)

var IsSpace = isSpace

const DefaultBufSize = defaultBufSize

func (s *Scanner) MaxTokenSize(n int) {
	if n < utf8.UTFMax || n > 1e9 {
		panic("bad max token size")
	}
	if n < len(s.buf) {
		s.buf = make([]byte, n)
	}
	s.maxTokenSize = n
}

// ErrOrEOF is like Err, but returns EOF. Used to test a corner case.
func (s *Scanner) ErrOrEOF() error {
	return s.err

// Scan advances the [Scanner] to the next token, which will then be
// available through the [Scanner.Bytes] or [Scanner.Text] method. It returns false when
// there are no more tokens, either by reaching the end of the input or an error.
// After Scan returns false, the [Scanner.Err] method will return any error that
// occurred during scanning, except that if it was [io.EOF], [Scanner.Err]
// will return nil.

		w.Write(b)
	}
	w.Flush()
	// Output: 1 2 3 4
}

// The simplest use of a Scanner, to read standard input as a set of lines.
func ExampleScanner_lines() {
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		fmt.Println(scanner.Text()) // Println will add back the final '\n'
	}
	if err := scanner.Err(); err != nil {
		fmt.Fprintln(os.Stderr, "reading standard input:", err)
	}
}

	var s scanner.Scanner
	s.Init(r)
	// Newline is like a semicolon; other space characters are fine.
	s.Whitespace = 1<<'\t' | 1<<'\r' | 1<<' '
	// Don't skip comments: we need to count newlines.
	s.Mode = scanner.ScanChars |
		scanner.ScanFloats |
		scanner.ScanIdents |
		scanner.ScanInts |
		scanner.ScanStrings |
		scanner.ScanComments
	s.Position.Filename = name

	if err != nil {
		t.Fatalf("%v: %v\n%s", cmd, err, string(out))
	}
	syms := make(map[string]string)
	scanner := bufio.NewScanner(bytes.NewReader(out))
	for scanner.Scan() {
		f := strings.Fields(scanner.Text())
		if len(f) < 3 {
			continue
		}
		syms[f[2]] = f[0]
	}
	if err := scanner.Err(); err != nil {
		t.Fatalf("error reading symbols: %v", err)
	}
	return syms
}

package main

import (
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/scanner"
	"go/token"
	"os"
	"strings"
)

func parse(name string, src []byte, flags parser.Mode) *ast.File {
	ast1, err := parser.ParseFile(fset, name, src, flags)
	if err != nil {
		if list, ok := err.(scanner.ErrorList); ok {
			// If err is a scanner.ErrorList, its String will print just
			// the first error and then (+n more errors).

			t.Errorf("%d: %q evaluated to %d; expected %d", i, test.input, result, test.output)
		}
		tok := p.next()
		if test.atEOF && tok.ScanToken != scanner.EOF {
			t.Errorf("%d: %q: at EOF got %s", i, test.input, tok)
		} 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

			}
			in.beginningOfLine = in.hash()
			in.text = "#"
			return '#'

		case scanner.Ident:
			// Is it a macro name?
			name := in.Stack.Text()
			macro := in.macros[name]
			if macro != nil {
				nesting++
				in.invokeMacro(macro)
				continue
			}
			fallthrough
		default:
			if tok == scanner.EOF && len(in.ifdefStack) > 0 {
				// We're skipping text but have run out of input with no #endif.

		return
	}

	// Constant.
	haveConstant := false
	switch tok.ScanToken {
	case scanner.Int, scanner.Float, scanner.String, scanner.Char, '+', '-', '~':
		haveConstant = true
	case '(':
		// Could be parenthesized expression or (R). Must be something, though.
		tok := p.next()
		if tok.ScanToken == scanner.EOF {
			p.errorf("missing right parenthesis")
			return
		}
		rname := tok.String()
		p.back()

	switch t {
	case scanner.EOF:
		return "EOF"
	case scanner.Ident:
		return "identifier"
	case scanner.Int:
		return "integer constant"
	case scanner.Float:
		return "float constant"
	case scanner.Char:
		return "rune constant"
	case scanner.String:
		return "string constant"
	case scanner.RawString:
		return "raw string constant"
	case scanner.Comment:
		return "comment"
	default: