reflect: rename, document TestUnaddressableField

Change-Id: I94e0f3e4bccd44a67934ddb4d5fc7da57bb8ac9f
Reviewed-on: https://go-review.googlesource.com/33112Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

src/reflect/all_test.go

@@ -5914,8 +5914,13 @@ func TestSwapper(t *testing.T) {
 	}
 }
 
-func TestInaccessibleField(t *testing.T) {
-	var b Buffer
+// TestUnaddressableField tests that the reflect package will not allow
+// a type from another package to be used as a named type with an
+// unexported field.
+//
+// This ensures that unexported fields cannot be modified by other packages.
+func TestUnaddressableField(t *testing.T) {
+	var b Buffer // type defined in reflect, a different package
 	var localBuffer struct {
 		buf []byte
 	}