1// run
2
3// Copyright 2018 The Go Authors. All rights reserved.
4// Use of this source code is governed by a BSD-style
5// license that can be found in the LICENSE file.
6
7// Test order of evaluation of index operations.
8
9package main
10
11func main() {
12	arr := []int{1, 2}
13
14	// The spec says that in an assignment statement the operands
15	// of all index expressions and pointer indirections on the
16	// left, and the expressions on the right, are evaluated in
17	// the usual order. The usual order means function calls and
18	// channel operations are done first. Then the assignments are
19	// carried out one at a time. The operands of an index
20	// expression include both the array and the index. So this
21	// evaluates as
22	//   tmp1 := arr
23	//   tmp2 := len(arr) - 1
24	//   tmp3 := len(arr)
25	//   arr = arr[:tmp3-1]
26	//   tmp1[tmp2] = 3
27	arr, arr[len(arr)-1] = arr[:len(arr)-1], 3
28
29	if len(arr) != 1 || arr[0] != 1 || arr[:2][1] != 3 {
30		panic(arr)
31	}
32}
33