test: add test that caused a gofrontend crash

For #51291

Change-Id: If47e4cbf899853ade5050852c3870b9500da4c63
Reviewed-on: https://go-review.googlesource.com/c/go/+/406916
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

Author: ianlancetaylor

test/fixedbugs/issue51291.dir/a.go

@@ -0,0 +1,9 @@
+// Copyright 2022 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.
+
+package a
+
+type TypeA string
+
+const StrA TypeA = "s"

test/fixedbugs/issue51291.dir/b.go

@@ -0,0 +1,11 @@
+// Copyright 2022 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.
+
+package b
+
+import "./a"
+
+type TypeB string
+
+const StrB TypeB = TypeB(a.StrA)

test/fixedbugs/issue51291.go

@@ -0,0 +1,9 @@
+// compiledir
+
+// Copyright 2022 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.
+
+package ignored
+
+// gofrontend crashed generating export data.