func (t *Type) Common() *Type {
	return t
}

type ChanDir int

const (
	RecvDir    ChanDir = 1 << iota         // <-chan
	SendDir                                // chan<-
	BothDir            = RecvDir | SendDir // chan
	InvalidDir ChanDir = 0
)

// ChanType represents a channel type
type ChanType struct {
	Type
	Elem *Type
	Dir  ChanDir
}

type structTypeUncommon struct {
	StructType

		// x is a bidirectional channel value, T is a channel type,
		// and x's type V and T have identical element types.
		if V.ChanDir() == abi.BothDir && haveIdenticalType(T.Elem(), V.Elem(), cmpTags) {
			return true
		}

		// Otherwise continue test for identical underlying type.
		return V.ChanDir() == T.ChanDir() && haveIdenticalType(T.Elem(), V.Elem(), cmpTags)

	case abi.Func:
		t := (*funcType)(unsafe.Pointer(T))

		value := TypeExpr(f, pkg, t.Elem())
		if key == nil || value == nil {
			return nil
		}
		return &ast.MapType{
			Key:   key,
			Value: value,
		}
	case *types.Chan:
		dir := ast.ChanDir(t.Dir())
		if t.Dir() == types.SendRecv {
			dir = ast.SEND | ast.RECV
		}
		value := TypeExpr(f, pkg, t.Elem())
		if value == nil {
			return nil
		}
		return &ast.ChanType{
			Dir:   dir,

		return types.NewPointer(r.typ())
	case sliceType:
		return types.NewSlice(r.typ())
	case arrayType:
		n := r.uint64()
		return types.NewArray(r.typ(), int64(n))
	case chanType:
		dir := chanDir(int(r.uint64()))
		return types.NewChan(dir, r.typ())
	case mapType:
		return types.NewMap(r.typ(), r.typ())
	case signatureType:
		r.currPkg = r.pkg()
		return r.signature(nil, nil, nil)

	case pkgbits.TypeTypeParam:
		return r.dict.tparams[r.Len()]

	case pkgbits.TypeArray:
		len := int64(r.Uint64())
		return types.NewArray(r.typ(), len)
	case pkgbits.TypeChan:
		dir := types.ChanDir(r.Len())
		return types.NewChan(dir, r.typ())
	case pkgbits.TypeMap:
		return types.NewMap(r.typ(), r.typ())
	case pkgbits.TypePointer:
		return types.NewPointer(r.typ())
	case pkgbits.TypeSignature:

			break
		}
		om := fmtsort.Sort(val)
		for _, m := range om {
			oneIteration(m.Key, m.Value)
		}
		return
	case reflect.Chan:
		if val.IsNil() {
			break
		}
		if val.Type().ChanDir() == reflect.SendDir {
			s.errorf("range over send-only channel %v", val)
			break
		}
		i := 0
		for ; ; i++ {
			elem, ok := val.Recv()
			if !ok {
				break
			}