Separate Scope into DeclarationScope and Scope

src/ast/scopes.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/ast/scopes.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parsing/parser.h"  // for ParseInfo
@@ skipping 63 matching lines @@
     p->value = new (zone_->New(sizeof(Vector))) Vector(zone_);
   }
   Vector* delegates = static_cast<Vector*>(p->value);
   delegates->push_back(stmt);
 }
 
 
 // ----------------------------------------------------------------------------
 // Implementation of Scope
 
-Scope::Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type,
-             FunctionKind function_kind)
+Scope::Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type)
     : outer_scope_(outer_scope),
       variables_(zone),
-      temps_(4, zone),
-      params_(4, zone),
       decls_(4, zone),
-      module_descriptor_(scope_type == MODULE_SCOPE ? new (zone)
-                                                          ModuleDescriptor(zone)
-                                                    : NULL),
-      sloppy_block_function_map_(zone),
       scope_type_(scope_type),
-      function_kind_(function_kind),
       already_resolved_(false) {
   SetDefaults();
   if (outer_scope == nullptr) {
     // If the outer scope is null, this cannot be a with scope. The outermost
     // scope must be a script scope.
     DCHECK_EQ(SCRIPT_SCOPE, scope_type);
   } else {
     asm_function_ = outer_scope_->asm_module_;
     // Inherit the language mode from the parent scope unless we're a module
     // scope.
     if (!is_module_scope()) language_mode_ = outer_scope->language_mode_;
     force_context_allocation_ =
         !is_function_scope() && outer_scope->has_forced_context_allocation();
     outer_scope_->AddInnerScope(this);
     scope_inside_with_ = outer_scope_->scope_inside_with_ || is_with_scope();
   }
 }
 
+Scope::Snapshot::Snapshot(Scope* scope)
+    : outer_scope_(scope),
+      top_inner_scope_(scope->inner_scope_),
+      top_unresolved_(scope->unresolved_),
+      top_temp_(scope->GetClosureScope()->temps()->length()) {}
+
+DeclarationScope::DeclarationScope(Zone* zone, Scope* outer_scope,
+                                   ScopeType scope_type,
+                                   FunctionKind function_kind)
+    : Scope(zone, outer_scope, scope_type),
+      function_kind_(function_kind),
+      temps_(4, zone),
+      params_(4, zone),
+      sloppy_block_function_map_(zone),
+      module_descriptor_(scope_type == MODULE_SCOPE ? new (zone)
+                                                          ModuleDescriptor(zone)
+                                                    : NULL) {
+  SetDefaults();
+}
+
 Scope::Scope(Zone* zone, Scope* inner_scope, ScopeType scope_type,
              Handle<ScopeInfo> scope_info)
     : outer_scope_(nullptr),
       variables_(zone),
-      temps_(4, zone),
-      params_(4, zone),
       decls_(4, zone),
-      module_descriptor_(nullptr),
-      sloppy_block_function_map_(zone),
       scope_type_(scope_type),
-      function_kind_(scope_info.is_null() ? kNormalFunction
-                                          : scope_info->function_kind()),
       already_resolved_(true),
       scope_info_(scope_info) {
   SetDefaults();
   if (!scope_info.is_null()) {
     scope_calls_eval_ = scope_info->CallsEval();
     language_mode_ = scope_info->language_mode();
-    is_declaration_scope_ = scope_info->is_declaration_scope();
     num_heap_slots_ = scope_info_->ContextLength();
   }
   // Ensure at least MIN_CONTEXT_SLOTS to indicate a materialized context.
   num_heap_slots_ = Max(num_heap_slots_,
                         static_cast<int>(Context::MIN_CONTEXT_SLOTS));
   AddInnerScope(inner_scope);
 }
 
+DeclarationScope::DeclarationScope(Zone* zone, Scope* inner_scope,
+                                   ScopeType scope_type,
+                                   Handle<ScopeInfo> scope_info)
+    : Scope(zone, inner_scope, scope_type, scope_info),
+      function_kind_(scope_info.is_null() ? kNormalFunction
+                                          : scope_info->function_kind()),
+      temps_(4, zone),
+      params_(4, zone),
+      sloppy_block_function_map_(zone),
+      module_descriptor_(nullptr) {
+  SetDefaults();
+}
+
 Scope::Scope(Zone* zone, Scope* inner_scope,
              const AstRawString* catch_variable_name)
     : outer_scope_(nullptr),
       variables_(zone),
-      temps_(0, zone),
-      params_(0, zone),
       decls_(0, zone),
-      module_descriptor_(nullptr),
-      sloppy_block_function_map_(zone),
       scope_type_(CATCH_SCOPE),
-      function_kind_(kNormalFunction),
       already_resolved_(true) {
   SetDefaults();
   AddInnerScope(inner_scope);
   num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;
   Variable* variable = variables_.Declare(this,
                                           catch_variable_name,
                                           VAR,
                                           Variable::NORMAL,
                                           kCreatedInitialized);
   AllocateHeapSlot(variable);
 }
 
