libgo: Update to weekly.2011-12-22.

From-SVN: r183150

7 files changed, 154 insertions, 74 deletions

diff --git a/libgo/go/go/printer/nodes.go b/libgo/go/go/printer/nodes.go
index b2a48c28a73..6817cc42add 100644
--- a/libgo/go/go/printer/nodes.go
+++ b/libgo/go/go/printer/nodes.go
@@ -39,7 +39,10 @@ import (
 //            future (not yet interspersed) comments in this function.
 //
 func (p *printer) linebreak(line, min int, ws whiteSpace, newSection bool) (printedBreak bool) {
-	n := p.nlines(line-p.pos.Line, min)
+	n := nlimit(line - p.pos.Line)
+	if n < min {
+		n = min
+	}
 	if n > 0 {
 		p.print(ws)
 		if newSection {
@@ -361,9 +364,10 @@ func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool)
 	lbrace := fields.Opening
 	list := fields.List
 	rbrace := fields.Closing
+	hasComments := isIncomplete || p.commentBefore(p.fset.Position(rbrace))
 	srcIsOneLine := lbrace.IsValid() && rbrace.IsValid() && p.fset.Position(lbrace).Line == p.fset.Position(rbrace).Line
 
-	if !isIncomplete && !p.commentBefore(p.fset.Position(rbrace)) && srcIsOneLine {
+	if !hasComments && srcIsOneLine {
 		// possibly a one-line struct/interface
 		if len(list) == 0 {
 			// no blank between keyword and {} in this case
@@ -388,9 +392,13 @@ func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool)
 			return
 		}
 	}
+	// hasComments || !srcIsOneLine
+
+	p.print(blank, lbrace, token.LBRACE, indent)
+	if hasComments || len(list) > 0 {
+		p.print(formfeed)
+	}
 
-	// at least one entry or incomplete
-	p.print(blank, lbrace, token.LBRACE, indent, formfeed)
 	if isStruct {
 
 		sep := vtab
@@ -1509,9 +1517,14 @@ func (p *printer) file(src *ast.File) {
 			prev := tok
 			tok = declToken(d)
 			// if the declaration token changed (e.g., from CONST to TYPE)
+			// or the next declaration has documentation associated with it,
 			// print an empty line between top-level declarations
+			// (because p.linebreak is called with the position of d, which
+			// is past any documentation, the minimum requirement is satisfied
+			// even w/o the extra getDoc(d) nil-check - leave it in case the
+			// linebreak logic improves - there's already a TODO).
 			min := 1
-			if prev != tok {
+			if prev != tok || getDoc(d) != nil {
 				min = 2
 			}
 			p.linebreak(p.fset.Position(d.Pos()).Line, min, ignore, false)
diff --git a/libgo/go/go/printer/printer.go b/libgo/go/go/printer/printer.go
index 8538236c2c9..a78cfc65fcc 100644
--- a/libgo/go/go/printer/printer.go
+++ b/libgo/go/go/printer/printer.go
@@ -18,8 +18,11 @@ import (
 	"text/tabwriter"
 )
 
-const debug = false // enable for debugging
-const infinity = 1 << 30
+const (
+	maxNewlines = 2     // max. number of newlines between source text
+	debug       = false // enable for debugging
+	infinity    = 1 << 30
+)
 
 type whiteSpace byte
 
@@ -89,21 +92,7 @@ func (p *printer) internalError(msg ...interface{}) {
 	}
 }
 
-// nlines returns the adjusted number of linebreaks given the desired number
-// of breaks n such that min <= result <= max.
-//
-func (p *printer) nlines(n, min int) int {
-	const max = 2 // max. number of newlines
-	switch {
-	case n < min:
-		return min
-	case n > max:
-		return max
-	}
-	return n
-}
-
-// writeByte writes a single byte to p.output and updates p.pos.
+// writeByte writes ch to p.output and updates p.pos.
 func (p *printer) writeByte(ch byte) {
 	p.output.WriteByte(ch)
 	p.pos.Offset++
@@ -128,13 +117,11 @@ func (p *printer) writeByte(ch byte) {
 	}
 }
 
-// writeNewlines writes up to n newlines to p.output and updates p.pos.
-// The actual number of newlines written is limited by nlines.
-// nl must be one of '\n' or '\f'.
-//
-func (p *printer) writeNewlines(n int, nl byte) {
-	for n = p.nlines(n, 0); n > 0; n-- {
-		p.writeByte(nl)
+// writeByteN writes ch n times to p.output and updates p.pos.
+func (p *printer) writeByteN(ch byte, n int) {
+	for n > 0 {
+		p.writeByte(ch)
+		n--
 	}
 }
 
