}

	// A MapType node represents a map type.
	MapType struct {
		Map   token.Pos // position of "map" keyword
		Key   Expr
		Value Expr
	}

	// A ChanType node represents a channel type.
	ChanType struct {
		Begin token.Pos // position of "chan" keyword or "<-" (whichever comes first)
		Arrow token.Pos // position of "<-" (token.NoPos if there is no "<-")
		Dir   ChanDir   // channel direction

			children = append(children,
				tok(n.Case, len("default")))
		} else {
			children = append(children,
				tok(n.Case, len("case")))
		}
		children = append(children, tok(n.Colon, len(":")))

	case *ast.ChanType:
		switch n.Dir {
		case ast.RECV:
			children = append(children, tok(n.Begin, len("<-chan")))
		case ast.SEND:
			children = append(children, tok(n.Begin, len("chan<-")))
		case ast.RECV | ast.SEND:

			Walk(v, n.Params)
		}
		if n.Results != nil {
			Walk(v, n.Results)
		}

	case *InterfaceType:
		Walk(v, n.Methods)

	case *MapType:
		Walk(v, n.Key)
		Walk(v, n.Value)

	case *ChanType:
		Walk(v, n.Value)

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

	case *DeclStmt:
		Walk(v, n.Decl)

	case *EmptyStmt:
		// nothing to do

	case *LabeledStmt:

	case *ast.ArrayType:
		if t.Len == nil {
			return fmt.Sprintf("types.NewSlice(%s)", i.subtype(t.Elt))
		}
		return fmt.Sprintf("types.NewArray(%s, %d)", i.subtype(t.Elt), intconst(t.Len))
	case *ast.ChanType:
		dir := "types.Cboth"
		switch t.Dir {
		case ast.SEND:
			dir = "types.Csend"
		case ast.RECV:
			dir = "types.Crecv"
		}
		return fmt.Sprintf("types.NewChan(%s, %s)", i.subtype(t.Value), dir)

	case *InterfaceType:
		w.fieldList(n.MethodList)

	case *FuncType:
		w.fieldList(n.ParamList)
		w.fieldList(n.ResultList)

	case *MapType:
		w.node(n.Key)
		w.node(n.Value)

	case *ChanType:
		w.node(n.Elem)

	// statements
	case *EmptyStmt: // nothing to do

	case *LabeledStmt:
		w.node(n.Label)
		w.node(n.Stmt)

	case *BlockStmt:
		w.stmtList(n.List)

type ident struct {
	pkg  *types.Package
	name string
}

const predeclReserved = 32

type itag uint64

const (
	// Types
	definedType itag = iota
	pointerType
	sliceType
	arrayType
	chanType
	mapType
	signatureType
	structType
	interfaceType
	typeParamType
	instanceType
	unionType
)

// iImportData imports a package from the serialized package data

	case *ast.InterfaceType:
		if r.filterFieldList(parent, t.Methods, t) {
			t.Incomplete = true
		}
	case *ast.MapType:
		r.filterType(nil, t.Key)
		r.filterType(nil, t.Value)
	case *ast.ChanType:
		r.filterType(nil, t.Value)
	}
}

func (r *reader) filterSpec(spec ast.Spec) bool {
	switch s := spec.(type) {
	case *ast.ImportSpec:
		// always keep imports so we can collect them
		return true

		ParamList  []*Field
		ResultList []*Field
		expr
	}

	// map[Key]Value
	MapType struct {
		Key, Value Expr
		expr
	}

	//   chan Elem
	// <-chan Elem
	// chan<- Elem
	ChanType struct {
		Dir  ChanDir // 0 means no direction
		Elem Expr
		expr
	}
)

type expr struct {
	node
	typeAndValue // After typechecking, contains the results of typechecking this expression.
}

}

//go:linkname reflect_makechan reflect.makechan
func reflect_makechan(t *chantype, size int) *hchan {
	return makechan(t, size)
}

func makechan64(t *chantype, size int64) *hchan {
	if int64(int(size)) != size {
		panic(plainError("makechan: size out of range"))
	}

	return makechan(t, int(size))
}

func makechan(t *chantype, size int) *hchan {
	elem := t.Elem

	// compiler checks this but be safe.

	key := p.parseType()
	p.expect(token.RBRACK)
	value := p.parseType()

	return &ast.MapType{Map: pos, Key: key, Value: value}
}

func (p *parser) parseChanType() *ast.ChanType {
	if p.trace {
		defer un(trace(p, "ChanType"))
	}

	pos := p.pos
	dir := ast.SEND | ast.RECV
	var arrow token.Pos
	if p.tok == token.CHAN {
		p.next()
		if p.tok == token.ARROW {
			arrow = p.pos