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Source file test/fixedbugs/issue13162.go

Documentation: test/fixedbugs

  // run
  
  // Copyright 2016 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.
  
  // Ensure that range loops over a string have the requisite side-effects.
  
  package main
  
  import (
  	"fmt"
  	"os"
  )
  
  func check(n int) {
  	var i int
  	var r rune
  
  	b := make([]byte, n)
  	for i = range b {
  		b[i] = byte(i + 1)
  	}
  	s := string(b)
  
  	// When n == 0, i is untouched by the range loop.
  	// Picking an initial value of -1 for i makes the
  	// "want" calculation below correct in all cases.
  	i = -1
  	for i = range s {
  		b[i] = s[i]
  	}
  	if want := n - 1; i != want {
  		fmt.Printf("index after range with side-effect = %d want %d\n", i, want)
  		os.Exit(1)
  	}
  
  	i = -1
  	r = '\x00'
  	for i, r = range s {
  		b[i] = byte(r)
  	}
  	if want := n - 1; i != want {
  		fmt.Printf("index after range with side-effect = %d want %d\n", i, want)
  		os.Exit(1)
  	}
  	if want := rune(n); r != want {
  		fmt.Printf("rune after range with side-effect = %q want %q\n", r, want)
  		os.Exit(1)
  	}
  
  	i = -1
  	// i is shadowed here, so its value should be unchanged.
  	for i := range s {
  		b[i] = s[i]
  	}
  	if want := -1; i != want {
  		fmt.Printf("index after range without side-effect = %d want %d\n", i, want)
  		os.Exit(1)
  	}
  
  	i = -1
  	r = -1
  	// i and r are shadowed here, so their values should be unchanged.
  	for i, r := range s {
  		b[i] = byte(r)
  	}
  	if want := -1; i != want {
  		fmt.Printf("index after range without side-effect = %d want %d\n", i, want)
  		os.Exit(1)
  	}
  	if want := rune(-1); r != want {
  		fmt.Printf("rune after range without side-effect = %q want %q\n", r, want)
  		os.Exit(1)
  	}
  }
  
  func main() {
  	check(0)
  	check(1)
  	check(15)
  }
  

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