-void Scope::SetDefaults() {
-  is_declaration_scope_ =
-      is_eval_scope() || is_function_scope() ||
-      is_module_scope() || is_script_scope();
-  inner_scope_ = nullptr;
-  sibling_ = nullptr;
-  unresolved_ = nullptr;
-#ifdef DEBUG
-  scope_name_ = nullptr;
-#endif
-  dynamics_ = nullptr;
+void DeclarationScope::SetDefaults() {
+  is_declaration_scope_ = true;
   receiver_ = nullptr;
   new_target_ = nullptr;
   function_ = nullptr;
   arguments_ = nullptr;
   this_function_ = nullptr;
+  arity_ = 0;
+  has_simple_parameters_ = true;
+  rest_parameter_ = NULL;
+  rest_index_ = -1;
+}
+
+void Scope::SetDefaults() {
+#ifdef DEBUG
+  scope_name_ = nullptr;
+#endif
+  is_declaration_scope_ = false;
+  inner_scope_ = nullptr;
+  sibling_ = nullptr;
+  unresolved_ = nullptr;
+  dynamics_ = nullptr;
   scope_inside_with_ = false;
   scope_calls_eval_ = false;
   has_arguments_parameter_ = false;
   scope_uses_super_property_ = false;
   asm_module_ = false;
   asm_function_ = false;
   language_mode_ = is_module_scope() ? STRICT : SLOPPY;
   outer_scope_calls_sloppy_eval_ = false;
   inner_scope_calls_eval_ = false;
   scope_nonlinear_ = false;
   force_eager_compilation_ = false;
   force_context_allocation_ = false;
   num_stack_slots_ = 0;
   num_heap_slots_ = 0;
   num_global_slots_ = 0;
-  arity_ = 0;
-  has_simple_parameters_ = true;
-  rest_parameter_ = NULL;
-  rest_index_ = -1;
   start_position_ = kNoSourcePosition;
   end_position_ = kNoSourcePosition;
   is_hidden_ = false;
 }
 
+bool Scope::HasSimpleParameters() {
+  DeclarationScope* scope = GetClosureScope();
+  return !scope->is_function_scope() || scope->has_simple_parameters();
+}
+
 Scope* Scope::DeserializeScopeChain(Isolate* isolate, Zone* zone,
                                     Context* context, Scope* script_scope,
                                     AstValueFactory* ast_value_factory) {
   // Reconstruct the outer scope chain from a closure's context chain.
   Scope* current_scope = NULL;
   Scope* innermost_scope = NULL;
   while (!context->IsNativeContext()) {
     if (context->IsWithContext() || context->IsDebugEvaluateContext()) {
       // For scope analysis, debug-evaluate is equivalent to a with scope.
       Scope* with_scope = new (zone)
           Scope(zone, current_scope, WITH_SCOPE, Handle<ScopeInfo>::null());
       current_scope = with_scope;
       // All the inner scopes are inside a with.
       for (Scope* s = innermost_scope; s != NULL; s = s->outer_scope()) {
         s->scope_inside_with_ = true;
       }
     } else if (context->IsScriptContext()) {
       ScopeInfo* scope_info = context->scope_info();
-      current_scope = new (zone) Scope(zone, current_scope, SCRIPT_SCOPE,
-                                       Handle<ScopeInfo>(scope_info));
+      current_scope = new (zone) DeclarationScope(
+          zone, current_scope, SCRIPT_SCOPE, Handle<ScopeInfo>(scope_info));
     } else if (context->IsFunctionContext()) {
       ScopeInfo* scope_info = context->closure()->shared()->scope_info();
-      current_scope = new (zone) Scope(zone, current_scope, FUNCTION_SCOPE,
-                                       Handle<ScopeInfo>(scope_info));
+      current_scope = new (zone) DeclarationScope(
+          zone, current_scope, FUNCTION_SCOPE, Handle<ScopeInfo>(scope_info));
       if (scope_info->IsAsmFunction()) current_scope->asm_function_ = true;
       if (scope_info->IsAsmModule()) current_scope->asm_module_ = true;
     } else if (context->IsBlockContext()) {
       ScopeInfo* scope_info = context->scope_info();
-      current_scope = new (zone) Scope(zone, current_scope, BLOCK_SCOPE,
-                                       Handle<ScopeInfo>(scope_info));
+      if (scope_info->is_declaration_scope()) {
+        current_scope = new (zone) DeclarationScope(
+            zone, current_scope, BLOCK_SCOPE, Handle<ScopeInfo>(scope_info));
+      } else {
+        current_scope = new (zone) Scope(zone, current_scope, BLOCK_SCOPE,
+                                         Handle<ScopeInfo>(scope_info));
+      }
     } else {
       DCHECK(context->IsCatchContext());
       String* name = context->catch_name();
       current_scope =
           new (zone) Scope(zone, current_scope,
                            ast_value_factory->GetString(handle(name, isolate)));
     }
     if (innermost_scope == NULL) innermost_scope = current_scope;
     context = context->previous();
   }
 
   script_scope->AddInnerScope(current_scope);
   script_scope->PropagateScopeInfo(false);
   return (innermost_scope == NULL) ? script_scope : innermost_scope;
 }
 
