improved spacing around if, switch, and for control clauses

R=r
DELTA=89  (82 added, 5 deleted, 2 changed)
OCL=34870
CL=34870

src/pkg/go/printer/printer.go

@@ -911,30 +911,37 @@ func (p *printer) switchBlock(s *ast.BlockStmt) {
 
 
 func (p *printer) controlClause(isForStmt bool, init ast.Stmt, expr ast.Expr, post ast.Stmt) {
+	p.print(blank);
+	needsBlank := false;
 	if init == nil && post == nil {
 		// no semicolons required
 		if expr != nil {
-			p.print(blank);
 			p.expr(expr);
+			needsBlank = true;
 		}
 	} else {
 		// all semicolons required
 		// (they are not separators, print them explicitly)
-		p.print(blank);
 		if init != nil {
 			p.stmt(init);
 		}
 		p.print(token.SEMICOLON, blank);
 		if expr != nil {
 			p.expr(expr);
+			needsBlank = true;
 		}
 		if isForStmt {
 			p.print(token.SEMICOLON, blank);
+			needsBlank = false;
 			if post != nil {
 				p.stmt(post);
+				needsBlank = true;
 			}
 		}
 	}
+	if needsBlank {
+		p.print(blank);
+	}
 }
 
 
@@ -1007,7 +1014,6 @@ func (p *printer) stmt(stmt ast.Stmt) (optSemi bool) {
 	case *ast.IfStmt:
 		p.print(token.IF);
 		p.controlClause(false, s.Init, s.Cond, nil);
-		p.print(blank);
 		p.block(s.Body);
 		optSemi = true;
 		if s.Else != nil {
@@ -1028,7 +1034,6 @@ func (p *printer) stmt(stmt ast.Stmt) (optSemi bool) {
 	case *ast.SwitchStmt:
 		p.print(token.SWITCH);
 		p.controlClause(false, s.Init, s.Tag, nil);
-		p.print(blank);
 		p.switchBlock(s.Body);
 		optSemi = true;
 
@@ -1077,7 +1082,6 @@ func (p *printer) stmt(stmt ast.Stmt) (optSemi bool) {
 	case *ast.ForStmt:
 		p.print(token.FOR);
 		p.controlClause(true, s.Init, s.Cond, s.Post);
-		p.print(blank);
 		p.block(s.Body);
 		optSemi = true;
 

src/pkg/go/printer/printer_test.go

@@ -103,6 +103,7 @@ var data = []entry{
 	entry{ "linebreaks.go", "linebreaks.golden", false },
 	entry{ "expressions.go", "expressions.golden", false },
 	entry{ "declarations.go", "declarations.golden", false },
+	entry{ "statements.go", "statements.golden", false },
 }
 
 

src/pkg/go/printer/testdata/statements.go

@@ -0,0 +1,37 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package statements
+
+var expr bool;
+
+func _() {
+	if {}
+	if expr{}
+	if _:=expr;{}
+	if _:=expr; expr {}
+}
+
+
+func _() {
+	switch {}
+	switch expr {}
+	switch _ := expr; {}
+	switch _ := expr; expr {}
+}
+
+
+func _() {
+	for{}
+	for expr {}
+	for;;{}  // TODO ok to lose the semicolons here?
+	for _ :=expr;; {}
+	for; expr;{}  // TODO ok to lose the semicolons here?
+	for; ; expr = false {}
+	for _ :=expr; expr; {}
+	for _ := expr;; expr=false {}
+	for;expr;expr =false {}
+	for _ := expr;expr;expr = false {}
+	for _ := range []int{} {}
+}

src/pkg/go/printer/testdata/statements.golden

@@ -0,0 +1,35 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package statements
+
+var expr bool
+
+func _() {
+	if {}
+	if expr {}
+	if _ := expr; {}
+	if _ := expr; expr {}
+}
+
+func _() {
+	switch {}
+	switch expr {}
+	switch _ := expr; {}
+	switch _ := expr; expr {}
+}
+
+func _() {
+	for {}
+	for expr {}
+	for {}	// TODO ok to lose the semicolons here?
+	for _ := expr; ; {}
+	for expr {}	// TODO ok to lose the semicolons here?
+	for ; ; expr = false {}
+	for _ := expr; expr; {}
+	for _ := expr; ; expr = false {}
+	for ; expr; expr = false {}
+	for _ := expr; expr; expr = false {}
+	for _ := range []int{} {}
+}