[dev.typeparams] go/types: disallow "free" type parameter as RHS of a type declaration
This is a port of CL 332411 to go/types. methodset_test.go is similarly
updated.
Change-Id: I332b1837a954acc9d3b7e0e2ad2bec3425f088f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/335109 Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Robert Findley <rfindley@google.com>