Type aliases don't work well with types.TypeString. Work around that by
using the AST to build this information. Follow up from CL 201677.
Fixesgolang/go#33500
Change-Id: I8b2d4ea238eb5d284a419f2b0bbf9655e69d434d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/208497
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>