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// 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.
#ifndef V8_AST_SCOPES_H_
#define V8_AST_SCOPES_H_
#include "src/ast/ast.h"
#include "src/base/compiler-specific.h"
#include "src/base/hashmap.h"
#include "src/globals.h"
#include "src/objects.h"
#include "src/zone/zone.h"
namespace v8 {
namespace internal {
class AstNodeFactory;
class AstValueFactory;
class AstRawString;
class Declaration;
class ParseInfo;
class PreParsedScopeData;
class ProducedPreParsedScopeData;
class SloppyBlockFunctionStatement;
class Statement;
class StringSet;
class VariableProxy;
// A hash map to support fast variable declaration and lookup.
class VariableMap: public ZoneHashMap {
explicit VariableMap(Zone* zone);
Variable* Declare(
Zone* zone, Scope* scope, const AstRawString* name, VariableMode mode,
VariableKind kind = NORMAL_VARIABLE,
InitializationFlag initialization_flag = kCreatedInitialized,
MaybeAssignedFlag maybe_assigned_flag = kNotAssigned,
bool* added = nullptr);
// Records that "name" exists (if not recorded yet) but doesn't create a
// Variable. Useful for preparsing.
Variable* DeclareName(Zone* zone, const AstRawString* name,
VariableMode mode);
Variable* Lookup(const AstRawString* name);
void Remove(Variable* var);
void Add(Zone* zone, Variable* var);
// Sloppy block-scoped function declarations to var-bind
class SloppyBlockFunctionMap : public ZoneHashMap {
class Delegate : public ZoneObject {
Delegate(Scope* scope, SloppyBlockFunctionStatement* statement, int index)
: scope_(scope), statement_(statement), next_(nullptr), index_(index) {}
void set_statement(Statement* statement);
void set_next(Delegate* next) { next_ = next; }
Delegate* next() const { return next_; }
Scope* scope() const { return scope_; }
int index() const { return index_; }
Scope* scope_;
SloppyBlockFunctionStatement* statement_;
Delegate* next_;
int index_;
explicit SloppyBlockFunctionMap(Zone* zone);
void Declare(Zone* zone, const AstRawString* name, Scope* scope,
SloppyBlockFunctionStatement* statement);
int count_;
enum class AnalyzeMode { kRegular, kDebugger };
// Global invariants after AST construction: Each reference (i.e. identifier)
// to a JavaScript variable (including global properties) is represented by a
// VariableProxy node. Immediately after AST construction and before variable
// allocation, most VariableProxy nodes are "unresolved", i.e. not bound to a
// corresponding variable (though some are bound during parse time). Variable
// allocation binds each unresolved VariableProxy to one Variable and assigns
// a location. Note that many VariableProxy nodes may refer to the same Java-
// Script variable.
// 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 V8_EXPORT_PRIVATE Scope : public NON_EXPORTED_BASE(ZoneObject) {
// ---------------------------------------------------------------------------
// Construction
Scope(Zone* zone, Scope* outer_scope, ScopeType scope_type);
#ifdef DEBUG
// The scope name is only used for printing/debugging.
void SetScopeName(const AstRawString* scope_name) {
scope_name_ = scope_name;
void set_needs_migration() { needs_migration_ = true; }
// TODO(verwaest): Is this needed on Scope?
int num_parameters() const;
DeclarationScope* AsDeclarationScope();
const DeclarationScope* AsDeclarationScope() const;
ModuleScope* AsModuleScope();
const ModuleScope* AsModuleScope() const;
class Snapshot final BASE_EMBEDDED {
explicit Snapshot(Scope* scope);
void Reparent(DeclarationScope* new_parent) const;
Scope* outer_scope_;
Scope* top_inner_scope_;
VariableProxy* top_unresolved_;
ThreadedList<Variable>::Iterator top_local_;
ThreadedList<Declaration>::Iterator top_decl_;
const bool outer_scope_calls_eval_;
enum class DeserializationMode { kIncludingVariables, kScopesOnly };
static Scope* DeserializeScopeChain(Zone* zone, ScopeInfo* scope_info,
DeclarationScope* script_scope,
AstValueFactory* ast_value_factory,
DeserializationMode deserialization_mode);
// Checks if the block scope is redundant, i.e. it does not contain any
// block scoped declarations. In that case it is removed from the scope
// tree and its children are reparented.