+DeclarationScope* Scope::AsDeclarationScope() {
+  DCHECK(is_declaration_scope());
+  return static_cast<DeclarationScope*>(this);
+}
+
+const DeclarationScope* Scope::AsDeclarationScope() const {
+  DCHECK(is_declaration_scope());
+  return static_cast<const DeclarationScope*>(this);
+}
+
+int Scope::num_parameters() const {
+  return is_declaration_scope() ? AsDeclarationScope()->num_parameters() : 0;
+}
 
 bool Scope::Analyze(ParseInfo* info) {
   DCHECK(info->literal() != NULL);
   DCHECK(info->scope() == NULL);
-  Scope* scope = info->literal()->scope();
-  Scope* top = scope;
+  DeclarationScope* scope = info->literal()->scope();
+  DeclarationScope* top = scope;
 
   // Traverse the scope tree up to the first unresolved scope or the global
   // scope and start scope resolution and variable allocation from that scope.
+  // Such a scope is always a closure-scope, so always skip to the next closure
+  // scope.
   while (!top->is_script_scope() &&
          !top->outer_scope()->already_resolved()) {
-    top = top->outer_scope();
+    top = top->outer_scope()->GetClosureScope();
   }
 
   // Allocate the variables.
   {
     AstNodeFactory ast_node_factory(info->ast_value_factory());
     if (!top->AllocateVariables(info, &ast_node_factory)) {
       DCHECK(top->pending_error_handler_.has_pending_error());
       top->pending_error_handler_.ThrowPendingError(info->isolate(),
                                                     info->script());
       return false;
     }
   }
 
 #ifdef DEBUG
   if (info->script_is_native() ? FLAG_print_builtin_scopes
                                : FLAG_print_scopes) {
     scope->Print();
   }
   scope->CheckScopePositions();
   scope->CheckZones();
 #endif
 
   info->set_scope(scope);
   return true;
 }
 
-void Scope::DeclareThis(AstValueFactory* ast_value_factory) {
+void DeclarationScope::DeclareThis(AstValueFactory* ast_value_factory) {
   DCHECK(!already_resolved());
   DCHECK(is_declaration_scope());
   DCHECK(has_this_declaration());
 
   bool subclass_constructor = IsSubclassConstructor(function_kind_);
   Variable* var = variables_.Declare(
       this, ast_value_factory->this_string(),
       subclass_constructor ? CONST : VAR, Variable::THIS,
       subclass_constructor ? kNeedsInitialization : kCreatedInitialized);
   receiver_ = var;
 }
 
-void Scope::DeclareDefaultFunctionVariables(
+void DeclarationScope::DeclareDefaultFunctionVariables(
     AstValueFactory* ast_value_factory) {
   DCHECK(is_function_scope());
   DCHECK(!is_arrow_scope());
   // Declare 'arguments' variable which exists in all non arrow functions.
   // Note that it might never be accessed, in which case it won't be
   // allocated during variable allocation.
   arguments_ =
       variables_.Declare(this, ast_value_factory->arguments_string(), VAR,
                          Variable::ARGUMENTS, kCreatedInitialized);
 
   new_target_ =
       variables_.Declare(this, ast_value_factory->new_target_string(), CONST,
                          Variable::NORMAL, kCreatedInitialized);
 
   if (IsConciseMethod(function_kind_) || IsClassConstructor(function_kind_) ||
       IsAccessorFunction(function_kind_)) {
     this_function_ =
         variables_.Declare(this, ast_value_factory->this_function_string(),
                            CONST, Variable::NORMAL, kCreatedInitialized);
   }
 }
 
 
 Scope* Scope::FinalizeBlockScope() {
   DCHECK(is_block_scope());
-  DCHECK(temps_.is_empty());
-  DCHECK(params_.is_empty());
 
   if (variables_.occupancy() > 0 ||
       (is_declaration_scope() && calls_sloppy_eval())) {
     return this;
   }
 
   // Remove this scope from outer scope.
   outer_scope()->RemoveInnerScope(this);
 
   // Reparent inner scopes.
@@ skipping 20 matching lines @@
     }
     outer_scope()->unresolved_ = unresolved_;
     unresolved_ = nullptr;
   }
 
