[dev.typeparams] cmd/compile/internal/types2: remove Type.Under method in favor of function

This removes the need for the aType embedded type and brings the types2.Type
API in sync with the go/types.Type API.

For reasons not fully understood yet, introducing the new under function
causes a very long initialization cycle error, which doesn't exist in
go/types. For now, circumvent the problem through a helper function variable.

This CL also eliminates superflous (former) Under() method calls
inside optype calls (optype takes care of this).

Plus some minor misc. cleanups and comment adjustments.

Change-Id: I86e13ccf6f0b34d7496240ace61a1c84856b6033
Reviewed-on: https://go-review.googlesource.com/c/go/+/293470
Reviewed-by: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/types2/unify.go b/src/cmd/compile/internal/types2/unify.go
index 153df9d622..d2ea2b952b 100644
--- a/src/cmd/compile/internal/types2/unify.go
+++ b/src/cmd/compile/internal/types2/unify.go
@@ -215,9 +215,9 @@ func (u *unifier) nify(x, y Type, p *ifacePair) bool {
 		// want *Named types.)
 		switch {
 		case !isNamed(x) && y != nil && asNamed(y) != nil:
-			return u.nify(x, y.Under(), p)
+			return u.nify(x, under(y), p)
 		case x != nil && asNamed(x) != nil && !isNamed(y):
-			return u.nify(x.Under(), y, p)
+			return u.nify(under(x), y, p)
 		}
 	}