Scope* FinalizeBlockScope();
bool HasBeenRemoved() const;
// Find the first scope that hasn't been removed.
Scope* GetUnremovedScope();
// Inserts outer_scope into this scope's scope chain (and removes this
// from the current outer_scope_'s inner scope list).
// Assumes outer_scope_ is non-null.
void ReplaceOuterScope(Scope* outer_scope);
Zone* zone() const { return zone_; }
void SetMustUsePreParsedScopeData() {
if (must_use_preparsed_scope_data_) {
must_use_preparsed_scope_data_ = true;
if (outer_scope_) {
bool must_use_preparsed_scope_data() const {
return must_use_preparsed_scope_data_;
// ---------------------------------------------------------------------------
// Declarations
// Lookup a variable in this scope. Returns the variable or nullptr if not
// found.
Variable* LookupLocal(const AstRawString* name) {
Variable* result = variables_.Lookup(name);
if (result != nullptr || scope_info_.is_null()) return result;
return LookupInScopeInfo(name);
Variable* LookupInScopeInfo(const AstRawString* name);
// Lookup a variable in this scope or outer scopes.
// Returns the variable or nullptr if not found.
Variable* Lookup(const AstRawString* name);
// Declare a local variable in this scope. If the variable has been
// declared before, the previously declared variable is returned.
Variable* DeclareLocal(const AstRawString* name, VariableMode mode,
InitializationFlag init_flag = kCreatedInitialized,
VariableKind kind = NORMAL_VARIABLE,
MaybeAssignedFlag maybe_assigned_flag = kNotAssigned);
Variable* DeclareVariable(Declaration* declaration, VariableMode mode,
InitializationFlag init,
bool* sloppy_mode_block_scope_function_redefinition,
bool* ok);
// The return value is meaningful only if FLAG_preparser_scope_analysis is on.
Variable* DeclareVariableName(const AstRawString* name, VariableMode mode);
void DeclareCatchVariableName(const AstRawString* name);
// Declarations list.
ThreadedList<Declaration>* declarations() { return &decls_; }
ThreadedList<Variable>* locals() { return &locals_; }
// Create a new unresolved variable.
VariableProxy* NewUnresolved(AstNodeFactory* factory,
const AstRawString* name,
int start_pos = kNoSourcePosition,
VariableKind kind = NORMAL_VARIABLE) {
// Note that we must not share the unresolved variables with
// the same name because they may be removed selectively via
// RemoveUnresolved().
DCHECK_EQ(factory->zone(), zone());
VariableProxy* proxy = factory->NewVariableProxy(name, kind, start_pos);
unresolved_ = proxy;
return proxy;
void AddUnresolved(VariableProxy* proxy);
// Remove a unresolved variable. During parsing, an unresolved variable
// may have been added optimistically, but then only the variable name
// was used (typically for labels). If the variable was not declared, the
// addition introduced a new unresolved variable which may end up being
// allocated globally as a "ghost" variable. RemoveUnresolved removes
// such a variable again if it was added; otherwise this is a no-op.
bool RemoveUnresolved(VariableProxy* var);
// Creates a new temporary variable in this scope's TemporaryScope. The
// name is only used for printing and cannot be used to find the variable.
// In particular, the only way to get hold of the temporary is by keeping the
// Variable* around. The name should not clash with a legitimate variable
// names.
// TODO(verwaest): Move to DeclarationScope?
Variable* NewTemporary(const AstRawString* name);
// ---------------------------------------------------------------------------
// Illegal redeclaration support.