   PropagateUsageFlagsToScope(outer_scope_);
 
   return NULL;
 }
 
-void Scope::Snapshot::Reparent(Scope* new_parent) const {
+void Scope::Snapshot::Reparent(DeclarationScope* new_parent) const {
   DCHECK_EQ(new_parent, outer_scope_->inner_scope_);
   DCHECK_EQ(new_parent->outer_scope_, outer_scope_);
-  DCHECK_EQ(new_parent, new_parent->ClosureScope());
+  DCHECK_EQ(new_parent, new_parent->GetClosureScope());
   DCHECK_NULL(new_parent->inner_scope_);
   DCHECK_NULL(new_parent->unresolved_);
-  DCHECK_EQ(0, new_parent->temps_.length());
+  DCHECK_EQ(0, new_parent->temps()->length());
   Scope* inner_scope = new_parent->sibling_;
   if (inner_scope != top_inner_scope_) {
     for (; inner_scope->sibling() != top_inner_scope_;
          inner_scope = inner_scope->sibling()) {
       inner_scope->outer_scope_ = new_parent;
       DCHECK_NE(inner_scope, new_parent);
     }
     inner_scope->outer_scope_ = new_parent;
 
     new_parent->inner_scope_ = new_parent->sibling_;
     inner_scope->sibling_ = nullptr;
     // Reset the sibling rather than the inner_scope_ since we
     // want to keep new_parent there.
     new_parent->sibling_ = top_inner_scope_;
   }
 
   if (outer_scope_->unresolved_ != top_unresolved_) {
     VariableProxy* last = outer_scope_->unresolved_;
     while (last->next_unresolved() != top_unresolved_) {
       last = last->next_unresolved();
     }
     last->set_next_unresolved(nullptr);
     new_parent->unresolved_ = outer_scope_->unresolved_;
     outer_scope_->unresolved_ = top_unresolved_;
   }
 
-  if (outer_scope_->ClosureScope()->temps_.length() != top_temp_) {
-    ZoneList<Variable*>* temps = &outer_scope_->ClosureScope()->temps_;
+  if (outer_scope_->GetClosureScope()->temps()->length() != top_temp_) {
+    ZoneList<Variable*>* temps = outer_scope_->GetClosureScope()->temps();
     for (int i = top_temp_; i < temps->length(); i++) {
       Variable* temp = temps->at(i);
-      DCHECK_EQ(temp->scope(), temp->scope()->ClosureScope());
+      DCHECK_EQ(temp->scope(), temp->scope()->GetClosureScope());
       DCHECK_NE(temp->scope(), new_parent);
       temp->set_scope(new_parent);
       new_parent->AddTemporary(temp);
     }
     temps->Rewind(top_temp_);
   }
 }
 
 void Scope::ReplaceOuterScope(Scope* outer) {
   DCHECK_NOT_NULL(outer);
@@ skipping 66 matching lines @@
   }
   // TODO(marja, rossberg): Correctly declare FUNCTION, CLASS, NEW_TARGET, and
   // ARGUMENTS bindings as their corresponding Variable::Kind.
 
   Variable* var = variables_.Declare(this, name, mode, kind, init_flag,
                                      maybe_assigned_flag);
   var->AllocateTo(location, index);
   return var;
 }
 
-
-Variable* Scope::LookupFunctionVar(const AstRawString* name,
-                                   AstNodeFactory* factory) {
+Variable* DeclarationScope::LookupFunctionVar(const AstRawString* name,
+                                              AstNodeFactory* factory) {
   if (function_ != NULL && function_->proxy()->raw_name() == name) {
     return function_->proxy()->var();
   } else if (!scope_info_.is_null()) {
     // If we are backed by a scope info, try to lookup the variable there.
     VariableMode mode;
     int index = scope_info_->FunctionContextSlotIndex(*(name->string()), &mode);
     if (index < 0) return NULL;
     Variable* var = new (zone())
         Variable(this, name, mode, Variable::NORMAL, kCreatedInitialized);
     DCHECK_NOT_NULL(factory);
@@ skipping 13 matching lines @@
 Variable* Scope::Lookup(const AstRawString* name) {
   for (Scope* scope = this;
        scope != NULL;
        scope = scope->outer_scope()) {
     Variable* var = scope->LookupLocal(name);
     if (var != NULL) return var;
   }
   return NULL;
 }
 
-Variable* Scope::DeclareParameter(const AstRawString* name, VariableMode mode,
-                                  bool is_optional, bool is_rest,
-                                  bool* is_duplicate,
-                                  AstValueFactory* ast_value_factory) {
+Variable* DeclarationScope::DeclareParameter(
+    const AstRawString* name, VariableMode mode, bool is_optional, bool is_rest,
+    bool* is_duplicate, AstValueFactory* ast_value_factory) {
   DCHECK(!already_resolved());
   DCHECK(is_function_scope());
   DCHECK(!is_optional || !is_rest);
   Variable* var;
   if (mode == TEMPORARY) {
     var = NewTemporary(name);
   } else {
     var = variables_.Declare(this, name, mode, Variable::NORMAL,
                              kCreatedInitialized);
     // TODO(wingo): Avoid O(n^2) check.
@@ skipping 19 matching lines @@
                               MaybeAssignedFlag maybe_assigned_flag) {
   DCHECK(!already_resolved());
   // This function handles VAR, LET, and CONST modes.  DYNAMIC variables are
   // introduced during variable allocation, and TEMPORARY variables are
   // allocated via NewTemporary().
   DCHECK(IsDeclaredVariableMode(mode));
   return variables_.Declare(this, name, mode, kind, init_flag,
                             maybe_assigned_flag);
 }
 
