go/parser cleanup: remove some state by writing more functional code

R=rsc
CC=golang-dev
https://golang.org/cl/223071

diff --git a/src/pkg/go/parser/parser.go b/src/pkg/go/parser/parser.go
index fd215f0d9e981de0067bc41674d5429d69a5edcc..9928496e6c8b172e1f52633b2de2d3ccd08ae1d6 100644 (file)
--- a/src/pkg/go/parser/parser.go
+++ b/src/pkg/go/parser/parser.go
@@ -46,7 +46,6 @@ type parser struct {
 
        // 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
 
@@ -163,13 +162,13 @@ func (p *parser) consumeComment() (comment *ast.Comment, endline int) {
 
 
 // Consume a group of adjacent comments, add it to the parser's
-// comments list, and return the line of which the last comment
-// in the group ends. An empty line or non-comment token terminates
-// a comment group.
+// comments list, and return it together with the line at which
+// the last comment in the group ends. An empty line or non-comment
+// token terminates a comment group.
 //
-func (p *parser) consumeCommentGroup() int {
+func (p *parser) consumeCommentGroup() (comments *ast.CommentGroup, endline int) {
        var list vector.Vector
-       endline := p.pos.Line
+       endline = p.pos.Line
        for p.tok == token.COMMENT && endline+1 >= p.pos.Line {
                var comment *ast.Comment
                comment, endline = p.consumeComment()
@@ -183,11 +182,10 @@ func (p *parser) consumeCommentGroup() int {
        }
 
        // add comment group to the comments list
-       g := &ast.CommentGroup{group}
-       p.comments.Push(g)
-       p.lastComment = g
+       comments = &ast.CommentGroup{group}
+       p.comments.Push(comments)
 
-       return endline
+       return
 }
 
 
@@ -213,27 +211,30 @@ func (p *parser) next() {
        p.next0()
 
        if p.tok == token.COMMENT {
+               var comment *ast.CommentGroup
+               var endline int
+
                if p.pos.Line == line {
                        // The comment is on same line as previous token; it
                        // cannot be a lead comment but may be a line comment.
-                       endline := p.consumeCommentGroup()
+                       comment, endline = p.consumeCommentGroup()
                        if p.pos.Line != endline {
                                // The next token is on a different line, thus
                                // the last comment group is a line comment.
-                               p.lineComment = p.lastComment
+                               p.lineComment = comment
                        }
                }
 
                // consume successor comments, if any
-               endline := -1
+               endline = -1
                for p.tok == token.COMMENT {
-                       endline = p.consumeCommentGroup()
+                       comment, endline = p.consumeCommentGroup()
                }
 
-               if endline >= 0 && endline+1 == p.pos.Line {
+               if endline+1 == p.pos.Line {
                        // The next token is following on the line immediately after the
                        // comment group, thus the last comment group is a lead comment.
-                       p.leadComment = p.lastComment
+                       p.leadComment = comment
                }
        }
 }