[es6] implement optional parameters via desugaring (with scoping)

src/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/v8.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parser.h"
@@ skipping 59 matching lines @@
 // ----------------------------------------------------------------------------
 // Implementation of Scope
 
 Scope::Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type,
              AstValueFactory* ast_value_factory, FunctionKind function_kind)
     : inner_scopes_(4, zone),
       variables_(zone),
       internals_(4, zone),
       temps_(4, zone),
       params_(4, zone),
+      param_positions_(4, zone),
       unresolved_(16, zone),
       decls_(4, zone),
       module_descriptor_(
           scope_type == MODULE_SCOPE ? ModuleDescriptor::New(zone) : NULL),
       already_resolved_(false),
       ast_value_factory_(ast_value_factory),
       zone_(zone),
       class_declaration_group_start_(-1) {
   SetDefaults(scope_type, outer_scope, Handle<ScopeInfo>::null(),
               function_kind);
   // The outermost scope must be a script scope.
   DCHECK(scope_type == SCRIPT_SCOPE || outer_scope != NULL);
   DCHECK(!HasIllegalRedeclaration());
 }
 
 
 Scope::Scope(Zone* zone, Scope* inner_scope, ScopeType scope_type,
              Handle<ScopeInfo> scope_info, AstValueFactory* value_factory)
     : inner_scopes_(4, zone),
       variables_(zone),
       internals_(4, zone),
       temps_(4, zone),
       params_(4, zone),
+      param_positions_(4, zone),
       unresolved_(16, zone),
       decls_(4, zone),
       module_descriptor_(NULL),
       already_resolved_(true),
       ast_value_factory_(value_factory),
       zone_(zone),
       class_declaration_group_start_(-1) {
   SetDefaults(scope_type, NULL, scope_info);
   if (!scope_info.is_null()) {
     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);
 }
 
 
 Scope::Scope(Zone* zone, Scope* inner_scope,
              const AstRawString* catch_variable_name,
              AstValueFactory* value_factory)
     : inner_scopes_(1, zone),
       variables_(zone),
       internals_(0, zone),
       temps_(0, zone),
       params_(0, zone),
+      param_positions_(0, zone),
       unresolved_(0, zone),
       decls_(0, zone),
       module_descriptor_(NULL),
       already_resolved_(true),
       ast_value_factory_(value_factory),
       zone_(zone),
       class_declaration_group_start_(-1) {
   SetDefaults(CATCH_SCOPE, NULL, Handle<ScopeInfo>::null());
   AddInnerScope(inner_scope);
   ++num_var_or_const_;
   num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;
   Variable* variable = variables_.Declare(this,
                                           catch_variable_name,
                                           VAR,
                                           Variable::NORMAL,
                                           kCreatedInitialized);
   AllocateHeapSlot(variable);
 }
 
 
 void Scope::SetDefaults(ScopeType scope_type, Scope* outer_scope,
                         Handle<ScopeInfo> scope_info,
                         FunctionKind function_kind) {
   outer_scope_ = outer_scope;
+  function_body_ = nullptr;
   scope_type_ = scope_type;
   function_kind_ = function_kind;
   block_scope_is_class_scope_ = false;
   scope_name_ = ast_value_factory_->empty_string();
   dynamics_ = NULL;
   receiver_ = NULL;
   new_target_ = nullptr;
   function_ = NULL;
   arguments_ = NULL;
   illegal_redecl_ = NULL;
@@ skipping 24 matching lines @@
   rest_index_ = -1;
   scope_info_ = scope_info;
   start_position_ = RelocInfo::kNoPosition;
   end_position_ = RelocInfo::kNoPosition;
   if (!scope_info.is_null()) {
     scope_calls_eval_ = scope_info->CallsEval();
     language_mode_ = scope_info->language_mode();
     block_scope_is_class_scope_ = scope_info->block_scope_is_class_scope();
     function_kind_ = scope_info->function_kind();
   }
+  if (scope_type == FUNCTION_BODY_SCOPE) {
+    DCHECK_NOT_NULL(outer_scope);
+    DCHECK(outer_scope->is_function_scope());
+    DCHECK_NULL(outer_scope->function_body_);
+    outer_scope->function_body_ = this;
+  }
 }
 
