// We have channels that differ in direction only.
			// If there's an unrestricted channel, select the restricted one.
			switch {
			case x.dir == SendRecv:
				return y
			case y.dir == SendRecv:
				return x
			}
		}
	}

	// types are different
	return nil

type Chan struct {
	dir  ChanDir
	elem Type
}

// A ChanDir value indicates a channel direction.
type ChanDir int

// The direction of a channel is indicated by one of these constants.
const (
	SendRecv ChanDir = iota
	SendOnly
	RecvOnly
)

// NewChan returns a new channel type for the given direction and element type.
func NewChan(dir ChanDir, elem Type) *Chan {
	return &Chan{dir: dir, elem: elem}
}

			// We have channels that differ in direction only.
			// If there's an unrestricted channel, select the restricted one.
			switch {
			case x.dir == SendRecv:
				return y
			case y.dir == SendRecv:
				return x
			}
		}
	}

	// types are different
	return nil

			return nil
		}
		if !types.Identical(ch.Elem(), curr.Elem()) {
			return nil // channel elements are not identical.
		}
		if ch.Dir() == types.SendRecv {
			// ch is bidirectional. We can safely always use curr's direction.
			ch = curr
		} else if curr.Dir() != types.SendRecv && ch.Dir() != curr.Dir() {
			// ch and curr are not bidirectional and not the same direction.
			return nil
		}
	}
	return ch
}

	// tag values must match the constants in cmd/compile/internal/gc/go.go
	switch d {
	case 1 /* Crecv */ :
		return types.RecvOnly
	case 2 /* Csend */ :
		return types.SendOnly
	case 3 /* Cboth */ :
		return types.SendRecv
	default:
		errorf("unexpected channel dir %d", d)
		return 0
	}
}

var predeclared = []types.Type{
	// basic types
	types.Typ[types.Bool],
	types.Typ[types.Int],
	types.Typ[types.Int8],

//         Tag  itag // arrayType
//         Len  uint64
//         Elem typeOff
//     }
//
//     type ChanType struct {
//         Tag  itag   // chanType
//         Dir  uint64 // 1 RecvOnly; 2 SendOnly; 3 SendRecv
//         Elem typeOff
//     }
//
//     type MapType struct {
//         Tag  itag // mapType
//         Key  typeOff
//         Elem typeOff
//     }
//
//     type FuncType struct {