reflect: define MyBuffer more locally in TestImplicitMapConversion

There are no strange messages anymore, so define type MyBuffer in the
block where it is used.

Change-Id: Ic65b15dc76a40f6f734d9ac2116338502fbb66fd
Reviewed-on: https://go-review.googlesource.com/107735
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/reflect/set_test.go

@@ -14,8 +14,6 @@ import (
 	"unsafe"
 )
 
-type MyBuffer bytes.Buffer
-
 func TestImplicitMapConversion(t *testing.T) {
 	// Test implicit conversions in MapIndex and SetMapIndex.
 	{
@@ -102,10 +100,7 @@ func TestImplicitMapConversion(t *testing.T) {
 	}
 	{
 		// convert identical underlying types
-		// TODO(rsc): Should be able to define MyBuffer here.
-		// 6l prints very strange messages about .this.Bytes etc
-		// when we do that though, so MyBuffer is defined
-		// at top level.
+		type MyBuffer bytes.Buffer
 		m := make(map[*MyBuffer]*bytes.Buffer)
 		mv := ValueOf(m)
 		b1 := new(MyBuffer)