// Check if the scope has conflicting var
// declarations, i.e. a var declaration that has been hoisted from a nested
// scope over a let binding of the same name.
Declaration* CheckConflictingVarDeclarations();
// Check if the scope has a conflicting lexical declaration that has a name in
// the given list. This is used to catch patterns like
// `try{}catch(e){let e;}`,
// which is an error even though the two 'e's are declared in different
// scopes.
Declaration* CheckLexDeclarationsConflictingWith(
const ZoneList<const AstRawString*>& names);
// ---------------------------------------------------------------------------
// Scope-specific info.
// Inform the scope and outer scopes that the corresponding code contains an
// eval call.
void RecordEvalCall() {
scope_calls_eval_ = true;
void RecordInnerScopeEvalCall() {
inner_scope_calls_eval_ = true;
for (Scope* scope = outer_scope(); scope != nullptr;
scope = scope->outer_scope()) {
if (scope->inner_scope_calls_eval_) {
scope->inner_scope_calls_eval_ = true;
// Set the language mode flag (unless disabled by a global flag).
void SetLanguageMode(LanguageMode language_mode) {
DCHECK(!is_module_scope() || is_strict(language_mode));
// Inform the scope that the scope may execute declarations nonlinearly.
// Currently, the only nonlinear scope is a switch statement. The name is
// more general in case something else comes up with similar control flow,
// for example the ability to break out of something which does not have
// its own lexical scope.
// The bit does not need to be stored on the ScopeInfo because none of
// the three compilers will perform hole check elimination on a variable
// located in VariableLocation::CONTEXT. So, direct eval and closures
// will not expose holes.
void SetNonlinear() { scope_nonlinear_ = true; }
// Position in the source where this scope begins and ends.
// * For the scope of a with statement
// with (obj) stmt
// start position: start position of first token of 'stmt'
// end position: end position of last token of 'stmt'
// * For the scope of a block
// { stmts }
// start position: start position of '{'
// end position: end position of '}'
// * For the scope of a function literal or decalaration
// function fun(a,b) { stmts }
// start position: start position of '('
// end position: end position of '}'
// * For the scope of a catch block
// try { stms } catch(e) { stmts }
// start position: start position of '('
// end position: end position of ')'
// * For the scope of a for-statement
// for (let x ...) stmt
// start position: start position of '('
// end position: end position of last token of 'stmt'
// * For the scope of a switch statement
// switch (tag) { cases }
// start position: start position of '{'
// end position: end position of '}'
int start_position() const { return start_position_; }
void set_start_position(int statement_pos) {
start_position_ = statement_pos;
int end_position() const { return end_position_; }
void set_end_position(int statement_pos) {
end_position_ = statement_pos;
// Scopes created for desugaring are hidden. I.e. not visible to the debugger.
bool is_hidden() const { return is_hidden_; }
void set_is_hidden() { is_hidden_ = true; }
void ForceContextAllocationForParameters() {
force_context_allocation_for_parameters_ = true;
bool has_forced_context_allocation_for_parameters() const {
return force_context_allocation_for_parameters_;
// ---------------------------------------------------------------------------
// Predicates.
// Specific scope types.
bool is_eval_scope() const { return scope_type_ == EVAL_SCOPE; }
bool is_function_scope() const { return scope_type_ == FUNCTION_SCOPE; }
bool is_module_scope() const { return scope_type_ == MODULE_SCOPE; }
bool is_script_scope() const { return scope_type_ == SCRIPT_SCOPE; }
bool is_catch_scope() const { return scope_type_ == CATCH_SCOPE; }
bool is_block_scope() const { return scope_type_ == BLOCK_SCOPE; }
bool is_with_scope() const { return scope_type_ == WITH_SCOPE; }
bool is_declaration_scope() const { return is_declaration_scope_; }
bool inner_scope_calls_eval() const { return inner_scope_calls_eval_; }
bool IsAsmModule() const;
// Returns true if this scope or any inner scopes that might be eagerly
// compiled are asm modules.
bool ContainsAsmModule() const;
// Does this scope have the potential to execute declarations non-linearly?
bool is_nonlinear() const { return scope_nonlinear_; }
// Whether this needs to be represented by a runtime context.
bool NeedsContext() const {
// Catch scopes always have heap slots.
