// Sets multiLine to true if the declaration spans multiple lines.
func (p *printer) genDecl(d *ast.GenDecl, multiLine *bool) {
	p.setComment(d.Doc)
	p.print(d.Pos(), d.Tok, blank)

	if d.Lparen.IsValid() {
		// group of parenthesized declarations
		p.print(d.Lparen, token.LPAREN)
		if len(d.Specs) > 0 {
			p.print(indent, formfeed)
			var ml bool
			for i, s := range d.Specs {
				if i > 0 {
					p.linebreak(s.Pos().Line, 1, ignore, ml)
				}
				ml = false
				p.spec(s, len(d.Specs), false, &ml)
			}
			p.print(unindent, formfeed)
			*multiLine = true
		}
		p.print(d.Rparen, token.RPAREN)

	} else {
		// single declaration
		p.spec(d.Specs[0], 1, true, multiLine)
	}
}

func constDecl(kind token.Token, args ...string) *ast.GenDecl {
	decl := ast.GenDecl{Tok: token.CONST}

	if len(args)%3 != 0 {
		panic("Number of values passed to ConstString must be a multiple of 3")
	}
	for i := 0; i < len(args); i += 3 {
		name, typ, val := args[i], args[i+1], args[i+2]
		lit := &ast.BasicLit{Kind: kind}
		if kind == token.STRING {
			lit.Value = strconv.Quote(val)
		} else {
			lit.Value = val
		}
		a := &ast.ValueSpec{
			Names:  []*ast.Ident{ast.NewIdent(name)},
			Values: []ast.Expr{lit},
		}
		if typ != "" {
			a.Type = ast.NewIdent(typ)
		}
		decl.Specs = append(decl.Specs, a)
	}

	if len(decl.Specs) > 1 {
		decl.Lparen = 1
	}

	return &decl
}

// addImport adds the import path to the file f, if absent.
func addImport(f *ast.File, path string) {
	if imports(f, path) {
		return
	}

	newImport := &ast.ImportSpec{
		Path: &ast.BasicLit{
			Kind:  token.STRING,
			Value: strconv.Quote(path),
		},
	}

	var impdecl *ast.GenDecl

	// Find an import decl to add to.
	for _, decl := range f.Decls {
		gen, ok := decl.(*ast.GenDecl)

		if ok && gen.Tok == token.IMPORT {
			impdecl = gen
			break
		}
	}

	// No import decl found.  Add one.
	if impdecl == nil {
		impdecl = &ast.GenDecl{
			Tok: token.IMPORT,
		}
		f.Decls = append(f.Decls, nil)
		copy(f.Decls[1:], f.Decls)
		f.Decls[0] = impdecl
	}

	// Ensure the import decl has parentheses, if needed.
	if len(impdecl.Specs) > 0 && !impdecl.Lparen.IsValid() {
		impdecl.Lparen = impdecl.Pos()
	}

	// Assume the import paths are alphabetically ordered.
	// If they are not, the result is ugly, but legal.
	insertAt := len(impdecl.Specs) // default to end of specs
	for i, spec := range impdecl.Specs {
		impspec := spec.(*ast.ImportSpec)
		if importPath(impspec) > path {
			insertAt = i
			break
		}
	}

	impdecl.Specs = append(impdecl.Specs, nil)
	copy(impdecl.Specs[insertAt+1:], impdecl.Specs[insertAt:])
	impdecl.Specs[insertAt] = newImport

	f.Imports = append(f.Imports, newImport)
}

// importsToDecl turns Lisp import into Go AST
func importsToDecl(specs []ast.Spec) ast.Decl {
	s := ast.GenDecl{
		Doc:   genComment(),
		Tok:   token.IMPORT,
		Specs: specs,
	}
	// https://godoc.org/go/ast#GenDecl
	// A valid Lparen position (Lparen.Line > 0) indicates a parenthesized declaration.
	s.Lparen = 1
	return &s
}

func genSnippet(fset *token.FileSet, d *ast.GenDecl, id *ast.Ident) *Snippet {
	s := findSpec(d.Specs, id)
	if s == nil {
		return nil //  declaration doesn't contain id - exit gracefully
	}

