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,
			Value: value,
		}
	case *types.Signature:
		var params []*ast.Field
		for i := 0; i < t.Params().Len(); i++ {
			p := TypeExpr(f, pkg, t.Params().At(i).Type())
			if p == nil {

			t.Incomplete = true
		}
		return len(t.Methods.List) > 0
	case *MapType:
		b1 := filterType(t.Key, f, export)
		b2 := filterType(t.Value, f, export)
		return b1 || b2
	case *ChanType:
		return filterType(t.Value, f, export)
	}
	return false
}

func filterSpec(spec Spec, f Filter, export bool) bool {
	switch s := spec.(type) {
	case *ValueSpec:

	BothDir = RecvDir | SendDir             // chan
)

// arrayType represents a fixed array type.
type arrayType = abi.ArrayType

// chanType represents a channel type.
type chanType = abi.ChanType

// funcType represents a function type.
//
// A *rtype for each in and out parameter is stored in an array that
// directly follows the funcType (and possibly its uncommonType). So

	t := new(types.Map)
	p.update(t, nlist)

	p.expect('[')
	key := p.parseType(pkg)
	p.expect(']')
	elem := p.parseType(pkg)

	*t = *types.NewMap(key, elem)
	return t
}

// ChanType = "chan" ["<-" | "-<"] Type .
func (p *parser) parseChanType(pkg *types.Package, nlist []any) types.Type {
	p.expectKeyword("chan")

	t := new(types.Chan)
	p.update(t, nlist)

	dir := types.SendRecv

	case *ast.InterfaceType:
		a.apply(n, "Methods", nil, n.Methods)

	case *ast.MapType:
		a.apply(n, "Key", nil, n.Key)
		a.apply(n, "Value", nil, n.Value)

	case *ast.ChanType:
		a.apply(n, "Value", nil, n.Value)

	// Statements
	case *ast.BadStmt:
		// nothing to do

	case *ast.DeclStmt:
		a.apply(n, "Decl", nil, n.Decl)

	case *ast.EmptyStmt:
		// nothing to do

}

// Chan contains Type fields specific to channel types.
type Chan struct {
	Elem *Type   // element type
	Dir  ChanDir // channel direction
}

// chanType returns t's extra channel-specific fields.
func (t *Type) chanType() *Chan {
	t.wantEtype(TCHAN)
	return t.extra.(*Chan)
}

type Tuple struct {
	first  *Type
	second *Type

		off += arch.PtrSize // 4 bytes, pointer aligned
	case abi.Slice: // reflect.sliceType
		off += arch.PtrSize
	case abi.Array: // reflect.arrayType
		off += 3 * arch.PtrSize
	case abi.Chan: // reflect.chanType
		off += 2 * arch.PtrSize
	case abi.Map: // reflect.mapType
		off += 4*arch.PtrSize + 8
	case abi.Interface: // reflect.interfaceType
		off += 3 * arch.PtrSize
	default:
		// just Sizeof(rtype)
	}

				}
				check.errorf(e.Key, IncomparableMapKey, "invalid map key type %s%s", typ.key, why)
			}
		}).describef(e.Key, "check map key %s", typ.key)

		return typ

	case *ast.ChanType:
		typ := new(Chan)
		setDefType(def, typ)

		dir := SendRecv
		switch e.Dir {
		case ast.SEND | ast.RECV:
			// nothing to do
		case ast.SEND:
			dir = SendOnly
		case ast.RECV:

				}
				check.errorf(e.Key, IncomparableMapKey, "invalid map key type %s%s", typ.key, why)
			}
		}).describef(e.Key, "check map key %s", typ.key)

		return typ

	case *syntax.ChanType:
		typ := new(Chan)
		setDefType(def, typ)

		dir := SendRecv
		switch e.Dir {
		case 0:
			// nothing to do
		case syntax.SendOnly:
			dir = SendOnly
		case syntax.RecvOnly:

func isTypeElem(x ast.Expr) bool {
	switch x := x.(type) {
	case *ast.ArrayType, *ast.StructType, *ast.FuncType, *ast.InterfaceType, *ast.MapType, *ast.ChanType:
		return true
	case *ast.UnaryExpr:
		return x.Op == token.TILDE
	case *ast.BinaryExpr:
		return isTypeElem(x.X) || isTypeElem(x.Y)
	case *ast.ParenExpr:
		return isTypeElem(x.X)
	}
	return false