 
 Scope* Scope::DeserializeScopeChain(Isolate* isolate, Zone* zone,
                                     Context* context, Scope* script_scope) {
   // Reconstruct the outer scope chain from a closure's context chain.
   Scope* current_scope = NULL;
   Scope* innermost_scope = NULL;
   bool contains_with = false;
   while (!context->IsNativeContext()) {
@@ skipping 103 matching lines @@
   }
 
   // Declare convenience variables.
   // Declare and allocate receiver (even for the script scope, and even
   // if naccesses_ == 0).
   // NOTE: When loading parameters in the script scope, we must take
   // care not to access them as properties of the global object, but
   // instead load them directly from the stack. Currently, the only
   // such parameter is 'this' which is passed on the stack when
   // invoking scripts
-  if (is_declaration_scope()) {
+  if (is_declaration_scope() && !is_function_body_scope()) {
     DCHECK(!subclass_constructor || is_function_scope());
     Variable* var = variables_.Declare(
         this, ast_value_factory_->this_string(),
         subclass_constructor ? CONST : VAR, Variable::THIS,
         subclass_constructor ? kNeedsInitialization : kCreatedInitialized);
     var->AllocateTo(Variable::PARAMETER, -1);
     receiver_ = var;
 
     if (subclass_constructor) {
       new_target_ =
@@ skipping 21 matching lines @@
 
 
 Scope* Scope::FinalizeBlockScope() {
   DCHECK(is_block_scope());
   DCHECK(internals_.is_empty());
   DCHECK(temps_.is_empty());
   DCHECK(params_.is_empty());
 
   if (num_var_or_const() > 0) return this;
 
+  // If this is the function body scope of a function scope, remove the parent
+  // function body.
+  if (outer_scope_->function_body_ == this) {
+    outer_scope_->function_body_ = nullptr;
+  }
+
   // Remove this scope from outer scope.
   for (int i = 0; i < outer_scope_->inner_scopes_.length(); i++) {
     if (outer_scope_->inner_scopes_[i] == this) {
       outer_scope_->inner_scopes_.Remove(i);
       break;
     }
   }
 
   // Reparent inner scopes.
   for (int i = 0; i < inner_scopes_.length(); i++) {
@@ skipping 85 matching lines @@
        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_rest, bool* is_duplicate) {
+                                  int pos, bool is_rest, bool* is_duplicate) {
   DCHECK(!already_resolved());
   DCHECK(is_function_scope());
   Variable* var = variables_.Declare(this, name, mode, Variable::NORMAL,
                                      kCreatedInitialized);
   if (is_rest) {
     DCHECK_NULL(rest_parameter_);
     rest_parameter_ = var;
     rest_index_ = num_parameters();
   }
   // TODO(wingo): Avoid O(n^2) check.
   *is_duplicate = IsDeclaredParameter(name);
   params_.Add(var, zone());
+  param_positions_.Add(pos, zone());
   return var;
 }
 
 
 Variable* Scope::DeclareLocal(const AstRawString* name, VariableMode mode,
                               InitializationFlag init_flag, Variable::Kind kind,
                               MaybeAssignedFlag maybe_assigned_flag,
                               int declaration_group_start) {
   DCHECK(!already_resolved());
   // This function handles VAR, LET, and CONST modes.  DYNAMIC variables are
   // introduces during variable allocation, INTERNAL variables are allocated
   // explicitly, and TEMPORARY variables are allocated via NewTemporary().
   DCHECK(IsDeclaredVariableMode(mode));
   ++num_var_or_const_;
   return variables_.Declare(this, name, mode, kind, init_flag,
                             maybe_assigned_flag, declaration_group_start);
 }
 