DCHECK(!is_catch_scope() || num_heap_slots() > 0);
return num_heap_slots() > 0;
// ---------------------------------------------------------------------------
// Accessors.
// The type of this scope.
ScopeType scope_type() const { return scope_type_; }
// The language mode of this scope.
LanguageMode language_mode() const {
return is_strict_ ? LanguageMode::kStrict : LanguageMode::kSloppy;
// inner_scope() and sibling() together implement the inner scope list of a
// scope. Inner scope points to the an inner scope of the function, and
// "sibling" points to a next inner scope of the outer scope of this scope.
Scope* inner_scope() const { return inner_scope_; }
Scope* sibling() const { return sibling_; }
// The scope immediately surrounding this scope, or nullptr.
Scope* outer_scope() const { return outer_scope_; }
Variable* catch_variable() const {
DCHECK_EQ(1, num_var());
return static_cast<Variable*>(variables_.Start()->value);
bool ShouldBanArguments();
// ---------------------------------------------------------------------------
// Variable allocation.
// Result of variable allocation.
int num_stack_slots() const { return num_stack_slots_; }
int num_heap_slots() const { return num_heap_slots_; }
int StackLocalCount() const;
int ContextLocalCount() const;
// Determine if we can parse a function literal in this scope lazily without
// caring about the unresolved variables within.
bool AllowsLazyParsingWithoutUnresolvedVariables(const Scope* outer) const;
// The number of contexts between this and scope; zero if this == scope.
int ContextChainLength(Scope* scope) const;
// The number of contexts between this and the outermost context that has a
// sloppy eval call. One if this->calls_sloppy_eval().
int ContextChainLengthUntilOutermostSloppyEval() const;
// Find the first function, script, eval or (declaration) block scope. This is
// the scope where var declarations will be hoisted to in the implementation.
DeclarationScope* GetDeclarationScope();
// Find the first non-block declaration scope. This should be either a script,
// function, or eval scope. Same as DeclarationScope(), but skips declaration
// "block" scopes. Used for differentiating associated function objects (i.e.,
// the scope for which a function prologue allocates a context) or declaring
// temporaries.
DeclarationScope* GetClosureScope();
const DeclarationScope* GetClosureScope() const;
// Find the first (non-arrow) function or script scope. This is where
// 'this' is bound, and what determines the function kind.
DeclarationScope* GetReceiverScope();
// Find the innermost outer scope that needs a context.
Scope* GetOuterScopeWithContext();
// Analyze() must have been called once to create the ScopeInfo.
Handle<ScopeInfo> scope_info() const {
return scope_info_;
int num_var() const { return variables_.occupancy(); }
// ---------------------------------------------------------------------------
// Debugging.
#ifdef DEBUG
void Print(int n = 0); // n = indentation; n < 0 => don't print recursively
// Check that the scope has positions assigned.
void CheckScopePositions();
// Check that all Scopes in the scope tree use the same Zone.
void CheckZones();
// Retrieve `IsSimpleParameterList` of current or outer function.