-
-Variable* Scope::DeclareDynamicGlobal(const AstRawString* name) {
+Variable* DeclarationScope::DeclareDynamicGlobal(const AstRawString* name) {
   DCHECK(is_script_scope());
   return variables_.Declare(this,
                             name,
                             DYNAMIC_GLOBAL,
                             Variable::NORMAL,
                             kCreatedInitialized);
 }
 
 
 bool Scope::RemoveUnresolved(VariableProxy* var) {
@@ skipping 11 matching lines @@
       return true;
     }
     current = next;
   }
   return false;
 }
 
 
 Variable* Scope::NewTemporary(const AstRawString* name) {
   DCHECK(!already_resolved());
-  Scope* scope = this->ClosureScope();
+  DeclarationScope* scope = GetClosureScope();
   Variable* var = new(zone()) Variable(scope,
                                        name,
                                        TEMPORARY,
                                        Variable::NORMAL,
                                        kCreatedInitialized);
   scope->AddTemporary(var);
   return var;
 }
 
-int Scope::RemoveTemporary(Variable* var) {
+int DeclarationScope::RemoveTemporary(Variable* var) {
   DCHECK_NOT_NULL(var);
   // Temporaries are only placed in ClosureScopes.
-  DCHECK_EQ(ClosureScope(), this);
-  DCHECK_EQ(var->scope()->ClosureScope(), var->scope());
+  DCHECK_EQ(GetClosureScope(), this);
+  DCHECK_EQ(var->scope()->GetClosureScope(), var->scope());
   // If the temporary is not here, return quickly.
   if (var->scope() != this) return -1;
   // Most likely (always?) any temporary variable we want to remove
   // was just added before, so we search backwards.
   for (int i = temps_.length(); i-- > 0;) {
     if (temps_[i] == var) {
       // Don't shrink temps_, as callers of this method expect
       // the returned indices to be unique per-scope.
       temps_[i] = nullptr;
       return i;
     }
   }
   return -1;
 }
 
 
 void Scope::AddDeclaration(Declaration* declaration) {
   decls_.Add(declaration, zone());
 }
 
 
 Declaration* Scope::CheckConflictingVarDeclarations() {
   int length = decls_.length();
   for (int i = 0; i < length; i++) {
     Declaration* decl = decls_[i];
     // We don't create a separate scope to hold the function name of a function
     // expression, so we have to make sure not to consider it when checking for
     // conflicts (since it's conceptually "outside" the declaration scope).
-    if (is_function_scope() && decl == function()) continue;
+    if (is_function_scope() && decl == AsDeclarationScope()->function())
+      continue;
     if (IsLexicalVariableMode(decl->mode()) && !is_block_scope()) continue;
     const AstRawString* name = decl->proxy()->raw_name();
 
     // Iterate through all scopes until and including the declaration scope.
     Scope* previous = NULL;
     Scope* current = decl->scope();
     // Lexical vs lexical conflicts within the same scope have already been
     // captured in Parser::Declare. The only conflicts we still need to check
     // are lexical vs VAR, or any declarations within a declaration block scope
     // vs lexical declarations in its surrounding (function) scope.
@@ skipping 47 matching lines @@
 
 void Scope::CollectStackAndContextLocals(ZoneList<Variable*>* stack_locals,
                                          ZoneList<Variable*>* context_locals,
                                          ZoneList<Variable*>* context_globals) {
   DCHECK(stack_locals != NULL);
   DCHECK(context_locals != NULL);
   DCHECK(context_globals != NULL);
 
   // Collect temporaries which are always allocated on the stack, unless the
   // context as a whole has forced context allocation.
-  for (int i = 0; i < temps_.length(); i++) {
-    Variable* var = temps_[i];
-    if (var == nullptr) continue;
-    if (var->is_used()) {
-      if (var->IsContextSlot()) {
-        DCHECK(has_forced_context_allocation());
-        context_locals->Add(var, zone());
-      } else if (var->IsStackLocal()) {
-        stack_locals->Add(var, zone());
-      } else {
-        DCHECK(var->IsParameter());
+  if (is_declaration_scope()) {
+    ZoneList<Variable*>* temps = AsDeclarationScope()->temps();
+    for (int i = 0; i < temps->length(); i++) {
+      Variable* var = (*temps)[i];
+      if (var == nullptr) continue;
+      if (var->is_used()) {
+        if (var->IsContextSlot()) {
+          DCHECK(has_forced_context_allocation());
+          context_locals->Add(var, zone());
+        } else if (var->IsStackLocal()) {
+          stack_locals->Add(var, zone());
+        } else {
+          DCHECK(var->IsParameter());
+        }
       }
     }
   }
 
   // Collect declared local variables.
   ZoneList<VarAndOrder> vars(variables_.occupancy(), zone());
   for (VariableMap::Entry* p = variables_.Start();
        p != NULL;
        p = variables_.Next(p)) {
     Variable* var = reinterpret_cast<Variable*>(p->value);
@@ skipping 94 matching lines @@
   for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
     max_context_chain_length = std::max(scope->MaxNestedContextChainLength(),
                                         max_context_chain_length);
   }
   if (NeedsContext()) {
     max_context_chain_length += 1;
   }
   return max_context_chain_length;
 }
 
