test: add test case that gofrontend miscompiled

For #47771

Change-Id: I99dfdd48def756bde68445b50741afd6d86b6cf2
Reviewed-on: https://go-review.googlesource.com/c/go/+/344169
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/test/fixedbugs/issue47771.go b/test/fixedbugs/issue47771.go
new file mode 100644
index 0000000000..a434bffe4b
--- /dev/null
+++ b/test/fixedbugs/issue47771.go
@@ -0,0 +1,19 @@
+// run
+
+// Copyright 2021 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.
+
+// gofrontend miscompiled some cases of append(s, make(typ, ln)...).
+
+package main
+
+var g int
+
+func main() {
+	a := []*int{&g, &g, &g, &g}
+	a = append(a[:0], make([]*int, len(a) - 1)...)
+	if len(a) != 3 || a[0] != nil || a[1] != nil || a[2] != nil {
+		panic(a)
+	}
+}