bool HasSimpleParameters();
void set_is_debug_evaluate_scope() { is_debug_evaluate_scope_ = true; }
bool is_debug_evaluate_scope() const { return is_debug_evaluate_scope_; }
bool RemoveInnerScope(Scope* inner_scope) {
if (inner_scope == inner_scope_) {
inner_scope_ = inner_scope_->sibling_;
return true;
for (Scope* scope = inner_scope_; scope != nullptr;
scope = scope->sibling_) {
if (scope->sibling_ == inner_scope) {
scope->sibling_ = scope->sibling_->sibling_;
return true;
return false;
explicit Scope(Zone* zone);
void set_language_mode(LanguageMode language_mode) {
is_strict_ = is_strict(language_mode);
Variable* Declare(
Zone* zone, const AstRawString* name, VariableMode mode,
VariableKind kind = NORMAL_VARIABLE,
InitializationFlag initialization_flag = kCreatedInitialized,
MaybeAssignedFlag maybe_assigned_flag = kNotAssigned);
// This method should only be invoked on scopes created during parsing (i.e.,
// not deserialized from a context). Also, since NeedsContext() is only
// returning a valid result after variables are resolved, NeedsScopeInfo()
// should also be invoked after resolution.
bool NeedsScopeInfo() const;
Variable* NewTemporary(const AstRawString* name,
MaybeAssignedFlag maybe_assigned);
// Walk the scope chain to find DeclarationScopes; call
// SavePreParsedScopeDataForDeclarationScope for each.
void SavePreParsedScopeData();
Zone* zone_;
// Scope tree.
Scope* outer_scope_; // the immediately enclosing outer scope, or nullptr
Scope* inner_scope_; // an inner scope of this scope
Scope* sibling_; // a sibling inner scope of the outer scope of this scope.
// The variables declared in this scope:
// All user-declared variables (incl. parameters). For script scopes
// variables may be implicitly 'declared' by being used (possibly in
// an inner scope) with no intervening with statements or eval calls.
VariableMap variables_;
// In case of non-scopeinfo-backed scopes, this contains the variables of the
// map above in order of addition.
ThreadedList<Variable> locals_;
// Unresolved variables referred to from this scope. The proxies themselves
// form a linked list of all unresolved proxies.
VariableProxy* unresolved_;
// Declarations.
ThreadedList<Declaration> decls_;
// Serialized scope info support.
Handle<ScopeInfo> scope_info_;
// Debugging support.
#ifdef DEBUG
const AstRawString* scope_name_;
// True if it doesn't need scope resolution (e.g., if the scope was
// constructed based on a serialized scope info or a catch context).
bool already_resolved_;
// True if this scope may contain objects from a temp zone that needs to be
// fixed up.
bool needs_migration_;
// Source positions.
int start_position_;
int end_position_;
// Computed via AllocateVariables.
int num_stack_slots_;
int num_heap_slots_;
// The scope type.
const ScopeType scope_type_;
// Scope-specific information computed during parsing.
// The language mode of this scope.
STATIC_ASSERT(LanguageModeSize == 2);
bool is_strict_ : 1;
// This scope or a nested catch scope or with scope contain an 'eval' call. At
// the 'eval' call site this scope is the declaration scope.
bool scope_calls_eval_ : 1;
// This scope's declarations might not be executed in order (e.g., switch).
bool scope_nonlinear_ : 1;
bool is_hidden_ : 1;
// Temporary workaround that allows masking of 'this' in debug-evalute scopes.
bool is_debug_evaluate_scope_ : 1;
// True if one of the inner scopes or the scope itself calls eval.
bool inner_scope_calls_eval_ : 1;
bool force_context_allocation_ : 1;
bool force_context_allocation_for_parameters_ : 1;
// True if it holds 'var' declarations.
bool is_declaration_scope_ : 1;
bool must_use_preparsed_scope_data_ : 1;
// Create a non-local variable with a given name.
// These variables are looked up dynamically at runtime.
Variable* NonLocal(const AstRawString* name, VariableMode mode);
// Variable resolution.
// Lookup a variable reference given by name recursively starting with this
// scope, and stopping when reaching the outer_scope_end scope. If the code is
// executed because of a call to 'eval', the context parameter should be set
// to the calling context of 'eval'.