-
-Scope* Scope::DeclarationScope() {
+DeclarationScope* Scope::GetDeclarationScope() {
   Scope* scope = this;
   while (!scope->is_declaration_scope()) {
     scope = scope->outer_scope();
   }
-  return scope;
+  return scope->AsDeclarationScope();
 }
 
-
-Scope* Scope::ClosureScope() {
+DeclarationScope* Scope::GetClosureScope() {
   Scope* scope = this;
   while (!scope->is_declaration_scope() || scope->is_block_scope()) {
     scope = scope->outer_scope();
   }
-  return scope;
+  return scope->AsDeclarationScope();
+}
+
+DeclarationScope* Scope::GetReceiverScope() {
+  Scope* scope = this;
+  while (!scope->is_script_scope() &&
+         (!scope->is_function_scope() ||
+          scope->AsDeclarationScope()->is_arrow_scope())) {
+    scope = scope->outer_scope();
+  }
+  return scope->AsDeclarationScope();
 }
 
 
-Scope* Scope::ReceiverScope() {
-  Scope* scope = this;
-  while (!scope->is_script_scope() &&
-         (!scope->is_function_scope() || scope->is_arrow_scope())) {
-    scope = scope->outer_scope();
-  }
-  return scope;
-}
-
-
 
 Handle<ScopeInfo> Scope::GetScopeInfo(Isolate* isolate) {
   if (scope_info_.is_null()) {
     scope_info_ = ScopeInfo::Create(isolate, zone(), this);
   }
   return scope_info_;
 }
 
 Handle<StringSet> Scope::CollectNonLocals(Handle<StringSet> non_locals) {
   // Collect non-local variables referenced in the scope.
@@ skipping 131 matching lines @@
   for (VariableMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
     Variable* var = reinterpret_cast<Variable*>(p->value);
     if (var == NULL) {
       Indent(indent, "<?>\n");
     } else {
       PrintVar(indent, var);
     }
   }
 }
 
+void DeclarationScope::PrintParameters() {
+  PrintF(" (");
+  for (int i = 0; i < params_.length(); i++) {
+    if (i > 0) PrintF(", ");
+    const AstRawString* name = params_[i]->raw_name();
+    if (name->IsEmpty())
+      PrintF(".%p", reinterpret_cast<void*>(params_[i]));
+    else
+      PrintName(name);
+  }
+  PrintF(")");
+}
 
 void Scope::Print(int n) {
   int n0 = (n > 0 ? n : 0);
   int n1 = n0 + 2;  // indentation
 
   // Print header.
-  Indent(n0, Header(scope_type_, function_kind_, is_declaration_scope()));
+  FunctionKind function_kind = is_function_scope()
+                                   ? AsDeclarationScope()->function_kind()
+                                   : kNormalFunction;
+  Indent(n0, Header(scope_type_, function_kind, is_declaration_scope()));
   if (scope_name_ != nullptr && !scope_name_->IsEmpty()) {
     PrintF(" ");
     PrintName(scope_name_);
   }
 
   // Print parameters, if any.
+  VariableDeclaration* function = nullptr;
   if (is_function_scope()) {
-    PrintF(" (");
-    for (int i = 0; i < params_.length(); i++) {
-      if (i > 0) PrintF(", ");
-      const AstRawString* name = params_[i]->raw_name();
-      if (name->IsEmpty())
-        PrintF(".%p", reinterpret_cast<void*>(params_[i]));
-      else
-        PrintName(name);
-    }
-    PrintF(")");
+    AsDeclarationScope()->PrintParameters();
+    function = AsDeclarationScope()->function();
   }
 
   PrintF(" { // (%d, %d)\n", start_position(), end_position());
 
   // Function name, if any (named function literals, only).
-  if (function_ != NULL) {
+  if (function != nullptr) {
     Indent(n1, "// (local) function name: ");
-    PrintName(function_->proxy()->raw_name());
+    PrintName(function->proxy()->raw_name());
     PrintF("\n");
   }
 
   // Scope info.
   if (HasTrivialOuterContext()) {
     Indent(n1, "// scope has trivial outer context\n");
   }
   if (is_strict(language_mode())) {
     Indent(n1, "// strict mode scope\n");
   }
@@ skipping 11 matching lines @@
     Indent(n1, "// ");
     PrintF("%d stack slots\n", num_stack_slots_);
   }
   if (num_heap_slots_ > 0) {
     Indent(n1, "// ");
     PrintF("%d heap slots (including %d global slots)\n", num_heap_slots_,
            num_global_slots_);
   }
 
   // Print locals.
-  if (function_ != NULL) {
+  if (function != nullptr) {
     Indent(n1, "// function var:\n");
-    PrintVar(n1, function_->proxy()->var());
+    PrintVar(n1, function->proxy()->var());
   }
 