	// only use the spec containing the id for the snippet
	dd := &ast.GenDecl{d.Doc, d.Pos(), d.Tok, d.Lparen, []ast.Spec{s}, d.Rparen}

	return newSnippet(fset, dd, id)
}

func isEmpty(f *ast.File, g *ast.GenDecl) bool {
	if g.Doc != nil || g.Specs != nil {
		return false
	}

	for _, c := range f.Comments {
		// if there is a comment in the declaration, it is not considered empty
		if g.Pos() <= c.Pos() && c.End() <= g.End() {
			return false
		}
	}

	return true
}

func (p *printer) genDecl(d *ast.GenDecl) {
	p.setComment(d.Doc)
	p.print(d.Pos(), d.Tok, blank)

	if d.Lparen.IsValid() {
		// group of parenthesized declarations
		p.print(d.Lparen, token.LPAREN)
		if n := len(d.Specs); n > 0 {
			p.print(indent, formfeed)
			if n > 1 && (d.Tok == token.CONST || d.Tok == token.VAR) {
				// two or more grouped const/var declarations:
				// determine if the type column must be kept
				keepType := keepTypeColumn(d.Specs)
				var line int
				for i, s := range d.Specs {
					if i > 0 {
						p.linebreak(p.lineFor(s.Pos()), 1, ignore, p.linesFrom(line) > 0)
					}
					p.recordLine(&line)
					switch t := s.(type) {
					case *ast.AliasSpec:
						p.aliasSpec(t, keepType[i])

					case *ast.ValueSpec:
						p.valueSpec(t, keepType[i])

					default:
						p.internalError("unknown ast.Spec type: %T", t)
					}
				}
			} else {
				var line int
				for i, s := range d.Specs {
					if i > 0 {
						p.linebreak(p.lineFor(s.Pos()), 1, ignore, p.linesFrom(line) > 0)
					}
					p.recordLine(&line)
					p.spec(s, n, false)
				}
			}
			p.print(unindent, formfeed)
		}
		p.print(d.Rparen, token.RPAREN)

	} else {
		// single declaration
		p.spec(d.Specs[0], 1, true)
	}
}

// assocInitvals associates "inherited" initialization expressions
// with the corresponding *ast.ValueSpec in the check.initexprs map
// for constant declarations without explicit initialization expressions.
//
func (check *checker) assocInitvals(decl *ast.GenDecl) {
	var values []ast.Expr
	for _, s := range decl.Specs {
		if s, ok := s.(*ast.ValueSpec); ok {
			if len(s.Values) > 0 {
				values = s.Values
			} else {
				check.initexprs[s] = values
			}
		}
	}
	if len(values) == 0 {
		check.invalidAST(decl.Pos(), "no initialization values provided")
	}
}

// assocInitvals associates "inherited" initialization expressions
// with the corresponding *ast.ValueSpec in the check.initspecs map
// for constant declarations without explicit initialization expressions.
//
func (check *checker) assocInitvals(decl *ast.GenDecl) {
	var last *ast.ValueSpec
	for _, s := range decl.Specs {
		if s, ok := s.(*ast.ValueSpec); ok {
			if len(s.Values) > 0 {
				last = s
			} else {
				check.initspecs[s] = last
			}
		}
	}
	if last == nil {
		check.invalidAST(decl.Pos(), "no initialization values provided")
	}
}

// readType processes a type declaration.
//
func (r *reader) readType(decl *ast.GenDecl, spec *ast.TypeSpec) {
	typ := r.lookupType(spec.Name.Name)
	if typ == nil {
		return // no name or blank name - ignore the type
	}

	// A type should be added at most once, so typ.decl
	// should be nil - if it is not, simply overwrite it.
	typ.decl = decl

	// compute documentation
	doc := spec.Doc
	spec.Doc = nil // doc consumed - remove from AST
	if doc == nil {
		// no doc associated with the spec, use the declaration doc, if any
		doc = decl.Doc
	}
	decl.Doc = nil // doc consumed - remove from AST
	typ.doc = doc.Text()

