Add a vet pass that checks that the second argument to errors.As
is a pointer to a type implementing error.
Change-Id: I0924e634cbea0664c8728f0e74213b924f8498e6
Reviewed-on: https://go-review.googlesource.com/c/tools/+/168938
Reviewed-by: Damien Neil <dneil@google.com>
Jonathan Amsterdam