-  if (temps_.length() > 0) {
+  if (is_declaration_scope()) {
     bool printed_header = false;
-    for (int i = 0; i < temps_.length(); i++) {
-      if (temps_[i] != nullptr) {
+    ZoneList<Variable*>* temps = AsDeclarationScope()->temps();
+    for (int i = 0; i < temps->length(); i++) {
+      if ((*temps)[i] != nullptr) {
         if (!printed_header) {
           printed_header = true;
           Indent(n1, "// temporary vars:\n");
         }
-        PrintVar(n1, temps_[i]);
+        PrintVar(n1, (*temps)[i]);
       }
     }
   }
 
   if (variables_.Start() != NULL) {
     Indent(n1, "// local vars:\n");
     PrintMap(n1, &variables_);
   }
 
   if (dynamics_ != NULL) {
@@ skipping 70 matching lines @@
   Variable* var = LookupLocal(proxy->raw_name());
 
   // We found a variable and we are done. (Even if there is an 'eval' in
   // this scope which introduces the same variable again, the resulting
   // variable remains the same.)
   if (var != NULL) {
     *binding_kind = BOUND;
     return var;
   }
 
-  // We did not find a variable locally. Check against the function variable,
-  // if any. We can do this for all scopes, since the function variable is
-  // only present - if at all - for function scopes.
+  // We did not find a variable locally. Check against the function variable, if
+  // any.
   *binding_kind = UNBOUND;
-  var = LookupFunctionVar(proxy->raw_name(), factory);
+  var =
+      is_function_scope()
+          ? AsDeclarationScope()->LookupFunctionVar(proxy->raw_name(), factory)
+          : nullptr;
   if (var != NULL) {
     *binding_kind = BOUND;
   } else if (outer_scope_ != nullptr && this != max_outer_scope) {
     var = outer_scope_->LookupRecursive(proxy, binding_kind, factory,
                                         max_outer_scope);
     if (*binding_kind == BOUND && (is_function_scope() || is_with_scope())) {
       var->ForceContextAllocation();
     }
   } else {
     DCHECK(is_script_scope() || this == max_outer_scope);
@@ skipping 202 matching lines @@
   if (var->mode() == TEMPORARY) return false;
   if (is_catch_scope() || is_module_scope()) return true;
   if (is_script_scope() && IsLexicalVariableMode(var->mode())) return true;
   return var->has_forced_context_allocation() || scope_calls_eval_ ||
          inner_scope_calls_eval_;
 }
 
 
 void Scope::AllocateStackSlot(Variable* var) {
   if (is_block_scope()) {
-    outer_scope()->DeclarationScope()->AllocateStackSlot(var);
+    outer_scope()->GetDeclarationScope()->AllocateStackSlot(var);
   } else {
     var->AllocateTo(VariableLocation::LOCAL, num_stack_slots_++);
   }
 }
 
 
 void Scope::AllocateHeapSlot(Variable* var) {
   var->AllocateTo(VariableLocation::CONTEXT, num_heap_slots_++);
 }
 
-void Scope::AllocateParameterLocals() {
+void DeclarationScope::AllocateParameterLocals() {
   DCHECK(is_function_scope());
 
   bool uses_sloppy_arguments = false;
 
   // Functions have 'arguments' declared implicitly in all non arrow functions.
   if (arguments_ != nullptr) {
     // 'arguments' is used. Unless there is also a parameter called
     // 'arguments', we must be conservative and allocate all parameters to
     // the context assuming they will be captured by the arguments object.
     // If we have a parameter named 'arguments', a (new) value is always
@@ skipping 32 matching lines @@
 
     DCHECK(var->scope() == this);
     if (uses_sloppy_arguments || has_forced_context_allocation()) {
       // Force context allocation of the parameter.
       var->ForceContextAllocation();
     }
     AllocateParameter(var, i);
   }
 }
 
-
-void Scope::AllocateParameter(Variable* var, int index) {
+void DeclarationScope::AllocateParameter(Variable* var, int index) {
   if (MustAllocate(var)) {
     if (MustAllocateInContext(var)) {
       DCHECK(var->IsUnallocated() || var->IsContextSlot());
       if (var->IsUnallocated()) {
         AllocateHeapSlot(var);
       }
     } else {
       DCHECK(var->IsUnallocated() || var->IsParameter());
       if (var->IsUnallocated()) {
         var->AllocateTo(VariableLocation::PARAMETER, index);
       }
     }
   } else {
     DCHECK(!var->IsGlobalSlot());
   }
 }
 
-
-void Scope::AllocateReceiver() {
+void DeclarationScope::AllocateReceiver() {
+  if (!has_this_declaration()) return;
   DCHECK_NOT_NULL(receiver());
   DCHECK_EQ(receiver()->scope(), this);
 
   if (has_forced_context_allocation()) {
     // Force context allocation of the receiver.
     receiver()->ForceContextAllocation();
   }
   AllocateParameter(receiver(), -1);
 }
 
