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-rw-r--r--test/fixedbugs/issue23188.go32
1 files changed, 32 insertions, 0 deletions
diff --git a/test/fixedbugs/issue23188.go b/test/fixedbugs/issue23188.go
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@@ -0,0 +1,32 @@
+// run
+
+// Copyright 2018 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.
+
+// Test order of evaluation of index operations.
+
+package main
+
+func main() {
+ arr := []int{1, 2}
+
+ // The spec says that in an assignment statement the operands
+ // of all index expressions and pointer indirections on the
+ // left, and the expressions on the right, are evaluated in
+ // the usual order. The usual order means function calls and
+ // channel operations are done first. Then the assignments are
+ // carried out one at a time. The operands of an index
+ // expression include both the array and the index. So this
+ // evaluates as
+ // tmp1 := arr
+ // tmp2 := len(arr) - 1
+ // tmp3 := len(arr)
+ // arr = arr[:tmp3-1]
+ // tmp1[tmp2] = 3
+ arr, arr[len(arr)-1] = arr[:len(arr)-1], 3
+
+ if len(arr) != 1 || arr[0] != 1 || arr[:2][1] != 3 {
+ panic(arr)
+ }
+}