go/ast: use a slice instead of a linked list for the list of comments

(this will simplify some further changes)
removed several TODOs

R=rsc
CC=golang-dev
https://golang.org/cl/216059

src/pkg/go/ast/ast.go

@@ -75,7 +75,6 @@ type Comment struct {
 //
 type CommentGroup struct {
 	List []*Comment
-	Next *CommentGroup // next comment group in source order
 }
 
 
@@ -695,12 +694,16 @@ func (d *FuncDecl) declNode() {}
 
 // A File node represents a Go source file.
 //
+// The Comments list contains all comments in the source file in order of
+// appearance, including the comments that are pointed to from other nodes
+// via Doc and Comment fields.
+//
 type File struct {
 	Doc            *CommentGroup   // associated documentation; or nil
 	token.Position                 // position of "package" keyword
 	Name           *Ident          // package name
 	Decls          []Decl          // top-level declarations
-	Comments       *CommentGroup // list of all comments in the source file
+	Comments       []*CommentGroup // list of all comments in the source file
 }
 
 

src/pkg/go/ast/filter.go

@@ -107,8 +107,6 @@ func filterSpec(spec Spec) bool {
 			return true
 		}
 	case *TypeSpec:
-		// TODO(gri) consider stripping forward declarations
-		//           of structs, interfaces, functions, and methods
 		if s.Name.IsExported() {
 			filterType(s.Type)
 			return true
@@ -136,9 +134,6 @@ func filterDecl(decl Decl) bool {
 		d.Specs = filterSpecList(d.Specs)
 		return len(d.Specs) > 0
 	case *FuncDecl:
-		// TODO consider removing function declaration altogether if
-		//      forward declaration (i.e., if d.Body == nil) because
-		//      in that case the actual declaration will come later.
 		d.Body = nil // strip body
 		return d.Name.IsExported()
 	}
@@ -230,7 +225,7 @@ func MergePackageFiles(pkg *Package) *File {
 				}
 			}
 		}
-		doc = &CommentGroup{list, nil}
+		doc = &CommentGroup{list}
 	}
 
 	// Collect declarations from all package files.
@@ -246,8 +241,6 @@ func MergePackageFiles(pkg *Package) *File {
 		}
 	}
 
-	// TODO(gri) Should collect comments as well. For that the comment
+	// TODO(gri) Should collect comments as well.
-	//           list should be changed back into a []*CommentGroup,
-	//           otherwise need to modify the existing linked list.
 	return &File{doc, noPos, NewIdent(pkg.Name), decls, nil}
 }

src/pkg/go/ast/walk.go

@@ -64,11 +64,6 @@ func Walk(v Visitor, node interface{}) {
 		for _, c := range n.List {
 			Walk(v, c)
 		}
-		// TODO(gri): Keep comments in a list/vector instead
-		// of linking them via Next. Following next will lead
-		// to multiple visits and potentially n^2 behavior
-		// since Doc and Comments fields point into the global
-		// comments list.
 
 	case *Field:
 		walkCommentGroup(v, n.Doc)
@@ -283,7 +278,9 @@ func Walk(v Visitor, node interface{}) {
 		walkCommentGroup(v, n.Doc)
 		walkIdent(v, n.Name)
 		Walk(v, n.Decls)
-		walkCommentGroup(v, n.Comments)
+		for _, g := range n.Comments {
+			Walk(v, g)
+		}
 
 	case *Package:
 		for _, f := range n.Files {

src/pkg/go/doc/doc.go

@@ -272,7 +272,7 @@ func (doc *docReader) addFile(src *ast.File) {
 	}
 
 	// collect BUG(...) comments
-	for c := src.Comments; c != nil; c = c.Next {
+	for _, c := range src.Comments {
 		text := c.List[0].Text
 		cstr := string(text)
 		if m := bug_markers.ExecuteString(cstr); len(m) > 0 {
@@ -281,7 +281,7 @@ func (doc *docReader) addFile(src *ast.File) {
 				// non-empty BUG comment; collect comment without BUG prefix
 				list := copyCommentList(c.List)
 				list[0].Text = text[m[1]:]
-				doc.bugs.Push(&ast.CommentGroup{list, nil})
+				doc.bugs.Push(&ast.CommentGroup{list})
 			}
 		}
 	}

src/pkg/go/parser/parser.go

@@ -45,7 +45,7 @@ type parser struct {
 	indent uint // indentation used for tracing output
 
