From 8e7873672e7d5b1f727fbc5d56ba4dea322d54f7 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Thu, 12 Feb 2009 16:06:21 -0800
Subject: [PATCH] - fixed bugs related to the empty statement   (now in sync
 with the spec and with 6g) - fixed incorrect logging statement in gds

R=r
OCL=24970
CL=24970
---
 usr/gri/pretty/ast.go     |  6 ++++++
 usr/gri/pretty/gds.go     |  2 +-
 usr/gri/pretty/parser.go  | 33 +++++++++++++++------------------
 usr/gri/pretty/printer.go |  6 ++++++
 4 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/usr/gri/pretty/ast.go b/usr/gri/pretty/ast.go
index b3260a1fa4..df8bfbf2cd 100644
--- a/usr/gri/pretty/ast.go
+++ b/usr/gri/pretty/ast.go
@@ -390,6 +390,10 @@ type (
 		Tok int;  // BREAK, CONTINUE, GOTO, FALLTHROUGH
 		Label *Ident;  // if any, or nil
 	};
+	
+	EmptyStat struct {
+		Pos int;  // position of ";"
+	};
 )
 
 
@@ -405,6 +409,7 @@ type StatVisitor interface {
 	DoSwitchStat(s *SwitchStat);
 	DoSelectStat(s *SelectStat);
 	DoControlFlowStat(s *ControlFlowStat);
+	DoEmptyStat(s *EmptyStat);
 }
 
 
@@ -419,6 +424,7 @@ func (s *CaseClause) Visit(v StatVisitor) { v.DoCaseClause(s); }
 func (s *SwitchStat) Visit(v StatVisitor) { v.DoSwitchStat(s); }
 func (s *SelectStat) Visit(v StatVisitor) { v.DoSelectStat(s); }
 func (s *ControlFlowStat) Visit(v StatVisitor) { v.DoControlFlowStat(s); }
+func (s *EmptyStat) Visit(v StatVisitor) { v.DoEmptyStat(s); }
 
 
 // ----------------------------------------------------------------------------
diff --git a/usr/gri/pretty/gds.go b/usr/gri/pretty/gds.go
index d5637cc9df..284a9d5073 100644
--- a/usr/gri/pretty/gds.go
+++ b/usr/gri/pretty/gds.go
@@ -155,7 +155,7 @@ func main() {
 	http.Handle("/", http.HandlerFunc(serve));
 	err2 := http.ListenAndServe(":" + *port, nil);
 	if err2 != nil {
-		log.Exitf("ListenAndServe: ", err2.String())
+		log.Exitf("ListenAndServe: %s", err2.String())
 	}
 }
 
diff --git a/usr/gri/pretty/parser.go b/usr/gri/pretty/parser.go
index b5cbcd72bf..5543d9eeb3 100644
--- a/usr/gri/pretty/parser.go
+++ b/usr/gri/pretty/parser.go
@@ -733,25 +733,21 @@ func (P *Parser) parseStatementList(list *array.Array) {
 		defer un(trace(P, "StatementList"));
 	}
 
+	expect_semi := false;
 	for P.tok != Scanner.CASE && P.tok != Scanner.DEFAULT && P.tok != Scanner.RBRACE && P.tok != Scanner.EOF {
-		s := P.parseStatement();
-		if s != nil {
-			// not the empty statement
-			list.Push(s);
+		if expect_semi {
+			P.expect(Scanner.SEMICOLON);
+			expect_semi = false;
 		}
+		list.Push(P.parseStatement());
 		if P.tok == Scanner.SEMICOLON {
 			P.next();
 		} else if P.opt_semi {
 			P.opt_semi = false;  // "consume" optional semicolon
 		} else {
-			break;
+			expect_semi = true;
 		}
 	}
-
-	// Try to provide a good error message
-	if P.tok != Scanner.CASE && P.tok != Scanner.DEFAULT && P.tok != Scanner.RBRACE && P.tok != Scanner.EOF {
-		P.error(P.pos, "expected end of statement list (semicolon missing?)");
-	}
 }
 
 
@@ -1273,12 +1269,9 @@ func (P *Parser) parseIfStat() *AST.IfStat {
 	var else_ AST.Stat;
 	if P.tok == Scanner.ELSE {
 		P.next();
-		if P.tok == Scanner.IF || P.tok == Scanner.LBRACE {
+		if ok := P.tok == Scanner.IF || P.tok == Scanner.LBRACE; ok || P.sixg {
 			else_ = P.parseStatement();
-		} else if P.sixg {
-			else_ = P.parseStatement();
-			if else_ != nil {
-				// not the empty statement
+			if !ok {
 				// wrap in a block since we don't have one
 				body := AST.NewBlock(0, Scanner.LBRACE);
 				body.List.Push(else_);
@@ -1290,7 +1283,7 @@ func (P *Parser) parseIfStat() *AST.IfStat {
 	}
 	P.closeScope();
 
-	return &AST.IfStat{pos, init, cond, body, else_ };
+	return &AST.IfStat{pos, init, cond, body, else_};
 }
 
 
@@ -1438,10 +1431,14 @@ func (P *Parser) parseStatement() AST.Stat {
 		return P.parseSwitchStat();
 	case Scanner.SELECT:
 		return P.parseSelectStat();
+	case Scanner.SEMICOLON:
+		// don't consume the ";", it is the separator following the empty statement
+		return &AST.EmptyStat{P.pos};
 	}
 
-	// empty statement
-	return nil;
+	// no statement found
+	P.error(P.pos, "statement expected");
+	return &AST.BadStat{P.pos};
 }
 
 
diff --git a/usr/gri/pretty/printer.go b/usr/gri/pretty/printer.go
index d29bfd1ee6..a0de7d06a6 100644
--- a/usr/gri/pretty/printer.go
+++ b/usr/gri/pretty/printer.go
@@ -919,6 +919,12 @@ func (P *Printer) DoControlFlowStat(s *AST.ControlFlowStat) {
 }
 
 
+func (P *Printer) DoEmptyStat(s *AST.EmptyStat) {
+	P.String(s.Pos, "");
+	P.separator = semicolon;
+}
+
+
 // ----------------------------------------------------------------------------
 // Declarations
 
-- 
2.48.1