Handle the case where there is syntactically only one actual argument
passed to errors.As.
Following the unmarshal check, we ignore this case.
Change-Id: Ia7d77d5b3c9eb5416b37a141104c9ad7ed290b5f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/178159
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>