buf.WriteString("map[")
		w.writeType(buf, typ.Key())
		buf.WriteByte(']')
		w.writeType(buf, typ.Elem())

	case *types.Chan:
		var s string
		switch typ.Dir() {
		case types.SendOnly:
			s = "chan<- "
		case types.RecvOnly:
			s = "<-chan "
		case types.SendRecv:
			s = "chan "
		default:
			panic("unreachable")
		}
		buf.WriteString(s)
		w.writeType(buf, typ.Elem())

	case *types.Alias: