go/types: implement NewTypeList and use it instead of composite literals

Also, simplify a bit of code in predicates.go.

This is a backport of changes in CL 344615 that were made in addition
to the changes of the original CL 343933; it brings go/types in sync
with types2.

Change-Id: I14cd4d4704d29894d0fbb8d129744d65e332ad22
Reviewed-on: https://go-review.googlesource.com/c/go/+/344570
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

1 files changed, 3 insertions, 5 deletions

diff --git a/src/go/types/predicates.go b/src/go/types/predicates.go
index 2f4ef9dace..d4055bb0cc 100644
--- a/src/go/types/predicates.go
+++ b/src/go/types/predicates.go
@@ -312,16 +312,14 @@ func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
 				return false
 			}
 
-			if nargs := len(xargs); nargs > 0 {
+			if len(xargs) > 0 {
 				// Instances are identical if their original type and type arguments
 				// are identical.
 				if !Identical(x.orig, y.orig) {
 					return false
 				}
-				for i := 0; i < nargs; i++ {
-					xa := xargs[i]
-					ya := yargs[i]
-					if !Identical(xa, ya) {
+				for i, xa := range xargs {
+					if !Identical(xa, yargs[i]) {
 						return false
 					}
 				}