 
+Variable* Scope::RedeclareLocal(const AstRawString* name, VariableMode mode,
+                                InitializationFlag init_flag,
+                                Variable::Kind kind,
+                                MaybeAssignedFlag maybe_assigned_flag,
+                                int declaration_group_start) {
+  variables_.Remove(const_cast<AstRawString*>(name), name->hash());
+  return DeclareLocal(name, mode, init_flag, kind, maybe_assigned_flag,
+                      declaration_group_start);
+}
+
+
 Variable* Scope::DeclareDynamicGlobal(const AstRawString* name) {
   DCHECK(is_script_scope());
   return variables_.Declare(this,
                             name,
                             DYNAMIC_GLOBAL,
                             Variable::NORMAL,
                             kCreatedInitialized);
 }
 
 
@@ skipping 27 matching lines @@
                                        name,
                                        TEMPORARY,
                                        Variable::NORMAL,
                                        kCreatedInitialized);
   temps_.Add(var, zone());
   return var;
 }
 
 
 void Scope::AddDeclaration(Declaration* declaration) {
-  decls_.Add(declaration, zone());
+  Scope* target = this;
+  if (is_function_body_scope() &&
+      (declaration->mode() == VAR || declaration->IsFunctionDeclaration())) {
+    // Add `var` declarations to outer scope, to make allocation simpler
+    target = outer_scope();
+    DCHECK(target->is_function_scope());
+  }
+  target->decls_.Add(declaration, zone());
 }
 
 
 void Scope::SetIllegalRedeclaration(Expression* expression) {
   // Record only the first illegal redeclaration.
   if (!HasIllegalRedeclaration()) {
     illegal_redecl_ = expression;
   }
   DCHECK(HasIllegalRedeclaration());
 }
@@ skipping 154 matching lines @@
 
 bool Scope::HasLazyCompilableOuterContext() const {
   Scope* outer = outer_scope_;
   if (outer == NULL) return true;
   // We have to prevent lazy compilation if this scope is inside a with scope
   // and all declaration scopes between them have empty contexts. Such
   // declaration scopes may become invisible during scope info deserialization.
   outer = outer->DeclarationScope();
   bool found_non_trivial_declarations = false;
   for (const Scope* scope = outer; scope != NULL; scope = scope->outer_scope_) {
-    if (scope->is_with_scope() && !found_non_trivial_declarations) return false;
+    if ((scope->is_function_body_scope() || scope->is_with_scope()) &&
+        !found_non_trivial_declarations)
+      return false;
     if (scope->is_block_scope() && !scope->decls_.is_empty()) return false;
     if (scope->is_declaration_scope() && scope->num_heap_slots() > 0) {
       found_non_trivial_declarations = true;
     }
   }
   return true;
 }
 
 
 bool Scope::AllowsLazyCompilation() const {
@@ skipping 80 matching lines @@
 static const char* Header(ScopeType scope_type) {
   switch (scope_type) {
     case EVAL_SCOPE: return "eval";
     case FUNCTION_SCOPE: return "function";
     case MODULE_SCOPE: return "module";
     case SCRIPT_SCOPE: return "global";
     case CATCH_SCOPE: return "catch";
     case BLOCK_SCOPE: return "block";
     case WITH_SCOPE: return "with";
     case ARROW_SCOPE: return "arrow";
+    case FUNCTION_BODY_SCOPE:
+      return "function body";
   }
   UNREACHABLE();
   return NULL;
 }
 
 
 static void Indent(int n, const char* str) {
   PrintF("%*s%s", n, "", str);
 }
 
@@ skipping 182 matching lines @@
 Variable* Scope::LookupRecursive(VariableProxy* proxy,
                                  BindingKind* binding_kind,
                                  AstNodeFactory* factory) {
   DCHECK(binding_kind != NULL);
   if (already_resolved() && is_with_scope()) {
     // Short-cut: if the scope is deserialized from a scope info, variable
     // allocation is already fixed.  We can simply return with dynamic lookup.
     *binding_kind = DYNAMIC_LOOKUP;
     return NULL;
   }
-
   // Try to find the variable in this scope.
   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;
   }
@@ skipping 36 matching lines @@
       *binding_kind = UNBOUND_EVAL_SHADOWED;
     }
   }
   return var;
 }
 