	// record anonymous fields (they may contribute methods)
	// (some fields may have been recorded already when filtering
	// exports, but that's ok)
	var list []*ast.Field
	list, typ.isStruct = fields(spec.Type)
	for _, field := range list {
		if len(field.Names) == 0 {
			r.recordAnonymousField(typ, field.Type)
		}
	}
}

func ast_decl_split(d ast.Decl) []ast.Decl {
	var decls []ast.Decl
	if t, ok := d.(*ast.GenDecl); ok {
		decls = make([]ast.Decl, len(t.Specs))
		for i, s := range t.Specs {
			decl := new(ast.GenDecl)
			*decl = *t
			decl.Specs = make([]ast.Spec, 1)
			decl.Specs[0] = s
			decls[i] = decl
		}
	} else {
		decls = make([]ast.Decl, 1)
		decls[0] = d
	}
	return decls
}

func (p *Presentation) genSnippet(fset *token.FileSet, d *ast.GenDecl, id *ast.Ident) *Snippet {
	s := findSpec(d.Specs, id)
	if s == nil {
		return nil //  declaration doesn't contain id - exit gracefully
	}

	// only use the spec containing the id for the snippet
	dd := &ast.GenDecl{
		Doc:    d.Doc,
		TokPos: d.Pos(),
		Tok:    d.Tok,
		Lparen: d.Lparen,
		Specs:  []ast.Spec{s},
		Rparen: d.Rparen,
	}

	return p.newSnippet(fset, dd, id)
}

// Sets multiLine to true if the declaration spans multiple lines.
func (p *printer) genDecl(d *ast.GenDecl, multiLine *bool) {
	p.setComment(d.Doc)
	p.print(d.Pos(), d.Tok, blank)

	if d.Lparen.IsValid() {
		// group of parenthesized declarations
		p.print(d.Lparen, token.LPAREN)
		if n := len(d.Specs); n > 0 {
			p.print(indent, formfeed)
			if n > 1 && (d.Tok == token.CONST || d.Tok == token.VAR) {
				// two or more grouped const/var declarations:
				// determine if the type column must be kept
				keepType := keepTypeColumn(d.Specs)
				var ml bool
				for i, s := range d.Specs {
					if i > 0 {
						p.linebreak(p.fset.Position(s.Pos()).Line, 1, ignore, ml)
					}
					ml = false
					p.valueSpec(s.(*ast.ValueSpec), keepType[i], false, &ml)
				}
			} else {
				var ml bool
				for i, s := range d.Specs {
					if i > 0 {
						p.linebreak(p.fset.Position(s.Pos()).Line, 1, ignore, ml)
					}
					ml = false
					p.spec(s, n, false, &ml)
				}
			}
			p.print(unindent, formfeed)
			*multiLine = true
		}
		p.print(d.Rparen, token.RPAREN)

	} else {
		// single declaration
		p.spec(d.Specs[0], 1, true, multiLine)
	}
}

func (p *printer) genDecl(d *ast.GenDecl) {
	p.setComment(d.Doc)
	p.print(d.Pos(), d.Tok, blank)

	if d.Lparen.IsValid() {
		// group of parenthesized declarations
		p.print(d.Lparen, token.LPAREN)
		if n := len(d.Specs); n > 0 {
			p.print(indent, formfeed)
			if n > 1 && (d.Tok == token.CONST || d.Tok == token.VAR) {
				// two or more grouped const/var declarations:
				// determine if the type column must be kept
				keepType := keepTypeColumn(d.Specs)
				newSection := false
				for i, s := range d.Specs {
					if i > 0 {
						p.linebreak(p.lineFor(s.Pos()), 1, ignore, newSection)
					}
					p.valueSpec(s.(*ast.ValueSpec), keepType[i], false)
					newSection = p.isMultiLine(s)
				}
			} else {
				newSection := false
				for i, s := range d.Specs {
					if i > 0 {
						p.linebreak(p.lineFor(s.Pos()), 1, ignore, newSection)
					}
					p.spec(s, n, false)
					newSection = p.isMultiLine(s)
				}
			}
			p.print(unindent, formfeed)
		}
		p.print(d.Rparen, token.RPAREN)

