This reverts commit 103b5b66.

Reason for revert: Breaks valid existing programs.

Updates #29458

Change-Id: I7ace4ae404cf2a8b0e15e646663c50115f74b758
Reviewed-on: https://go-review.googlesource.com/c/go/+/183939
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>