bug fix: convert \v's into \t's if there's no tabwriter

R=rsc
DELTA=15  (12 added, 2 deleted, 1 changed)
OCL=35641
CL=35645

src/pkg/go/printer/printer.go

@@ -356,7 +356,6 @@ func (p *printer) writeComment(comment *ast.Comment) {
 }
 
 
-
 // writeCommentSuffix writes a line break after a comment if indicated
 // and processes any leftover indentation information. If a line break
 // is needed, the kind of break (newline vs formfeed) depends on the
@@ -388,7 +387,6 @@ func (p *printer) writeCommentSuffix(needsLinebreak bool) {
 }
 
 
-
 // intersperseComments consumes all comments that appear before the next token
 // and prints it together with the buffered whitespace (i.e., the whitespace
 // that needs to be written before the next token). A heuristic is used to mix
@@ -978,6 +976,7 @@ func (p *printer) expr1(expr ast.Expr, prec1 int) (optSemi bool) {
 		}
 
 	case *ast.BasicLit:
+		// TODO(gri): string contents must remain unchanged through tabwriter!
 		p.print(x.Value);
 
 	case *ast.StringList:
@@ -1535,7 +1534,8 @@ func (p *printer) file(src *ast.File) {
 // Trimmer
 
 // A trimmer is an io.Writer filter for stripping trailing blanks
-// and tabs, and for converting formfeed characters into newlines.
+// and tabs, and for converting formfeed and vtab characters into
+// newlines and htabs (in case no tabwriter is used).
 //
 type trimmer struct {
 	output io.Writer;
@@ -1543,6 +1543,12 @@ type trimmer struct {
 }
 
 
+// Design note: It is tempting to eliminate extra blanks occuring in
+//              whitespace in this function as it could simplify some
+//              of the blanks logic in the node printing functions.
+//              However, this would mess up any formatting done by
+//              the tabwriter.
+
 func (p *trimmer) Write(data []byte) (n int, err os.Error) {
 	// m < 0: no unwritten data except for whitespace
 	// m >= 0: data[m:n] unwritten and no whitespace
@@ -1564,6 +1570,10 @@ func (p *trimmer) Write(data []byte) (n int, err os.Error) {
 				m = n;
 			}
 
+		case '\v':
+			b = '\t';  // convert to htab
+			fallthrough;
+
 		case '\t', ' ':
 			// write any pending (non-whitespace) data
 			if m >= 0 {