Variable* LookupRecursive(VariableProxy* proxy, Scope* outer_scope_end);
void ResolveTo(ParseInfo* info, VariableProxy* proxy, Variable* var);
void ResolveVariable(ParseInfo* info, VariableProxy* proxy);
void ResolveVariablesRecursively(ParseInfo* info);
// Finds free variables of this scope. This mutates the unresolved variables
// list along the way, so full resolution cannot be done afterwards.
// If a ParseInfo* is passed, non-free variables will be resolved.
VariableProxy* FetchFreeVariables(DeclarationScope* max_outer_scope,
ParseInfo* info = nullptr,
VariableProxy* stack = nullptr);
// Predicates.
bool MustAllocate(Variable* var);
bool MustAllocateInContext(Variable* var);
// Variable allocation.
void AllocateStackSlot(Variable* var);
void AllocateHeapSlot(Variable* var);
void AllocateNonParameterLocal(Variable* var);
void AllocateDeclaredGlobal(Variable* var);
void AllocateNonParameterLocalsAndDeclaredGlobals();
void AllocateVariablesRecursively();
void AllocateScopeInfosRecursively(Isolate* isolate,
MaybeHandle<ScopeInfo> outer_scope);
void AllocateDebuggerScopeInfos(Isolate* isolate,
MaybeHandle<ScopeInfo> outer_scope);
// Construct a scope based on the scope info.
Scope(Zone* zone, ScopeType type, Handle<ScopeInfo> scope_info);
// Construct a catch scope with a binding for the name.
Scope(Zone* zone, const AstRawString* catch_variable_name,
MaybeAssignedFlag maybe_assigned, Handle<ScopeInfo> scope_info);
void AddInnerScope(Scope* inner_scope) {
inner_scope->sibling_ = inner_scope_;
inner_scope_ = inner_scope;
inner_scope->outer_scope_ = this;
void SetDefaults();
friend class DeclarationScope;
friend class ScopeTestHelper;
class V8_EXPORT_PRIVATE DeclarationScope : public Scope {
DeclarationScope(Zone* zone, Scope* outer_scope, ScopeType scope_type,
FunctionKind function_kind = kNormalFunction);
DeclarationScope(Zone* zone, ScopeType scope_type,
Handle<ScopeInfo> scope_info);
// Creates a script scope.
DeclarationScope(Zone* zone, AstValueFactory* ast_value_factory);
bool IsDeclaredParameter(const AstRawString* name) {
// If IsSimpleParameterList is false, duplicate parameters are not allowed,
// however `arguments` may be allowed if function is not strict code. Thus,
// the assumptions explained above do not hold.
return params_.Contains(variables_.Lookup(name));
FunctionKind function_kind() const { return function_kind_; }
bool is_arrow_scope() const {
return is_function_scope() && IsArrowFunction(function_kind_);
// Inform the scope that the corresponding code uses "super".
void RecordSuperPropertyUsage() {
DCHECK(IsConciseMethod(function_kind()) ||
IsAccessorFunction(function_kind()) ||
scope_uses_super_property_ = true;
// Does this scope access "super" property (
bool NeedsHomeObject() const {
return scope_uses_super_property_ ||
(inner_scope_calls_eval_ && (IsConciseMethod(function_kind()) ||
IsAccessorFunction(function_kind()) ||
bool calls_sloppy_eval() const {
return scope_calls_eval_ && is_sloppy(language_mode());
bool was_lazily_parsed() const { return was_lazily_parsed_; }
#ifdef DEBUG
void set_is_being_lazily_parsed(bool is_being_lazily_parsed) {
is_being_lazily_parsed_ = is_being_lazily_parsed;
bool is_being_lazily_parsed() const { return is_being_lazily_parsed_; }
bool ShouldEagerCompile() const;
void set_should_eager_compile();
void SetScriptScopeInfo(Handle<ScopeInfo> scope_info) {
scope_info_ = scope_info;
bool asm_module() const { return asm_module_; }
void set_asm_module();
bool should_ban_arguments() const {
return IsClassFieldsInitializerFunction(function_kind());
void DeclareThis(AstValueFactory* ast_value_factory);
void DeclareArguments(AstValueFactory* ast_value_factory);
void DeclareDefaultFunctionVariables(AstValueFactory* ast_value_factory);
// Declare the function variable for a function literal. This variable
// is in an intermediate scope between this function scope and the the
// outer scope. Only possible for function scopes; at most one variable.
