go/types: add test case for CL 486398

Forgot to 'git add' this test case in the CL.

Change-Id: Idde1d3d4525a99bdab0d3d69ac635a96a7cd5d73
Reviewed-on: https://go-review.googlesource.com/c/go/+/487335
Auto-Submit: Russ Cox <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: rsc

src/internal/types/testdata/check/go1_xx_19.go

@@ -0,0 +1,15 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+//go:build go1.19
+
+package p
+
+type Slice []byte
+type Array [8]byte
+
+var s Slice
+var p = (Array)(s /* ok because Go 1.X prior to Go 1.21 ignored the //go:build go1.19 */)