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-rw-r--r--test/fixedbugs/issue21687.go68
1 files changed, 68 insertions, 0 deletions
diff --git a/test/fixedbugs/issue21687.go b/test/fixedbugs/issue21687.go
new file mode 100644
index 0000000..9b4c03f
--- /dev/null
+++ b/test/fixedbugs/issue21687.go
@@ -0,0 +1,68 @@
+// run
+
+// Copyright 2017 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.
+
+// Issue 21687: cmd/compile evaluates x twice in "x op= y", which was
+// detectable if evaluating y affects x.
+
+package main
+
+func ptrs() (int, int) {
+ one := 1
+ two := 2
+
+ x := &one
+ *x += func() int {
+ x = &two
+ return 0
+ }()
+
+ return one, two
+}
+
+func slices() (int, int) {
+ one := []int{1}
+ two := []int{2}
+
+ x := one
+ x[0] += func() int {
+ x = two
+ return 0
+ }()
+
+ return one[0], two[0]
+}
+
+func maps() (int, int) {
+ one := map[int]int{0: 1}
+ two := map[int]int{0: 2}
+
+ x := one
+ x[0] += func() int {
+ x = two
+ return 0
+ }()
+
+ return one[0], two[0]
+}
+
+var tests = [...]func() (int, int){
+ ptrs,
+ slices,
+ maps,
+}
+
+func main() {
+ bad := 0
+ for i, f := range tests {
+ if a, b := f(); a+b != 3 {
+ println(i, a, b)
+ bad++
+ }
+ }
+ if bad != 0 {
+ panic(bad)
+ }
+}