go/types, types2: reduce locks held at once in resolveUnderlying
There is no need to hold locks for the entire chain of Named types in
resolveUnderlying. This change moves the locking / unlocking right to
where t.underlying is set.
This change consolidates logic into resolveUnderlying where possible
and makes minor stylistic / documentation adjustments.
Change-Id: Ic5ec5a7e9a0da8bc34954bf456e4e23a28df296d
Reviewed-on: https://go-review.googlesource.com/c/go/+/714403 Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Mark Freeman <markfreeman@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>