Introduce ModuleScope subclass of DeclarationScope

This moves the module_descriptor_ field to that subclass, as well as other module-only methods.

BUG=v8:5209

Review-Url: https://codereview.chromium.org/2252223002
Cr-Commit-Position: refs/heads/master@{#38703}

src/ast/modules.cc

@@ -97,10 +97,9 @@ void ModuleDescriptor::MakeIndirectExportsExplicit() {
   }
 }
 
-bool ModuleDescriptor::Validate(DeclarationScope* module_scope,
+bool ModuleDescriptor::Validate(ModuleScope* module_scope,
                                 PendingCompilationErrorHandler* error_handler,
                                 Zone* zone) {
-  DCHECK(module_scope->is_module_scope());
   DCHECK_EQ(this, module_scope->module());
   DCHECK_NOT_NULL(error_handler);
 

src/ast/modules.h

@@ -64,7 +64,7 @@ class ModuleDescriptor : public ZoneObject {
 
   // Check if module is well-formed and report error if not.
   // Also canonicalize indirect exports.
-  bool Validate(DeclarationScope* module_scope,
+  bool Validate(ModuleScope* module_scope,
                 PendingCompilationErrorHandler* error_handler, Zone* zone);
 
   struct ModuleEntry : public ZoneObject {

src/ast/scopes.cc

@@ -111,10 +111,14 @@ DeclarationScope::DeclarationScope(Zone* zone, Scope* outer_scope,
       params_(4, zone),
       sloppy_block_function_map_(zone) {
   SetDefaults();
-  if (scope_type == MODULE_SCOPE) {
-    module_descriptor_ = new (zone) ModuleDescriptor(zone);
-    language_mode_ = STRICT;
-  }
+}
+
+ModuleScope::ModuleScope(Zone* zone, DeclarationScope* script_scope,
+                         AstValueFactory* ast_value_factory)
+    : DeclarationScope(zone, script_scope, MODULE_SCOPE) {
+  module_descriptor_ = new (zone) ModuleDescriptor(zone);
+  set_language_mode(STRICT);
+  DeclareThis(ast_value_factory);
 }
 
 Scope::Scope(Zone* zone, Scope* inner_scope, ScopeType scope_type,
@@ -181,7 +185,6 @@ void DeclarationScope::SetDefaults() {
   arity_ = 0;
   rest_parameter_ = nullptr;
   rest_index_ = -1;
-  module_descriptor_ = nullptr;
 }
 
 void Scope::SetDefaults() {
@@ -366,6 +369,16 @@ const DeclarationScope* Scope::AsDeclarationScope() const {
   return static_cast<const DeclarationScope*>(this);
 }
 
+ModuleScope* Scope::AsModuleScope() {
+  DCHECK(is_module_scope());
+  return static_cast<ModuleScope*>(this);
+}
+
+const ModuleScope* Scope::AsModuleScope() const {
+  DCHECK(is_module_scope());
+  return static_cast<const ModuleScope*>(this);
+}
+
 int Scope::num_parameters() const {
   return is_declaration_scope() ? AsDeclarationScope()->num_parameters() : 0;
 }
@@ -1690,7 +1703,7 @@ void DeclarationScope::AllocateLocals() {
   }
 }
 
-void DeclarationScope::AllocateModuleVariables() {
+void ModuleScope::AllocateModuleVariables() {
   for (auto it = module()->regular_imports().begin();
        it != module()->regular_imports().end(); ++it) {
     Variable* var = LookupLocal(it->second->local_name);
@@ -1721,7 +1734,7 @@ void Scope::AllocateVariablesRecursively() {
   // Parameters must be allocated first, if any.
   if (is_declaration_scope()) {
     if (is_module_scope()) {
-      AsDeclarationScope()->AllocateModuleVariables();
+      AsModuleScope()->AllocateModuleVariables();
     } else if (is_function_scope()) {
       AsDeclarationScope()->AllocateParameterLocals();
     }

src/ast/scopes.h

@@ -69,13 +69,10 @@ class SloppyBlockFunctionMap : public ZoneHashMap {
 // a location. Note that many VariableProxy nodes may refer to the same Java-
 // Script variable.
 
-class DeclarationScope;
-
-// JS environments are represented in the parser using two scope classes, Scope
-// and its subclass DeclarationScope. DeclarationScope is used for any scope
-// that hosts 'var' declarations. This includes script, module, eval, varblock,
-// and function scope. All fields required by such scopes are only available on
-// DeclarationScope.
+// JS environments are represented in the parser using Scope, DeclarationScope
+// and ModuleScope. DeclarationScope is used for any scope that hosts 'var'
+// declarations. This includes script, module, eval, varblock, and function
+// scope. ModuleScope further specializes DeclarationScope.
 class Scope: public ZoneObject {
  public:
   // ---------------------------------------------------------------------------
@@ -95,6 +92,8 @@ class Scope: public ZoneObject {
 
   DeclarationScope* AsDeclarationScope();
   const DeclarationScope* AsDeclarationScope() const;
+  ModuleScope* AsModuleScope();
+  const ModuleScope* AsModuleScope() const;
 
   class Snapshot final BASE_EMBEDDED {
    public:
@@ -444,6 +443,11 @@ class Scope: public ZoneObject {
   bool HasSimpleParameters();
   void set_is_debug_evaluate_scope() { is_debug_evaluate_scope_ = true; }
 
