Fixed preparser for try statement. Tiny cleanup.

BUG=v8:2109
TBR=jkummerow@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10270007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11468 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/preparser.cc

@@ -581,9 +581,8 @@ PreParser::Statement PreParser::ParseWithStatement(bool* ok) {
   ParseExpression(true, CHECK_OK);
   Expect(i::Token::RPAREN, CHECK_OK);
 
-  scope_->EnterWith();
+  Scope::InsideWith iw(scope_);
   ParseStatement(CHECK_OK);
-  scope_->LeaveWith();
   return Statement::Default();
 }
 
@@ -749,10 +748,9 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
       return Statement::Default();
     }
     Expect(i::Token::RPAREN, CHECK_OK);
-    scope_->EnterWith();
-    ParseBlock(ok);
-    scope_->LeaveWith();
-    if (!*ok) Statement::Default();
+    { Scope::InsideWith iw(scope_);
+      ParseBlock(CHECK_OK);
+    }
     catch_or_finally_seen = true;
   }
   if (peek() == i::Token::FINALLY) {

src/preparser.h

@@ -470,8 +470,19 @@ class PreParser {
     void set_language_mode(i::LanguageMode language_mode) {
       language_mode_ = language_mode;
     }
-    void EnterWith() { with_nesting_count_++; }
-    void LeaveWith() { with_nesting_count_--; }
+
+    class InsideWith {
+     public:
+      explicit InsideWith(Scope* scope) : scope_(scope) {
+        scope->with_nesting_count_++;
+      }
+
+      ~InsideWith() { scope_->with_nesting_count_--; }
+
+     private:
+      Scope* scope_;
+      DISALLOW_COPY_AND_ASSIGN(InsideWith);
+    };
 
    private:
     Scope** const variable_;