@@ skipping 25 matching lines @@
     } else {
       // There must be only DYNAMIC_GLOBAL in the script scope.
       DCHECK(!is_script_scope() || DYNAMIC_GLOBAL == var->mode());
     }
   }
 }
 
 void Scope::AllocateNonParameterLocalsAndDeclaredGlobals(
     AstValueFactory* ast_value_factory) {
   // All variables that have no rewrite yet are non-parameter locals.
-  for (int i = 0; i < temps_.length(); i++) {
-    if (temps_[i] == nullptr) continue;
-    AllocateNonParameterLocal(temps_[i], ast_value_factory);
+  if (is_declaration_scope()) {
+    ZoneList<Variable*>* temps = AsDeclarationScope()->temps();
+    for (int i = 0; i < temps->length(); i++) {
+      if ((*temps)[i] == nullptr) continue;
+      AllocateNonParameterLocal((*temps)[i], ast_value_factory);
+    }
   }
 
   ZoneList<VarAndOrder> vars(variables_.occupancy(), zone());
   for (VariableMap::Entry* p = variables_.Start();
        p != NULL;
        p = variables_.Next(p)) {
     Variable* var = reinterpret_cast<Variable*>(p->value);
     vars.Add(VarAndOrder(var, p->order), zone());
   }
   vars.Sort(VarAndOrder::Compare);
   int var_count = vars.length();
   for (int i = 0; i < var_count; i++) {
     AllocateNonParameterLocal(vars[i].var(), ast_value_factory);
   }
 
   if (FLAG_global_var_shortcuts) {
     for (int i = 0; i < var_count; i++) {
       AllocateDeclaredGlobal(vars[i].var(), ast_value_factory);
     }
   }
 
+  if (is_declaration_scope()) {
+    AsDeclarationScope()->AllocateLocals(ast_value_factory);
+  }
+}
+
+void DeclarationScope::AllocateLocals(AstValueFactory* ast_value_factory) {
   // For now, function_ must be allocated at the very end.  If it gets
   // allocated in the context, it must be the last slot in the context,
   // because of the current ScopeInfo implementation (see
   // ScopeInfo::ScopeInfo(FunctionScope* scope) constructor).
   if (function_ != nullptr) {
     AllocateNonParameterLocal(function_->proxy()->var(), ast_value_factory);
   }
 
   if (rest_parameter_ != nullptr) {
     AllocateNonParameterLocal(rest_parameter_, ast_value_factory);
@@ skipping 18 matching lines @@
   }
 
   // If scope is already resolved, we still need to allocate
   // variables in inner scopes which might not have been resolved yet.
   if (already_resolved()) return;
   // The number of slots required for variables.
   num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;
 
   // Allocate variables for this scope.
   // Parameters must be allocated first, if any.
-  if (is_function_scope()) AllocateParameterLocals();
-  if (has_this_declaration()) AllocateReceiver();
+  if (is_declaration_scope()) {
+    if (is_function_scope()) AsDeclarationScope()->AllocateParameterLocals();
+    AsDeclarationScope()->AllocateReceiver();
+  }
   AllocateNonParameterLocalsAndDeclaredGlobals(ast_value_factory);
 
   // Force allocation of a context for this scope if necessary. For a 'with'
   // scope and for a function scope that makes an 'eval' call we need a context,
   // even if no local variables were statically allocated in the scope.
   // Likewise for modules.
   bool must_have_context =
       is_with_scope() || is_module_scope() ||
       (is_function_scope() && calls_sloppy_eval()) ||
       (is_block_scope() && is_declaration_scope() && calls_sloppy_eval());
 
   // If we didn't allocate any locals in the local context, then we only
   // need the minimal number of slots if we must have a context.
   if (num_heap_slots_ == Context::MIN_CONTEXT_SLOTS && !must_have_context) {
     num_heap_slots_ = 0;
   }
 
   // Allocation done.
   DCHECK(num_heap_slots_ == 0 || num_heap_slots_ >= Context::MIN_CONTEXT_SLOTS);
 }
 
 
 int Scope::StackLocalCount() const {
+  VariableDeclaration* function =
+      is_function_scope() ? AsDeclarationScope()->function() : nullptr;
   return num_stack_slots() -
-      (function_ != NULL && function_->proxy()->var()->IsStackLocal() ? 1 : 0);
+         (function != NULL && function->proxy()->var()->IsStackLocal() ? 1 : 0);
 }
 
 
 int Scope::ContextLocalCount() const {
   if (num_heap_slots() == 0) return 0;
+  VariableDeclaration* function =
+      is_function_scope() ? AsDeclarationScope()->function() : nullptr;
   bool is_function_var_in_context =
-      function_ != NULL && function_->proxy()->var()->IsContextSlot();
+      function != NULL && function->proxy()->var()->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS - num_global_slots() -
          (is_function_var_in_context ? 1 : 0);
 }
 
 
 int Scope::ContextGlobalCount() const { return num_global_slots(); }
 
 }  // namespace internal
 }  // namespace v8