cmd/compile: fixed which-result confusion in presence of 0-width types
A function returning multiple results, some of them zero-width,
will have more than one result present at an offset. Be sure
that offset AND type match.
Includes test.
Change-Id: I3eb1f56116d989b4e73f533fefabb1bf554c901b
Reviewed-on: https://go-review.googlesource.com/c/go/+/297169
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Jeremy Faller <jeremy@golang.org>