@@ -223,8 +210,8 @@ func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *as
 	}
 
 	if pos.IsValid() && pos.Filename != p.last.Filename {
-		// comment in a different file - separate with newlines (writeNewlines will limit the number)
-		p.writeNewlines(10, '\f')
+		// comment in a different file - separate with newlines
+		p.writeByteN('\f', maxNewlines)
 		return
 	}
 
@@ -270,6 +257,7 @@ func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *as
 	} else {
 		// comment on a different line:
 		// separate with at least one line break
+		droppedLinebreak := false
 		if prev == nil {
 			// first comment of a comment group
 			j := 0
@@ -295,6 +283,7 @@ func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *as
 				case newline, formfeed:
 					// TODO(gri): may want to keep formfeed info in some cases
 					p.wsbuf[i] = ignore
+					droppedLinebreak = true
 				}
 				j = i
 				break
@@ -302,25 +291,41 @@ func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *as
 			p.writeWhitespace(j)
 		}
 
-		// turn off indent if we're about to print a line directive.
-		indent := p.indent
-		if strings.HasPrefix(comment.Text, linePrefix) {
-			p.indent = 0
+		// determine number of linebreaks before the comment
+		n := 0
+		if pos.IsValid() && p.last.IsValid() {
+			n = pos.Line - p.last.Line
+			if n < 0 { // should never happen
+				n = 0
+			}
+		}
+
+		// at the package scope level only (p.indent == 0),
+		// add an extra newline if we dropped one before:
+		// this preserves a blank line before documentation
+		// comments at the package scope level (issue 2570)
+		if p.indent == 0 && droppedLinebreak {
+			n++
 		}
 
-		// use formfeeds to break columns before a comment;
-		// this is analogous to using formfeeds to separate
-		// individual lines of /*-style comments - but make
-		// sure there is at least one line break if the previous
-		// comment was a line comment
-		n := pos.Line - p.last.Line // if !pos.IsValid(), pos.Line == 0, and n will be 0
-		if n <= 0 && prev != nil && prev.Text[1] == '/' {
+		// make sure there is at least one line break
+		// if the previous comment was a line comment
+		if n == 0 && prev != nil && prev.Text[1] == '/' {
 			n = 1
 		}
+
 		if n > 0 {
-			p.writeNewlines(n, '\f')
+			// turn off indent if we're about to print a line directive
+			indent := p.indent
+			if strings.HasPrefix(comment.Text, linePrefix) {
+				p.indent = 0
+			}
+			// use formfeeds to break columns before a comment;
+			// this is analogous to using formfeeds to separate
+			// individual lines of /*-style comments
+			p.writeByteN('\f', nlimit(n))
+			p.indent = indent // restore indent
 		}
-		p.indent = indent
 	}
 }
 
@@ -550,10 +555,11 @@ 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
-// pending whitespace. writeCommentSuffix returns true if a pending
-// formfeed was dropped from the whitespace buffer.
+// pending whitespace. The writeCommentSuffix result indicates if a
+// newline was written or if a formfeed was dropped from the whitespace
+// buffer.
 //
-func (p *printer) writeCommentSuffix(needsLinebreak bool) (droppedFF bool) {
+func (p *printer) writeCommentSuffix(needsLinebreak bool) (wroteNewline, droppedFF bool) {
 	for i, ch := range p.wsbuf {
 		switch ch {
 		case blank, vtab:
@@ -566,6 +572,7 @@ func (p *printer) writeCommentSuffix(needsLinebreak bool) (droppedFF bool) {
 			// but remember if we dropped any formfeeds
 			if needsLinebreak {
 				needsLinebreak = false
+				wroteNewline = true
 			} else {
 				if ch == formfeed {
 					droppedFF = true
@@ -579,6 +586,7 @@ func (p *printer) writeCommentSuffix(needsLinebreak bool) (droppedFF bool) {
 	// make sure we have a line break
 	if needsLinebreak {
 		p.writeByte('\n')
+		wroteNewline = true
 	}
 
