go/types: remove some unnecessary loading/expansion of Named types

For Identical an u.nify, only type arguments and pointer identity is
needed.

Change-Id: Id4018d2a53044fa20fd26d28890f28b37b6d6d70
Reviewed-on: https://go-review.googlesource.com/c/go/+/349409
Trust: Robert Findley <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>

Author: findleyr

src/go/types/predicates.go

@@ -302,9 +302,6 @@ func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
 		// Two named types are identical if their type names originate
 		// in the same type declaration.
 		if y, ok := y.(*Named); ok {
-			x.expand(nil)
-			y.expand(nil)
-
 			xargs := x.TypeArgs().list()
 			yargs := y.TypeArgs().list()
 

src/go/types/unify.go

@@ -425,9 +425,6 @@ func (u *unifier) nify(x, y Type, p *ifacePair) bool {
 
 	case *Named:
 		if y, ok := y.(*Named); ok {
-			x.expand(nil)
-			y.expand(nil)
-
 			xargs := x.targs.list()
 			yargs := y.targs.list()