go/types, types2: better error message for invalid method expression
Fixes #53358.
Change-Id: I38528da1596b6e1aaedcab89b1513fb8acac596c
Reviewed-on: https://go-review.googlesource.com/c/go/+/455335
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>