[dev.typeparams] cmd/compile/internal/types2: more consistent handling of predeclared "any"
Rather than removing "any" from the universe scope, keep it predeclared
but provide a better error message.
While at it, remove some unnecessary type assertions.
Change-Id: I10603274282ea6afc107f703ab194f32bd334dd1
Reviewed-on: https://go-review.googlesource.com/c/go/+/334911
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>