// This function needs to be called after all other variables have been
// declared in the scope. It will add a variable for {name} to {variables_};
// either the function variable itself, or a non-local in case the function
// calls sloppy eval.
Variable* DeclareFunctionVar(const AstRawString* name);
// Declare some special internal variables which must be accessible to
// Ignition without ScopeInfo.
Variable* DeclareGeneratorObjectVar(const AstRawString* name);
Variable* DeclarePromiseVar(const AstRawString* name);
// Declare a parameter in this scope. When there are duplicated
// parameters the rightmost one 'wins'. However, the implementation
// expects all parameters to be declared and from left to right.
Variable* DeclareParameter(const AstRawString* name, VariableMode mode,
bool is_optional, bool is_rest, bool* is_duplicate,
AstValueFactory* ast_value_factory, int position);
// Declares that a parameter with the name exists. Creates a Variable and
// returns it if FLAG_preparser_scope_analysis is on.
Variable* DeclareParameterName(const AstRawString* name, bool is_rest,
AstValueFactory* ast_value_factory,
bool declare_local, bool add_parameter);
// Declare an implicit global variable in this scope which must be a
// script scope. The variable was introduced (possibly from an inner
// scope) by a reference to an unresolved variable with no intervening
// with statements or eval calls.
Variable* DeclareDynamicGlobal(const AstRawString* name,
VariableKind variable_kind);
// The variable corresponding to the 'this' value.
Variable* receiver() {
return receiver_;
// TODO(wingo): Add a GLOBAL_SCOPE scope type which will lexically allocate
// "this" (and no other variable) on the native context. Script scopes then
// will not have a "this" declaration.
bool has_this_declaration() const {
return (is_function_scope() && !is_arrow_scope()) || is_module_scope();
// The variable corresponding to the '' value.
Variable* new_target_var() { return new_target_; }
// The variable holding the function literal for named function
// literals, or nullptr. Only valid for function scopes.
Variable* function_var() const { return function_; }
Variable* generator_object_var() const {
DCHECK(is_function_scope() || is_module_scope());
return GetRareVariable(RareVariable::kGeneratorObject);
Variable* promise_var() const {
if (IsAsyncGeneratorFunction(function_kind_)) return nullptr;
return GetRareVariable(RareVariable::kPromise);
// Parameters. The left-most parameter has index 0.
// Only valid for function and module scopes.
Variable* parameter(int index) const {
DCHECK(is_function_scope() || is_module_scope());
return params_[index];
// Returns the number of formal parameters, excluding a possible rest
// parameter. Examples:
// function foo(a, b) {} ==> 2
// function foo(a, b, ...c) {} ==> 2
// function foo(a, b, c = 1) {} ==> 3
int num_parameters() const {
return has_rest_ ? params_.length() - 1 : params_.length();
// The function's rest parameter (nullptr if there is none).
Variable* rest_parameter() const {
return has_rest_ ? params_[params_.length() - 1] : nullptr;
bool has_simple_parameters() const { return has_simple_parameters_; }
// TODO(caitp): manage this state in a better way. PreParser must be able to
// communicate that the scope is non-simple, without allocating any parameters
// as the Parser does. This is necessary to ensure that TC39's proposed early
// error can be reported consistently regardless of whether lazily parsed or
// not.
void SetHasNonSimpleParameters() {
has_simple_parameters_ = false;
// The local variable 'arguments' if we need to allocate it; nullptr
// otherwise.
