[modules] Infer strict mode from within scope object

Refactor the Scope object to automatically enable strict mode when
initialized as a "module" scope, relieving the caller of this
responsibility.

BUG=v8:4941
LOG=N
R=adamk@chromium.org

Review URL: https://codereview.chromium.org/1906923002

Cr-Commit-Position: refs/heads/master@{#35730}

src/ast/scopes.cc

@@ -175,7 +175,10 @@ void Scope::SetDefaults(ScopeType scope_type, Scope* outer_scope,
   asm_module_ = false;
   asm_function_ = outer_scope != NULL && outer_scope->asm_module_;
   // Inherit the language mode from the parent scope.
-  language_mode_ = outer_scope != NULL ? outer_scope->language_mode_ : SLOPPY;
+  language_mode_ =
+      is_module_scope()
+          ? STRICT
+          : (outer_scope != NULL ? outer_scope->language_mode_ : SLOPPY);
   outer_scope_calls_sloppy_eval_ = false;
   inner_scope_calls_eval_ = false;
   scope_nonlinear_ = false;

src/ast/scopes.h

@@ -243,6 +243,7 @@ class Scope: public ZoneObject {
 
   // Set the language mode flag (unless disabled by a global flag).
   void SetLanguageMode(LanguageMode language_mode) {
+    DCHECK(!is_module_scope());
     language_mode_ = language_mode;
   }
 

src/parsing/parser.cc

@@ -917,15 +917,15 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
     FunctionState function_state(&function_state_, &scope_, scope,
                                  kNormalFunction, &function_factory);
 
-    // Don't count the mode in the use counters--give the program a chance
-    // to enable script/module-wide strict mode below.
-    scope_->SetLanguageMode(info->language_mode());
     ZoneList<Statement*>* body = new(zone()) ZoneList<Statement*>(16, zone());
     bool ok = true;
     int beg_pos = scanner()->location().beg_pos;
     if (info->is_module()) {
       ParseModuleItemList(body, &ok);
     } else {
+      // Don't count the mode in the use counters--give the program a chance
+      // to enable script-wide strict mode below.
+      scope_->SetLanguageMode(info->language_mode());
       ParseStatementList(body, Token::EOS, &ok);
     }
 
@@ -1295,7 +1295,6 @@ void* Parser::ParseModuleItemList(ZoneList<Statement*>* body, bool* ok) {
   //    ModuleItem*
 
   DCHECK(scope_->is_module_scope());
-  RaiseLanguageMode(STRICT);
 
   while (peek() != Token::EOS) {
     Statement* stat = ParseModuleItem(CHECK_OK);

src/parsing/preparser.h

@@ -969,8 +969,9 @@ class PreParser : public ParserBase<PreParserTraits> {
   // success (even if parsing failed, the pre-parse data successfully
   // captured the syntax error), and false if a stack-overflow happened
   // during parsing.
-  PreParseResult PreParseProgram(int* materialized_literals = 0) {
-    Scope* scope = NewScope(scope_, SCRIPT_SCOPE);
+  PreParseResult PreParseProgram(int* materialized_literals = 0,
+                                 bool is_module = false) {
+    Scope* scope = NewScope(scope_, is_module ? MODULE_SCOPE : SCRIPT_SCOPE);
     PreParserFactory factory(NULL);
     FunctionState top_scope(&function_state_, &scope_, scope, kNormalFunction,
                             &factory);

test/cctest/test-parsing.cc

@@ -1555,8 +1555,8 @@ void TestParserSyncWithFlags(i::Handle<i::String> source,
                            stack_limit);
     SetParserFlags(&preparser, flags);
     scanner.Initialize(&stream);
-    i::PreParser::PreParseResult result = preparser.PreParseProgram(
-        &preparser_materialized_literals);
+    i::PreParser::PreParseResult result =
+        preparser.PreParseProgram(&preparser_materialized_literals, is_module);
     CHECK_EQ(i::PreParser::kPreParseSuccess, result);
   }
   bool preparse_error = log.HasError();