	} else {
		// single declaration
		p.spec(d.Specs[0], 1, true)
	}
}

func newValue(decl *ast.GenDecl) *Value {
	v := new(Value)
	v.Doc = doc.CommentText(decl.Doc)
	decl.Doc = nil

	// count names and figure out type
	n := 0
	for _, spec := range decl.Specs {
		vspec := spec.(*ast.ValueSpec)
		for _, name := range vspec.Names {
			if ast.IsExported(name.Name) {
				n++
			}
		}

		if v.Type == "" {
			t := typeAsString(vspec.Type)
			if t != "" && ast.IsExported(t) {
				v.Type = t
			}
		}
	}

	if n == 0 {
		return nil
	}

	// collect names
	v.Names = make([]string, n)

	i := 0
	for _, spec := range decl.Specs {
		vspec := spec.(*ast.ValueSpec)
		for _, name := range vspec.Names {
			if !ast.IsExported(name.Name) {
				continue
			}
			v.Names[i] = name.Name
			i++
		}
	}

	v.Decl = decl
	return v
}

// readType processes a type declaration.
//
func (r *reader) readType(decl *ast.GenDecl, spec *ast.TypeSpec) {
	typ := r.lookupType(spec.Name.Name)
	if typ == nil {
		return // no name or blank name - ignore the type
	}

	// A type should be added at most once, so info.decl
	// should be nil - if it is not, simply overwrite it.
	typ.decl = decl

	// compute documentation
	doc := spec.Doc
	spec.Doc = nil // doc consumed - remove from AST
	if doc == nil {
		// no doc associated with the spec, use the declaration doc, if any
		doc = decl.Doc
	}
	decl.Doc = nil // doc consumed - remove from AST
	typ.doc = doc.Text()

	// look for anonymous fields that might contribute methods
	var list []*ast.Field
	list, typ.isStruct = fields(spec.Type)
	for _, field := range list {
		if len(field.Names) == 0 {
			// anonymous field - add corresponding field type to typ
			n, imp := baseTypeName(field.Type)
			if imp {
				// imported type - we don't handle this case
				// at the moment
				return
			}
			if embedded := r.lookupType(n); embedded != nil {
				_, ptr := field.Type.(*ast.StarExpr)
				typ.addEmbeddedType(embedded, ptr)
			}
		}
	}
}

// oneLineValueGenDecl prints a var or const declaration as a single line.
func (pkg *Package) oneLineValueGenDecl(decl *ast.GenDecl) {
	decl.Doc = nil
	dotDotDot := ""
	if len(decl.Specs) > 1 {
		dotDotDot = " ..."
	}
	// Find the first relevant spec.
	for i, spec := range decl.Specs {
		valueSpec := spec.(*ast.ValueSpec) // Must succeed; we can't mix types in one genDecl.
		if !isExported(valueSpec.Names[0].Name) {
			continue
		}
		typ := ""
		if valueSpec.Type != nil {
			typ = fmt.Sprintf(" %s", pkg.formatNode(valueSpec.Type))
		}
		val := ""
		if i < len(valueSpec.Values) && valueSpec.Values[i] != nil {
			val = fmt.Sprintf(" = %s", pkg.formatNode(valueSpec.Values[i]))
		}
		pkg.Printf("%s %s%s%s%s\n", decl.Tok, valueSpec.Names[0], typ, val, dotDotDot)
		break
	}
}

// AddNamedImport adds the import path to the file f, if absent.
// If name is not empty, it is used to rename the import.
//
// For example, calling
//	AddNamedImport(fset, f, "pathpkg", "path")
// adds
//	import pathpkg "path"
func AddNamedImport(fset *token.FileSet, f *ast.File, name, ipath string) (added bool) {
	if imports(f, ipath) {
		return false
	}

	newImport := &ast.ImportSpec{
		Path: &ast.BasicLit{
			Kind:  token.STRING,
			Value: strconv.Quote(ipath),
		},
	}
	if name != "" {
		newImport.Name = &ast.Ident{Name: name}
	}