 
 bool Scope::ResolveVariable(ParseInfo* info, VariableProxy* proxy,
                             AstNodeFactory* factory) {
   DCHECK(info->script_scope()->is_script_scope());
-
   // If the proxy is already resolved there's nothing to do
   // (functions and consts may be resolved by the parser).
   if (proxy->is_resolved()) return true;
 
   // Otherwise, try to resolve the variable.
   BindingKind binding_kind;
   Variable* var = LookupRecursive(proxy, &binding_kind, factory);
   switch (binding_kind) {
     case BOUND:
       // We found a variable binding.
@@ skipping 257 matching lines @@
     if (params_[i]->name().is_identical_to(
             isolate->factory()->arguments_string())) {
       return true;
     }
   }
   return false;
 }
 
 
 void Scope::AllocateStackSlot(Variable* var) {
-  if (is_block_scope()) {
+  if (is_function_body_scope()) {
+    // Function body variables need to be allocated in the "real" function
+    // scope, but can't be resolved from it
+    outer_scope()->AllocateStackSlot(var);
+  } else if (is_block_scope()) {
     DeclarationScope()->AllocateStackSlot(var);
   } else {
     var->AllocateTo(Variable::LOCAL, num_stack_slots_++);
   }
 }
 
 
 void Scope::AllocateHeapSlot(Variable* var) {
+  DCHECK(!is_function_body_scope() || var->scope() == outer_scope());
+  if (is_function_body_scope()) return outer_scope()->AllocateHeapSlot(var);
   var->AllocateTo(Variable::CONTEXT, num_heap_slots_++);
 }
 
 
 void Scope::AllocateParameterLocals(Isolate* isolate) {
   DCHECK(is_function_scope());
   Variable* arguments = LookupLocal(ast_value_factory_->arguments_string());
   // Functions have 'arguments' declared implicitly in all non arrow functions.
   DCHECK(arguments != nullptr || is_arrow_scope());
 
@@ skipping 49 matching lines @@
         if (var->IsUnallocated()) {
           var->AllocateTo(Variable::PARAMETER, i);
         }
       }
     }
   }
 }
 
 
 void Scope::AllocateNonParameterLocal(Isolate* isolate, Variable* var) {
-  DCHECK(var->scope() == this);
+  DCHECK(var->scope() == this ||
+         (is_function_body_scope() && var->scope() == outer_scope()));
   DCHECK(!var->IsVariable(isolate->factory()->dot_result_string()) ||
          !var->IsStackLocal());
   if (var->IsUnallocated() && MustAllocate(var)) {
     if (MustAllocateInContext(var)) {
       AllocateHeapSlot(var);
     } else {
       AllocateStackSlot(var);
     }
   }
 }
@@ skipping 84 matching lines @@
       DCHECK(scope->module_descriptor_->IsFrozen());
       DCHECK_NULL(scope->module_var_);
       scope->module_var_ = NewInternal(ast_value_factory_->dot_module_string());
       ++num_modules_;
     }
   }
 }
 
 
 int Scope::StackLocalCount() const {
+  DCHECK(!function_body() || function_body()->num_stack_slots() == 0);
   return num_stack_slots() -
       (function_ != NULL && function_->proxy()->var()->IsStackLocal() ? 1 : 0);
 }
 
 
 int Scope::ContextLocalCount() const {
+  DCHECK(!function_body() || function_body()->num_heap_slots() == 0);
   if (num_heap_slots() == 0) return 0;
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
       (function_ != NULL && function_->proxy()->var()->IsContextSlot() ? 1 : 0);
 }
 } }  // namespace v8::internal