See https://go.dev/s/generatedcode for spec.
Fixes#28089
Change-Id: Ic9bb138bdd180f136f9e8e74e187319acca5dbac
Reviewed-on: https://go-review.googlesource.com/c/go/+/487935
Run-TryBot: Alan Donovan <adonovan@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>