+ protected:
+  void set_language_mode(LanguageMode language_mode) {
+    language_mode_ = language_mode;
+  }
+
  private:
   Zone* zone_;
 
@@ -673,14 +677,6 @@ class DeclarationScope : public Scope {
              IsClassConstructor(function_kind())));
   }
 
-  // The ModuleDescriptor for this scope; only for module scopes.
-  // TODO(verwaest): Move to ModuleScope?
-  ModuleDescriptor* module() const {
-    DCHECK(is_module_scope());
-    DCHECK_NOT_NULL(module_descriptor_);
-    return module_descriptor_;
-  }
-
   void DeclareThis(AstValueFactory* ast_value_factory);
   void DeclareDefaultFunctionVariables(AstValueFactory* ast_value_factory);
 
@@ -847,9 +843,6 @@ class DeclarationScope : public Scope {
   void AllocateLocals();
   void AllocateParameterLocals();
   void AllocateReceiver();
-  // Set MODULE as VariableLocation for all variables that will live in some
-  // module's export table.
-  void AllocateModuleVariables();
 
  private:
   void AllocateParameter(Variable* var, int index);
@@ -881,7 +874,23 @@ class DeclarationScope : public Scope {
   Variable* arguments_;
   // Convenience variable; Subclass constructor only
   Variable* this_function_;
-  // Module descriptor; module scopes only.
+};
+
+class ModuleScope final : public DeclarationScope {
+ public:
+  ModuleScope(Zone* zone, DeclarationScope* script_scope,
+              AstValueFactory* ast_value_factory);
+
+  ModuleDescriptor* module() const {
+    DCHECK_NOT_NULL(module_descriptor_);
+    return module_descriptor_;
+  }
+
+  // Set MODULE as VariableLocation for all variables that will live in some
+  // module's export table.
+  void AllocateModuleVariables();
+
+ private:
   ModuleDescriptor* module_descriptor_;
 };
 

src/globals.h

@@ -430,6 +430,7 @@ class ParameterCount;
 class Foreign;
 class Scope;
 class DeclarationScope;
+class ModuleScope;
 class ScopeInfo;
 class Script;
 class Smi;

src/parsing/parser-base.h

@@ -618,12 +618,8 @@ class ParserBase : public Traits {
     return new (zone()) DeclarationScope(zone(), scope(), BLOCK_SCOPE);
   }
 
-  DeclarationScope* NewModuleScope(Scope* parent) {
-    DeclarationScope* result =
-        new (zone()) DeclarationScope(zone(), parent, MODULE_SCOPE);
-    // TODO(verwaest): Move into the DeclarationScope constructor.
-    result->DeclareThis(ast_value_factory());
-    return result;
+  ModuleScope* NewModuleScope(DeclarationScope* parent) {
+    return new (zone()) ModuleScope(zone(), parent, ast_value_factory());
   }
 
   DeclarationScope* NewEvalScope(Scope* parent) {
@@ -1234,7 +1230,7 @@ class ParserBase : public Traits {
   };
 
   ModuleDescriptor* module() const {
-    return scope()->AsDeclarationScope()->module();
+    return scope()->AsModuleScope()->module();
   }
   Scope* scope() const { return scope_state_->scope(); }
 

src/parsing/parser.cc

@@ -1004,7 +1004,8 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
       }
       outer = NewEvalScope(outer);
     } else if (info->is_module()) {
-      outer = NewModuleScope(outer);
+      DCHECK_EQ(outer, info->script_scope());
+      outer = NewModuleScope(info->script_scope());
     }
 
     DeclarationScope* scope = outer->AsDeclarationScope();
@@ -1023,7 +1024,7 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
     if (parsing_module_) {
       ParseModuleItemList(body, &ok);
       ok = ok &&
-           module()->Validate(this->scope()->AsDeclarationScope(),
+           module()->Validate(this->scope()->AsModuleScope(),
                               &pending_error_handler_, zone());
     } else {
       // Don't count the mode in the use counters--give the program a chance

src/parsing/preparser.h

@@ -1036,7 +1036,7 @@ class PreParser : public ParserBase<PreParserTraits> {
   PreParseResult PreParseProgram(int* materialized_literals = 0,
                                  bool is_module = false) {
     DCHECK_NULL(scope_state_);
-    Scope* scope = NewScriptScope();
+    DeclarationScope* scope = NewScriptScope();
 
     // ModuleDeclarationInstantiation for Source Text Module Records creates a
     // new Module Environment Record whose outer lexical environment record is

test/cctest/test-parsing.cc

@@ -5982,7 +5982,7 @@ TEST(ModuleParsingInternals) {
   CHECK(parser.Parse(&info));
   CHECK(i::Compiler::Analyze(&info));
   i::FunctionLiteral* func = info.literal();
-  i::DeclarationScope* module_scope = func->scope();
+  i::ModuleScope* module_scope = func->scope()->AsModuleScope();
   i::Scope* outer_scope = module_scope->outer_scope();
   CHECK(outer_scope->is_script_scope());
   CHECK_NULL(outer_scope->outer_scope());