[dev.typeparams] cmd/compile/internal/types: minor fixes/cleanups aro…

…und testing

Also, implemented isConstType predicate in terms of "is" predicate.

Change-Id: Ib3b311f52196dba974802348bc6d63307530d915
Reviewed-on: https://go-review.googlesource.com/c/go/+/284217
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>

src/cmd/compile/internal/types2/check_test.go

@@ -47,12 +47,12 @@ var (
 	testFiles   = flag.String("files", "", "space-separated list of test files")
 )
 
-func parseFiles(t *testing.T, filenames []string) ([]*syntax.File, []error) {
+func parseFiles(t *testing.T, filenames []string, mode syntax.Mode) ([]*syntax.File, []error) {
 	var files []*syntax.File
 	var errlist []error
 	errh := func(err error) { errlist = append(errlist, err) }
 	for _, filename := range filenames {
-		file, err := syntax.ParseFile(filename, errh, nil, syntax.AllowGenerics)
+		file, err := syntax.ParseFile(filename, errh, nil, mode)
 		if file == nil {
 			t.Fatalf("%s: %s", filename, err)
 		}
@@ -84,8 +84,16 @@ func delta(x, y uint) uint {
 }
 
 func checkFiles(t *testing.T, sources []string, colDelta uint, trace bool) {
+	if len(sources) == 0 {
+		t.Fatal("no source files")
+	}
+
+	var mode syntax.Mode
+	if strings.HasSuffix(sources[0], ".go2") {
+		mode |= syntax.AllowGenerics
+	}
 	// parse files and collect parser errors
-	files, errlist := parseFiles(t, sources)
+	files, errlist := parseFiles(t, sources, mode)
 
 	pkgName := "<no package>"
 	if len(files) > 0 {

src/cmd/compile/internal/types2/predicates.go

@@ -73,12 +73,8 @@ func isUntyped(typ Type) bool {
 	return !isTyped(typ)
 }
 
-func isOrdered(typ Type) bool { return is(typ, IsOrdered) }
-
-func isConstType(typ Type) bool {
-	t := typ.Basic()
-	return t != nil && t.info&IsConstType != 0
-}
+func isOrdered(typ Type) bool   { return is(typ, IsOrdered) }
+func isConstType(typ Type) bool { return is(typ, IsConstType) }
 
 // IsInterface reports whether typ is an interface type.
 func IsInterface(typ Type) bool {

src/cmd/compile/internal/types2/testdata/expr3.src

@@ -145,10 +145,6 @@ func indexes() {
 	ms = "foo" /* ERROR "cannot use .* in assignment" */ [1:2]
 	ms = "foo" /* ERROR "cannot use .* in assignment" */ [i:j]
 	_, _ = ss, ms
-
-	// With type parameters, index expressions may have multiple indices.
-	_ = a[i, j /* ERROR "more than one index" */ ]
-	_ = a[i, j /* ERROR "more than one index" */ , j]
 }
 
 type T struct {