 	return
@@ -587,10 +595,10 @@ func (p *printer) writeCommentSuffix(needsLinebreak bool) (droppedFF bool) {
 // intersperseComments consumes all comments that appear before the next token
 // tok 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
-// the comments and whitespace. intersperseComments returns true if a pending
-// formfeed was dropped from the whitespace buffer.
+// the comments and whitespace. The intersperseComments result indicates if a
+// newline was written or if a formfeed was dropped from the whitespace buffer.
 //
-func (p *printer) intersperseComments(next token.Position, tok token.Token) (droppedFF bool) {
+func (p *printer) intersperseComments(next token.Position, tok token.Token) (wroteNewline, droppedFF bool) {
 	var last *ast.Comment
 	for ; p.commentBefore(next); p.cindex++ {
 		for _, c := range p.comments[p.cindex].List {
@@ -618,7 +626,7 @@ func (p *printer) intersperseComments(next token.Position, tok token.Token) (dro
 	// no comment was written - we should never reach here since
 	// intersperseComments should not be called in that case
 	p.internalError("intersperseComments called without pending comments")
-	return false
+	return
 }
 
 // whiteWhitespace writes the first n whitespace entries.
@@ -671,6 +679,14 @@ func (p *printer) writeWhitespace(n int) {
 // ----------------------------------------------------------------------------
 // Printing interface
 
+// nlines limits n to maxNewlines.
+func nlimit(n int) int {
+	if n > maxNewlines {
+		n = maxNewlines
+	}
+	return n
+}
+
 func mayCombine(prev token.Token, next byte) (b bool) {
 	switch prev {
 	case token.INT:
@@ -765,17 +781,22 @@ func (p *printer) print(args ...interface{}) {
 		p.pos = next
 
 		if data != "" {
-			nl := byte('\n')
-			if p.flush(next, tok) {
-				nl = '\f' // dropped formfeed before
-			}
+			wroteNewline, droppedFF := p.flush(next, tok)
 
 			// intersperse extra newlines if present in the source
 			// (don't do this in flush as it will cause extra newlines
-			// at the end of a file) - use formfeeds if we dropped one
-			// before
-			if n := next.Line - p.pos.Line; n > 0 {
-				p.writeNewlines(n, nl)
+			// at the end of a file)
+			n := nlimit(next.Line - p.pos.Line)
+			// don't exceed maxNewlines if we already wrote one
+			if wroteNewline && n == maxNewlines {
+				n = maxNewlines - 1
+			}
+			if n > 0 {
+				ch := byte('\n')
+				if droppedFF {
+					ch = '\f' // use formfeed since we dropped one before
+				}
+				p.writeByteN(ch, n)
 			}
 
 			p.writeItem(next, data, isLit)
@@ -790,16 +811,15 @@ func (p *printer) commentBefore(next token.Position) bool {
 	return p.cindex < len(p.comments) && p.fset.Position(p.comments[p.cindex].List[0].Pos()).Offset < next.Offset
 }
 
-// Flush prints any pending comments and whitespace occurring
-// textually before the position of the next token tok. Flush
-// returns true if a pending formfeed character was dropped
-// from the whitespace buffer as a result of interspersing
-// comments.
+// Flush prints any pending comments and whitespace occurring textually
+// before the position of the next token tok. The Flush result indicates
+// if a newline was written or if a formfeed was dropped from the whitespace
+// buffer.
 //
-func (p *printer) flush(next token.Position, tok token.Token) (droppedFF bool) {
+func (p *printer) flush(next token.Position, tok token.Token) (wroteNewline, droppedFF bool) {
 	if p.commentBefore(next) {
 		// if there are comments before the next item, intersperse them
-		droppedFF = p.intersperseComments(next, tok)
+		wroteNewline, droppedFF = p.intersperseComments(next, tok)
 	} else {
 		// otherwise, write any leftover whitespace
 		p.writeWhitespace(len(p.wsbuf))
@@ -810,7 +830,8 @@ func (p *printer) flush(next token.Position, tok token.Token) (droppedFF bool) {
 // getNode returns the ast.CommentGroup associated with n, if any.
 func getDoc(n ast.Node) *ast.CommentGroup {
 	switch n := n.(type) {
-	// *ast.Fields cannot be printed separately - ignore for now
+	case *ast.Field:
+		return n.Doc
 	case *ast.ImportSpec:
 		return n.Doc
 	case *ast.ValueSpec:
diff --git a/libgo/go/go/printer/testdata/comments.golden b/libgo/go/go/printer/testdata/comments.golden
index 7b332252c4e..d2ad9e3a2ff 100644
--- a/libgo/go/go/printer/testdata/comments.golden
+++ b/libgo/go/go/printer/testdata/comments.golden
@@ -106,7 +106,7 @@ type S3 struct {
 var x int	// x
 var ()
 
