New test case, inspired by gccgo issue 30862.

Updates #30862.

Change-Id: I5e494b877e4fd142b8facb527471fe1fdef39c61
Reviewed-on: https://go-review.googlesource.com/c/go/+/167744
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>