This only changes the type checkers and tests. Backend compiler changes are not included. For #77273. Change-Id: I8cf0b6fddf6afd6b08b06ba6fdf9c726af4bea8d Reviewed-on: https://go-review.googlesource.com/c/go/+/746820 Reviewed-by: Robert Griesemer <gri@google.com> Reviewed-by: Mark Freeman <markfreeman@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Auto-Submit: Robert Griesemer <gri@google.com>