	// Find an import decl to add to.
	var (
		bestMatch  = -1
		lastImport = -1
		impDecl    *ast.GenDecl
		impIndex   = -1
		hasImports = false
	)
	for i, decl := range f.Decls {
		gen, ok := decl.(*ast.GenDecl)
		if ok && gen.Tok == token.IMPORT {
			hasImports = true
			lastImport = i
			// Do not add to import "C", to avoid disrupting the
			// association with its doc comment, breaking cgo.
			if declImports(gen, "C") {
				continue
			}

			// Compute longest shared prefix with imports in this block.
			for j, spec := range gen.Specs {
				impspec := spec.(*ast.ImportSpec)
				n := matchLen(importPath(impspec), ipath)
				if n > bestMatch {
					bestMatch = n
					impDecl = gen
					impIndex = j
				}
			}
		}
	}

	// If no import decl found, add one after the last import.
	if impDecl == nil {
		// TODO(bradfitz): remove this hack. See comment below on
		// addImportViaSourceModification.
		if !hasImports {
			f2, err := addImportViaSourceModification(fset, f, name, ipath)
			if err == nil {
				*f = *f2
				return true
			}
			log.Printf("addImportViaSourceModification error: %v", err)
		}

		// TODO(bradfitz): fix above and resume using this old code:
		impDecl = &ast.GenDecl{
			Tok: token.IMPORT,
		}
		f.Decls = append(f.Decls, nil)
		copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
		f.Decls[lastImport+1] = impDecl
	}

	// Ensure the import decl has parentheses, if needed.
	if len(impDecl.Specs) > 0 && !impDecl.Lparen.IsValid() {
		impDecl.Lparen = impDecl.Pos()
	}

	insertAt := impIndex + 1
	if insertAt == 0 {
		insertAt = len(impDecl.Specs)
	}
	impDecl.Specs = append(impDecl.Specs, nil)
	copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
	impDecl.Specs[insertAt] = newImport
	if insertAt > 0 {
		// Assign same position as the previous import,
		// so that the sorter sees it as being in the same block.
		prev := impDecl.Specs[insertAt-1]
		newImport.Path.ValuePos = prev.Pos()
		newImport.EndPos = prev.Pos()
	}
	if len(impDecl.Specs) > 1 && impDecl.Lparen == 0 {
		// set Lparen to something not zero, so the printer prints
		// the full block rather just the first ImportSpec.
		impDecl.Lparen = 1
	}
//.........这里部分代码省略.........

// TODO(bradfitz): delete this function (and whole file) once
// http://golang.org/issue/4380 is fixed.
func clone(i interface{}) (cloned interface{}) {
	if debugClone {
		defer func() {
			if !reflect.DeepEqual(i, cloned) {
				log.Printf("cloned %T doesn't match: in=%#v out=%#v", i, i, cloned)
			}
		}()
	}
	switch v := i.(type) {
	case nil:
		return nil
	case *ast.File:
		o := &ast.File{
			Doc:      v.Doc, // shallow
			Package:  v.Package,
			Comments: v.Comments, // shallow
			Name:     v.Name,
			Scope:    v.Scope,
		}
		for _, x := range v.Decls {
			o.Decls = append(o.Decls, clone(x).(ast.Decl))
		}
		for _, x := range v.Imports {
			o.Imports = append(o.Imports, clone(x).(*ast.ImportSpec))
		}
		for _, x := range v.Unresolved {
			o.Unresolved = append(o.Unresolved, x)
		}
		return o
	case *ast.GenDecl:
		o := new(ast.GenDecl)
		*o = *v
		o.Specs = nil
		for _, x := range v.Specs {
			o.Specs = append(o.Specs, clone(x).(ast.Spec))
		}
		return o
	case *ast.TypeSpec:
		o := new(ast.TypeSpec)
		*o = *v
		o.Type = cloneExpr(v.Type)
		return o
	case *ast.InterfaceType:
		o := new(ast.InterfaceType)
		*o = *v
		o.Methods = clone(v.Methods).(*ast.FieldList)
		return o
	case *ast.FieldList:
		if v == nil {
			return v
		}
		o := new(ast.FieldList)
		*o = *v
		o.List = nil
		for _, x := range v.List {
			o.List = append(o.List, clone(x).(*ast.Field))
		}
		return o
	case *ast.Field:
		o := &ast.Field{
			Doc:     v.Doc, // shallow
			Type:    cloneExpr(v.Type),
			Tag:     clone(v.Tag).(*ast.BasicLit),
			Comment: v.Comment, // shallow
		}
		for _, x := range v.Names {
			o.Names = append(o.Names, clone(x).(*ast.Ident))
		}
		return o
	case *ast.FuncType:
		if v == nil {
			return v
		}
		return &ast.FuncType{
			Func:    v.Func,
			Params:  clone(v.Params).(*ast.FieldList),
			Results: clone(v.Results).(*ast.FieldList),
		}
	case *ast.FuncDecl:
		if v == nil {
			return v
		}
		return &ast.FuncDecl{
			Recv: clone(v.Recv).(*ast.FieldList),
			Name: v.Name,
			Type: clone(v.Type).(*ast.FuncType),
			Body: v.Body, // shallow
		}
	case *ast.ValueSpec:
		if v == nil {
			return v
		}
		o := &ast.ValueSpec{
			Type: cloneExpr(v.Type),
		}
		for _, x := range v.Names {
			o.Names = append(o.Names, x)
		}
//.........这里部分代码省略.........

