do not create interfaces containing interfaces

R=r
DELTA=16  (14 added, 0 deleted, 2 changed)
OCL=27464
CL=27466

src/lib/reflect/all_test.go

@@ -310,6 +310,12 @@ func TestInterfaceValue(t *testing.T) {
 	assert(v2.Type().String(), "interface { }");
 	v3 := v2.(reflect.InterfaceValue).Value();
 	assert(v3.Type().String(), "float");
+	
+	i3 := v2.Interface();
+	if f, ok := i3.(float); !ok {
+		a, typ, c := sys.Reflect(i3);
+		t.Error("v2.Interface() did not return float, got ", typ);
+	}
 }
 
 func TestFunctionValue(t *testing.T) {

src/lib/reflect/value.go

@@ -58,9 +58,12 @@ func (c *commonValue) Addr() Addr {
 
 func (c *commonValue) Interface() interface {} {
 	var i interface {};
-	if c.typ.Size() > 8 {	// TODO(rsc): how do we know it is 8?
+	switch {
+	case c.typ.Kind() == InterfaceKind:
+		i = *(*interface{})(c.addr);
+	case c.typ.Size() > 8:	// TODO(rsc): how do we know it is 8?
 		i = sys.Unreflect(uint64(uintptr(c.addr)), c.typ.String(), true);
-	} else {
+	default:
 		if uintptr(c.addr) == 0 {
 			panicln("reflect: address 0 for", c.typ.String());
 		}

src/runtime/iface.c

@@ -766,6 +766,11 @@ sys·Unreflect(uint64 it, String type, bool indir, Iface ret)
 	if(cmpstring(type, emptystring) == 0)
 		goto out;
 
+	if(type.len > 10 && mcmp(type.str, (byte*)"interface ", 10) == 0) {
+		printf("sys.Unreflect: cannot put %S in interface\n", type);
+		throw("sys.Unreflect");
+	}
+
 	// if we think the type should be indirect
 	// and caller does not, play it safe, return nil.
 	sigt = findtype(type, indir);