[release-branch.go1.22] go/types, types2: ensure that Alias.actual is set in NewAlias
Types returned by the go/types API must be immutable (or at least
concurrency safe), but NewAlias returned an alias without actual set.
Ensure that actual is set by unaliasing. Also make some superficial
simplifications to unalias, and avoid indirection where unnecessary.
Fixes golang/go#65728
Change-Id: Ic9a020da5accf9032056a924b65c9e9e08cb2e0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/560915
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Robert Griesemer <gri@google.com>
(cherry picked from commit
10a65649a3b2e34ffe8e4202bfa3df851cea0fb4)
Reviewed-on: https://go-review.googlesource.com/c/go/+/564356