// AddNamedImport adds the import path to the file f, if absent.
// If name is not empty, it is used to rename the import.
//
// For example, calling
//	AddNamedImport(fset, f, "pathpkg", "path")
// adds
//	import pathpkg "path"
func AddNamedImport(fset *token.FileSet, f *ast.File, name, ipath string) (added bool) {
	if imports(f, ipath) {
		return false
	}

	newImport := &ast.ImportSpec{
		Path: &ast.BasicLit{
			Kind:  token.STRING,
			Value: strconv.Quote(ipath),
		},
	}
	if name != "" {
		newImport.Name = &ast.Ident{Name: name}
	}

	// Find an import decl to add to.
	// The goal is to find an existing import
	// whose import path has the longest shared
	// prefix with ipath.
	var (
		bestMatch  = -1         // length of longest shared prefix
		lastImport = -1         // index in f.Decls of the file's final import decl
		impDecl    *ast.GenDecl // import decl containing the best match
		impIndex   = -1         // spec index in impDecl containing the best match
	)
	for i, decl := range f.Decls {
		gen, ok := decl.(*ast.GenDecl)
		if ok && gen.Tok == token.IMPORT {
			lastImport = i
			// Do not add to import "C", to avoid disrupting the
			// association with its doc comment, breaking cgo.
			if declImports(gen, "C") {
				continue
			}

			// Match an empty import decl if that's all that is available.
			if len(gen.Specs) == 0 && bestMatch == -1 {
				impDecl = gen
			}

			// Compute longest shared prefix with imports in this group.
			for j, spec := range gen.Specs {
				impspec := spec.(*ast.ImportSpec)
				n := matchLen(importPath(impspec), ipath)
				if n > bestMatch {
					bestMatch = n
					impDecl = gen
					impIndex = j
				}
			}
		}
	}

	// If no import decl found, add one after the last import.
	if impDecl == nil {
		impDecl = &ast.GenDecl{
			Tok: token.IMPORT,
		}
		if lastImport >= 0 {
			impDecl.TokPos = f.Decls[lastImport].End()
		} else {
			// There are no existing imports.
			// Our new import goes after the package declaration and after
			// the comment, if any, that starts on the same line as the
			// package declaration.
			impDecl.TokPos = f.Package

			file := fset.File(f.Package)
			pkgLine := file.Line(f.Package)
			for _, c := range f.Comments {
				if file.Line(c.Pos()) > pkgLine {
					break
				}
				impDecl.TokPos = c.End()
			}
		}
		f.Decls = append(f.Decls, nil)
		copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
		f.Decls[lastImport+1] = impDecl
	}

	// Insert new import at insertAt.
	insertAt := 0
	if impIndex >= 0 {
		// insert after the found import
		insertAt = impIndex + 1
	}
	impDecl.Specs = append(impDecl.Specs, nil)
	copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
	impDecl.Specs[insertAt] = newImport
	pos := impDecl.Pos()
	if insertAt > 0 {
		// If there is a comment after an existing import, preserve the comment
//.........这里部分代码省略.........