go/internal/gcimporter: don't use Interface.EmbeddedType for builds before go1.11

For https://github.com/golang/lint/issues/402.

Change-Id: I3f4eab123e52460980e76f5ffaca3a77a3af7374
Reviewed-on: https://go-review.googlesource.com/118565
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

go/internal/gcimporter/gcimporter_test.go

@@ -336,7 +336,7 @@ func verifyInterfaceMethodRecvs(t *testing.T, named *types.Named, level int) {
 	// check embedded interfaces (if they are named, too)
 	for i := 0; i < iface.NumEmbeddeds(); i++ {
 		// embedding of interfaces cannot have cycles; recursion will terminate
-		if etype, _ := iface.EmbeddedType(i).(*types.Named); etype != nil {
+		if etype, _ := embeddedType(iface, i).(*types.Named); etype != nil {
 			verifyInterfaceMethodRecvs(t, etype, level+1)
 		}
 	}

go/internal/gcimporter/newInterface10.go

@@ -19,3 +19,7 @@ func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interfac
 	}
 	return types.NewInterface(methods, named)
 }
+
+func embeddedType(iface *types.Interface, i int) types.Type {
+	return iface.Embedded(i)
+}

go/internal/gcimporter/newInterface11.go

@@ -11,3 +11,7 @@ import "go/types"
 func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interface {
 	return types.NewInterface2(methods, embeddeds)
 }
+
+func embeddedType(iface *types.Interface, i int) types.Type {
+	return iface.EmbeddedType(i)
+}