 	// Comments
-	comments    *ast.CommentGroup // list of collected comments
+	comments    vector.Vector     // list of *CommentGroup
 	lastComment *ast.CommentGroup // last comment in the comments list
 	leadComment *ast.CommentGroup // the last lead comment
 	lineComment *ast.CommentGroup // the last line comment
@@ -183,12 +183,8 @@ func (p *parser) consumeCommentGroup() int {
 	}
 
 	// add comment group to the comments list
-	g := &ast.CommentGroup{group, nil}
+	g := &ast.CommentGroup{group}
-	if p.lastComment != nil {
+	p.comments.Push(g)
-		p.lastComment.Next = g
-	} else {
-		p.comments = g
-	}
 	p.lastComment = g
 
 	return endline
@@ -2095,5 +2091,11 @@ func (p *parser) parseFile() *ast.File {
 		}
 	}
 
-	return &ast.File{doc, pos, ident, decls, p.comments}
+	// convert comments list
+	comments := make([]*ast.CommentGroup, len(p.comments))
+	for i, x := range p.comments {
+		comments[i] = x.(*ast.CommentGroup)
+	}
+
+	return &ast.File{doc, pos, ident, decls, comments}
 }

src/pkg/go/printer/nodes.go

@@ -88,7 +88,7 @@ func (p *printer) commentList(list []*ast.Comment) {
 // Print a lead comment followed by a newline.
 func (p *printer) leadComment(d *ast.CommentGroup) {
 	// Ignore the comment if we have comments interspersed (p.comment != nil).
-	if p.comment == nil && d != nil {
+	if p.comments == nil && d != nil {
 		p.commentList(d.List)
 		p.print(newline)
 	}
@@ -100,7 +100,7 @@ func (p *printer) leadComment(d *ast.CommentGroup) {
 // the comment may be a //-style comment.
 func (p *printer) lineComment(d *ast.CommentGroup) {
 	// Ignore the comment if we have comments interspersed (p.comment != nil).
-	if p.comment == nil && d != nil {
+	if p.comments == nil && d != nil {
 		p.print(vtab)
 		p.commentList(d.List)
 	}
@@ -152,8 +152,8 @@ const (
 // Remove this after transitioning to new semicolon syntax and
 // some reasonable grace period (12/11/09).
 func (p *printer) beforeComment(pos token.Position) token.Position {
-	if p.comment != nil {
+	if p.cindex < len(p.comments) {
-		p := p.comment.List[0].Position
+		p := p.comments[p.cindex].List[0].Position
 		if !pos.IsValid() || pos.Offset > p.Offset {
 			return p
 		}
@@ -852,7 +852,7 @@ func (p *printer) moveCommentsAfter(pos token.Position) {
 	//            Remove this after transitioning to new semicolon
 	//            syntax and some reasonable grace period (12/11/09).
 	if p.commentBefore(pos) {
-		p.comment.List[0].Position = pos
+		p.comments[p.cindex].List[0].Position = pos
 	}
 }
 

src/pkg/go/printer/printer.go

@@ -88,8 +88,9 @@ type printer struct {
 	// HTML support
 	lastTaggedLine int // last line for which a line tag was written
 
-	// The list of comments; or nil.
+	// The list of all source comments, in order of appearance.
-	comment *ast.CommentGroup
+	comments []*ast.CommentGroup // may be nil
+	cindex   int                 // current comment index
 }
 
 
@@ -624,8 +625,8 @@ func (p *printer) intersperseComments(next token.Position, isKeyword bool) {
 	isFirst := true
 	needsLinebreak := false
 	var last *ast.Comment
-	for ; p.commentBefore(next); p.comment = p.comment.Next {
+	for ; p.commentBefore(next); p.cindex++ {
-		for _, c := range p.comment.List {
+		for _, c := range p.comments[p.cindex].List {
 			p.writeCommentPrefix(c.Pos(), next, isFirst, isKeyword)
 			isFirst = false
 			p.writeComment(c)
@@ -792,7 +793,7 @@ func (p *printer) print(args ...) {
 // before the next position in the source code.
 //
 func (p *printer) commentBefore(next token.Position) bool {
-	return p.comment != nil && p.comment.List[0].Pos().Offset < next.Offset
+	return p.cindex < len(p.comments) && p.comments[p.cindex].List[0].Pos().Offset < next.Offset
 }
 
 
@@ -981,7 +982,7 @@ func (cfg *Config) Fprint(output io.Writer, node interface{}) (int, os.Error) {
 		case ast.Decl:
 			p.decl(n, atTop, ignoreMultiLine)
 		case *ast.File:
-			p.comment = n.Comments
+			p.comments = n.Comments
 			p.file(n)
 		default:
 			p.errors <- os.NewError(fmt.Sprintf("printer.Fprint: unsupported node type %T", n))