ref int
 
@@ -854,6 +870,10 @@ func tenc(format string, a ...interface{}) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
+type textfloat float64
+
+func (f textfloat) MarshalText() ([]byte, error) { return tenc(`TF:%0.2f`, f) }
+
 // Issue 13783
 func TestEncodeBytekind(t *testing.T) {
 	testdata := []struct {
@@ -872,6 +892,7 @@ func TestEncodeBytekind(t *testing.T) {
 		{[]jsonint{5, 4}, `[{"JI":5},{"JI":4}]`},
 		{[]textint{9, 3}, `["TI:9","TI:3"]`},
 		{[]int{9, 3}, `[9,3]`},
+		{[]textfloat{12, 3}, `["TF:12.00","TF:3.00"]`},
 	}
 	for _, d := range testdata {
 		js, err := Marshal(d.data)
diff --git a/libgo/go/encoding/json/fuzz.go b/libgo/go/encoding/json/fuzz.go
index be03f0d..d3fa2d11 100644
--- a/libgo/go/encoding/json/fuzz.go
+++ b/libgo/go/encoding/json/fuzz.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build gofuzz
 // +build gofuzz
 
 package json
diff --git a/libgo/go/encoding/xml/typeinfo.go b/libgo/go/encoding/xml/typeinfo.go
index f30fe58..162724e 100644
--- a/libgo/go/encoding/xml/typeinfo.go
+++ b/libgo/go/encoding/xml/typeinfo.go
@@ -60,7 +60,7 @@ func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
 		n := typ.NumField()
 		for i := 0; i < n; i++ {
 			f := typ.Field(i)
-			if (f.PkgPath != "" && !f.Anonymous) || f.Tag.Get("xml") == "-" {
+			if (!f.IsExported() && !f.Anonymous) || f.Tag.Get("xml") == "-" {
 				continue // Private field
 			}
 
diff --git a/libgo/go/encoding/xml/xml.go b/libgo/go/encoding/xml/xml.go
index 6f9594d..c14954d 100644
--- a/libgo/go/encoding/xml/xml.go
+++ b/libgo/go/encoding/xml/xml.go
@@ -261,7 +261,7 @@ func NewTokenDecoder(t TokenReader) *Decoder {
 // call to Token. To acquire a copy of the bytes, call CopyToken
 // or the token's Copy method.
 //
-// Token expands self-closing elements such as <br/>
+// Token expands self-closing elements such as <br>
 // into separate start and end elements returned by successive calls.
 //
 // Token guarantees that the StartElement and EndElement
@@ -768,6 +768,12 @@ func (d *Decoder) rawToken() (Token, error) {
 					}
 					b0, b1 = b1, b
 				}
+
+				// Replace the comment with a space in the returned Directive
+				// body, so that markup parts that were separated by the comment
+				// (like a "<" and a "!") don't get joined when re-encoding the
+				// Directive, taking new semantic meaning.
+				d.buf.WriteByte(' ')
 			}
 		}
 		return Directive(d.buf.Bytes()), nil
@@ -1156,8 +1162,9 @@ func (d *Decoder) nsname() (name Name, ok bool) {
 	if !ok {
 		return
 	}
-	i := strings.Index(s, ":")
-	if i < 0 {
+	if strings.Count(s, ":") > 1 {
+		name.Local = s
+	} else if i := strings.Index(s, ":"); i < 1 || i > len(s)-2 {
 		name.Local = s
 	} else {
 		name.Space = s[0:i]
diff --git a/libgo/go/encoding/xml/xml_test.go b/libgo/go/encoding/xml/xml_test.go
index 5672ebb..19152db 100644
--- a/libgo/go/encoding/xml/xml_test.go
+++ b/libgo/go/encoding/xml/xml_test.go
@@ -802,11 +802,11 @@ var directivesWithCommentsInput = `
 
 var directivesWithCommentsTokens = []Token{
 	CharData("\n"),
-	Directive(`DOCTYPE [<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
+	Directive(`DOCTYPE [ <!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#">]`),
 	CharData("\n"),
-	Directive(`DOCTYPE [<!ENTITY go "Golang">]`),
+	Directive(`DOCTYPE [<!ENTITY go "Golang"> ]`),
 	CharData("\n"),
-	Directive(`DOCTYPE <!-> <!>    [<!ENTITY go "Golang">]`),
+	Directive(`DOCTYPE <!-> <!>       [<!ENTITY go "Golang"> ]`),
 	CharData("\n"),
 }
 
@@ -940,7 +940,7 @@ func (m mapper) Token() (Token, error) {
 }
 
 func TestNewTokenDecoderIdempotent(t *testing.T) {
-	d := NewDecoder(strings.NewReader(`<br/>`))
+	d := NewDecoder(strings.NewReader(`<br>`))
 	d2 := NewTokenDecoder(d)
 	if d != d2 {
 		t.Error("NewTokenDecoder did not detect underlying Decoder")
@@ -1003,3 +1003,60 @@ func TestTokenUnmarshaler(t *testing.T) {
 	d := NewTokenDecoder(tokReader{})
 	d.Decode(&Failure{})
 }
+
+func testRoundTrip(t *testing.T, input string) {
+	d := NewDecoder(strings.NewReader(input))
+	var tokens []Token
+	var buf bytes.Buffer
+	e := NewEncoder(&buf)
+	for {
+		tok, err := d.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("invalid input: %v", err)
+		}
+		if err := e.EncodeToken(tok); err != nil {
+			t.Fatalf("failed to re-encode input: %v", err)
+		}
+		tokens = append(tokens, CopyToken(tok))
+	}
+	if err := e.Flush(); err != nil {
+		t.Fatal(err)
+	}
+
+	d = NewDecoder(&buf)
+	for {
+		tok, err := d.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("failed to decode output: %v", err)
+		}
+		if len(tokens) == 0 {
+			t.Fatalf("unexpected token: %#v", tok)
+		}
+		a, b := tokens[0], tok
+		if !reflect.DeepEqual(a, b) {
+			t.Fatalf("token mismatch: %#v vs %#v", a, b)
+		}
+		tokens = tokens[1:]
+	}
+	if len(tokens) > 0 {
+		t.Fatalf("lost tokens: %#v", tokens)
+	}
+}
+
+func TestRoundTrip(t *testing.T) {
+	tests := map[string]string{
+		"leading colon":          `<::Test ::foo="bar"><:::Hello></:::Hello><Hello></Hello></::Test>`,
+		"trailing colon":         `<foo abc:="x"></foo>`,
+		"double colon":           `<x:y:foo></x:y:foo>`,
+		"comments in directives": `<!ENTITY x<!<!-- c1 [ " -->--x --> > <e></e> <!DOCTYPE xxx [ x<!-- c2 " -->--x ]>`,
+	}
+	for name, input := range tests {
+		t.Run(name, func(t *testing.T) { testRoundTrip(t, input) })
+	}
+}