Add strong mode.

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 0dbfe5d18522d4799207318a42f22f879fd08f35..ecc14782792147f1545eb61774680165d6394f46 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -289,7 +289,7 @@ FunctionLiteral* Parser::DefaultConstructor(bool call_super, Scope* scope,
   Scope* function_scope =
       NewScope(scope, FUNCTION_SCOPE, FunctionKind::kDefaultConstructor);
   function_scope->SetLanguageMode(
-      static_cast<LanguageMode>(scope->language_mode() | STRICT));
+      static_cast<LanguageMode>(scope->language_mode() | STRICT_BIT));
   // Set start and end position to the same value
   function_scope->set_start_position(pos);
   function_scope->set_end_position(pos);
@@ -1145,13 +1145,23 @@ void* Parser::ParseStatementList(ZoneList<Statement*>* body, int end_token,
       if ((e_stat = stat->AsExpressionStatement()) != NULL &&
           (literal = e_stat->expression()->AsLiteral()) != NULL &&
           literal->raw_value()->IsString()) {
-        // Check "use strict" directive (ES5 14.1) and "use asm" directive. Only
-        // one can be present.
-        if (is_sloppy(language_mode()) &&
+        // Check "use strict" directive (ES5 14.1), "use asm" directive, and
+        // "use sanity" directive (experimental). Only one can be present.
+        bool use_strict_found =
+            is_sloppy(language_mode()) &&
             literal->raw_value()->AsString() ==
                 ast_value_factory()->use_strict_string() &&
             token_loc.end_pos - token_loc.beg_pos ==
-                ast_value_factory()->use_strict_string()->length() + 2) {
+                ast_value_factory()->use_strict_string()->length() + 2;
+        bool use_sanity_found =

[arv (Not doing code reviews), 2015/02/04 16:17:11]

Don't we want a flag for this work?

[rossberg, 2015/02/04 16:19:57]

Ah, excellent point! Yes, we need a flag. I suggest --sane-mode.

[marja, 2015/02/05 12:11:37]

Done.

+            !use_strict_found && !is_sane(language_mode()) &&

[rossberg, 2015/02/04 16:18:09]

If I read this correctly then

  "use sanity"; "use strict";

will turn on sane mode, while

  "use strict"; "use sanity";

will leave you in strict mode. That would be weird. I think it should be fine to
redundantly have both directives in either order.

[marja, 2015/02/05 12:11:37]

Done. (Oops, preparser was already following that logic.)

+            literal->raw_value()->AsString() ==
+                ast_value_factory()->use_sanity_string() &&
+            token_loc.end_pos - token_loc.beg_pos ==
+                ast_value_factory()->use_sanity_string()->length() + 2;
+        if (use_strict_found || use_sanity_found) {
+          // Sane mode implies strict mode.
+
           // TODO(mstarzinger): Global strict eval calls, need their own scope
           // as specified in ES5 10.4.2(3). The correct fix would be to always
           // add this scope in DoParseProgram(), but that requires adaptations
@@ -1170,8 +1180,14 @@ void* Parser::ParseStatementList(ZoneList<Statement*>* body, int end_token,
             mode_ = PARSE_EAGERLY;
           }
           scope_->SetLanguageMode(
-              static_cast<LanguageMode>(scope_->language_mode() | STRICT));
-          // "use strict" is the only directive for now.
+              static_cast<LanguageMode>(scope_->language_mode() | STRICT_BIT));
+
+          if (use_sanity_found) {
+            scope_->SetLanguageMode(
+                static_cast<LanguageMode>(scope_->language_mode() | SANE_BIT));
+          }
+
+          // Don't allow additional directives.
           directive_prologue = false;
         } else if (literal->raw_value()->AsString() ==
                        ast_value_factory()->use_asm_string() &&
@@ -1181,6 +1197,8 @@ void* Parser::ParseStatementList(ZoneList<Statement*>* body, int end_token,
           // incremented after parsing is done.
           ++use_counts_[v8::Isolate::kUseAsm];
           scope_->SetAsmModule();
+          // Don't allow additional directives.
+          directive_prologue = false;
         }
       } else {
         // End of the directive prologue.
@@ -1257,7 +1275,7 @@ Module* Parser::ParseModule(bool* ok) {
 
   scope->set_start_position(scanner()->location().beg_pos);
   scope->SetLanguageMode(
-      static_cast<LanguageMode>(scope->language_mode() | STRICT));
+      static_cast<LanguageMode>(scope->language_mode() | STRICT_BIT));
 
   {
     BlockState block_state(&scope_, scope);
@@ -4036,7 +4054,7 @@ ClassLiteral* Parser::ParseClassLiteral(const AstRawString* name,
   Scope* block_scope = NewScope(scope_, BLOCK_SCOPE);
   BlockState block_state(&scope_, block_scope);
   scope_->SetLanguageMode(
-      static_cast<LanguageMode>(scope_->language_mode() | STRICT));
+      static_cast<LanguageMode>(scope_->language_mode() | STRICT_BIT));
   scope_->SetScopeName(name);
 
   VariableProxy* proxy = NULL;