-// This comment SHOULD be associated with the next declaration.
+// This comment SHOULD be associated with f0.
 func f0() {
 	const pi = 3.14	// pi
 	var s1 struct{}	/* an empty struct */	/* foo */
@@ -115,8 +115,9 @@ func f0() {
 	var s2 struct{} = struct{}{}
 	x := pi
 }
+
 //
-// NO SPACE HERE
+// This comment should be associated with f1, with one blank line before the comment.
 //
 func f1() {
 	f0()
diff --git a/libgo/go/go/printer/testdata/comments.input b/libgo/go/go/printer/testdata/comments.input
index 2a9a86b6815..222e0a713d4 100644
--- a/libgo/go/go/printer/testdata/comments.input
+++ b/libgo/go/go/printer/testdata/comments.input
@@ -107,7 +107,7 @@ var x int  // x
 var ()
 
 
-// This comment SHOULD be associated with the next declaration.
+// This comment SHOULD be associated with f0.
 func f0() {
 	const pi = 3.14  // pi
 	var s1 struct {}  /* an empty struct */ /* foo */
@@ -117,7 +117,7 @@ func f0() {
 	x := pi
 }
 //
-// NO SPACE HERE
+// This comment should be associated with f1, with one blank line before the comment.
 //
 func f1() {
 	f0()
@@ -130,7 +130,7 @@ func f1() {
 
 
 func _() {
-	// this comment should be properly indented
+// this comment should be properly indented
 }
 
 
diff --git a/libgo/go/go/printer/testdata/declarations.golden b/libgo/go/go/printer/testdata/declarations.golden
index bfa2568c21f..239ba890304 100644
--- a/libgo/go/go/printer/testdata/declarations.golden
+++ b/libgo/go/go/printer/testdata/declarations.golden
@@ -115,6 +115,18 @@ import _ "io"
 
 var _ int
 
+// at least one empty line between declarations of the same kind
+// if there is associated documentation (was issue 2570)
+type T1 struct{}
+
+// T2 comment
+type T2 struct {
+}	// should be a two-line struct
+
+// T3 comment
+type T2 struct {
+}	// should be a two-line struct
+
 // printing of constant literals
 const (
 	_	= "foobar"
@@ -286,6 +298,15 @@ type _ struct {
 	}
 }
 
+// no blank lines in empty structs and interfaces, but leave 1- or 2-line layout alone
+type _ struct{}
+type _ struct {
+}
+
+type _ interface{}
+type _ interface {
+}
+
 // no tabs for single or ungrouped decls
 func _() {
 	const xxxxxx = 0
diff --git a/libgo/go/go/printer/testdata/declarations.input b/libgo/go/go/printer/testdata/declarations.input
index 1d69c57b517..68f90308a36 100644
--- a/libgo/go/go/printer/testdata/declarations.input
+++ b/libgo/go/go/printer/testdata/declarations.input
@@ -115,6 +115,20 @@ import (
 import _ "io"
 var _ int
 
+// at least one empty line between declarations of the same kind
+// if there is associated documentation (was issue 2570)
+type T1 struct{}
+// T2 comment
+type T2 struct {
+} // should be a two-line struct
+
+
+// T3 comment
+type T2 struct {
+
+
+} // should be a two-line struct
+
 
 // printing of constant literals
 const (
@@ -293,6 +307,18 @@ type _ struct {
 }
 
 
+// no blank lines in empty structs and interfaces, but leave 1- or 2-line layout alone
+type _ struct{            }
+type _ struct {
+
+}
+
+type _ interface{            }
+type _ interface {
+
+}
+
+
 // no tabs for single or ungrouped decls
 func _() {
 	const xxxxxx = 0
diff --git a/libgo/go/go/printer/testdata/statements.golden b/libgo/go/go/printer/testdata/statements.golden
index a6d85107f0b..90e1743557d 100644
--- a/libgo/go/go/printer/testdata/statements.golden
+++ b/libgo/go/go/printer/testdata/statements.golden
@@ -271,7 +271,6 @@ func _() {
 	// Known bug: The first use call may have more than one empty line before
 	//            (see go/printer/nodes.go, func linebreak).
 
-
 	use(x)
 
 	if x < x {
@@ -386,7 +385,6 @@ L:	// A comment on the same line as the label, followed by a single empty line.
 	// Known bug: There may be more than one empty line before MoreCode()
 	//            (see go/printer/nodes.go, func linebreak).
 
-
 	MoreCode()
 }