cmd/compile/internal/types2: better position for invalid slice indices error
Report the error at the first place (which is to say, latest index)
causing the error.
Change-Id: I31cf0a4d243fc66cfab84b7fec98055f4eb60ddf
Reviewed-on: https://go-review.googlesource.com/c/go/+/363671
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>