go/types, types2: verify stateMask transitions in debug mode
Recently, we've changed the representation of Named type state from
an integer to a bit mask, which is a bit more complicated. To make
sure we uphold state invariants, we are adding a verification step
on each state transition.
This uncovered a few places where we do not uphold the transition
invariants; those are patched in this CL.
Change-Id: I76569e4326b2d362d7a1f078641029ffb3dca531
Reviewed-on: https://go-review.googlesource.com/c/go/+/714241
Auto-Submit: Mark Freeman <markfreeman@google.com> Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>