}

// Use a Scanner with a custom split function to parse a comma-separated
// list with an empty final value.
func ExampleScanner_emptyFinalToken() {
	// Comma-separated list; last entry is empty.
	const input = "1,2,3,4,"
	scanner := bufio.NewScanner(strings.NewReader(input))
	// Define a split function that separates on commas.

The [Map.Clear] method deletes all the entries, resulting in

Empty directory for test, see https://golang.org/issues/29837....

		} else if !test.atEOF && tok.ScanToken == scanner.EOF {
			t.Errorf("%d: %q: expected not EOF but at EOF", i, test.input)
		}
	}
}

type badExprTest struct {
	input string
	error string // Empty means no error.
}

var badExprTests = []badExprTest{
	{"0/0", "division by zero"},
	{"3/0", "division by zero"},
	{"(1<<63)/0", "divide of value with high bit set"},
	{"3%0", "modulo by zero"},

	if err != nil {
		return nil, err
	}
	return bytes.TrimSpace(out), nil
}

func getLines(cmd *exec.Cmd) [][]byte {
	out := output(cmd)
	lines := bytes.Split(out, []byte("\n"))
	// Skip the empty line at the end.
	if len(lines[len(lines)-1]) == 0 {
		lines = lines[:len(lines)-1]
	}
	return lines
}

func output(cmd *exec.Cmd) []byte {
	out, err := cmd.Output()
	if err != nil {

// io.ByteScanner, and io.RuneScanner interfaces by reading from
// a byte slice.
// Unlike a [Buffer], a Reader is read-only and supports seeking.
// The zero value for Reader operates like a Reader of an empty slice.
type Reader struct {
	s        []byte
	i        int64 // current reading index
	prevRune int   // index of previous rune; or < 0
}

// Len returns the number of bytes of the unread portion of the
// slice.

		// should not happen
		t.Fatal(err)
	}
	if err := buf.UnreadByte(); err == nil {
		t.Fatal("UnreadByte: expected error, got nil")
	}
}

// verify that copying from an empty reader always has the same results,
// regardless of the presence of a WriteTo method.
func TestReaderCopyNothing(t *testing.T) {
	type nErr struct {
		n   int64
		err error
	}
	type justReader struct {

package lex

import (
	"strings"
	"testing"
	"text/scanner"
)

type lexTest struct {
	name   string
	input  string
	output string
}

var lexTests = []lexTest{
	{
		"empty",
		"",
		"",
	},
	{
		"simple",
		"1 (a)",
		"1.(.a.)",
	},
	{
		"simple define",
		lines(
			"#define A 1234",
			"A",
		),
		"1234.\n",
	},
	{
		"define without value",