Variable* arguments() const {
DCHECK(!is_arrow_scope() || arguments_ == nullptr);
return arguments_;
Variable* this_function_var() const {
Variable* this_function = GetRareVariable(RareVariable::kThisFunction);
// This is only used in derived constructors atm.
DCHECK(this_function == nullptr ||
(is_function_scope() && (IsClassConstructor(function_kind()) ||
IsConciseMethod(function_kind()) ||
return this_function;
// Adds a local variable in this scope's locals list. This is for adjusting
// the scope of temporaries and do-expression vars when desugaring parameter
// initializers.
void AddLocal(Variable* var);
void DeclareSloppyBlockFunction(
const AstRawString* name, Scope* scope,
SloppyBlockFunctionStatement* statement = nullptr);
// Go through sloppy_block_function_map_ and hoist those (into this scope)
// which should be hoisted.
void HoistSloppyBlockFunctions(AstNodeFactory* factory);
SloppyBlockFunctionMap* sloppy_block_function_map() {
return sloppy_block_function_map_;
// Replaces the outer scope with the outer_scope_info in |info| if there is
// one.
void AttachOuterScopeInfo(ParseInfo* info, Isolate* isolate);
// Compute top scope and allocate variables. For lazy compilation the top
// scope only contains the single lazily compiled function, so this
// doesn't re-allocate variables repeatedly.
static void Analyze(ParseInfo* info);
// To be called during parsing. Do just enough scope analysis that we can
// discard the Scope contents for lazily compiled functions. In particular,
// this records variables which cannot be resolved inside the Scope (we don't
// yet know what they will resolve to since the outer Scopes are incomplete)
// and recreates them with the correct Zone with ast_node_factory.
void AnalyzePartially(AstNodeFactory* ast_node_factory);
// Allocate ScopeInfos for top scope and any inner scopes that need them.
// Does nothing if ScopeInfo is already allocated.
static void AllocateScopeInfos(ParseInfo* info, Isolate* isolate,
AnalyzeMode mode);
Handle<StringSet> CollectNonLocals(ParseInfo* info,
Handle<StringSet> non_locals);
// Determine if we can use lazy compilation for this scope.
bool AllowsLazyCompilation() const;
// Make sure this closure and all outer closures are eagerly compiled.
void ForceEagerCompilation() {
DCHECK_EQ(this, GetClosureScope());
DeclarationScope* s;
for (s = this; !s->is_script_scope();
s = s->outer_scope()->GetClosureScope()) {
s->force_eager_compilation_ = true;
s->force_eager_compilation_ = true;
#ifdef DEBUG
void PrintParameters();
void AllocateLocals();
void AllocateParameterLocals();
void AllocateReceiver();
void ResetAfterPreparsing(AstValueFactory* ast_value_factory, bool aborted);
bool is_skipped_function() const { return is_skipped_function_; }
void set_is_skipped_function(bool is_skipped_function) {
is_skipped_function_ = is_skipped_function;
// Save data describing the context allocation of the variables in this scope
// and its subscopes (except scopes at the laziness boundary). The data is
// saved in produced_preparsed_scope_data_.
void SavePreParsedScopeDataForDeclarationScope();
void set_produced_preparsed_scope_data(
ProducedPreParsedScopeData* produced_preparsed_scope_data) {
produced_preparsed_scope_data_ = produced_preparsed_scope_data;
ProducedPreParsedScopeData* produced_preparsed_scope_data() const {
return produced_preparsed_scope_data_;
void AllocateParameter(Variable* var, int index);
// Resolve and fill in the allocation information for all variables
// in this scopes. Must be called *after* all scopes have been
// processed (parsed) to ensure that unresolved variables can be
// resolved properly.
// In the case of code compiled and run using 'eval', the context
// parameter is the context in which eval was called. In all other
// cases the context parameter is an empty handle.
void AllocateVariables(ParseInfo* info);
void SetDefaults();
// If the scope is a function scope, this is the function kind.
const FunctionKind function_kind_;
bool has_simple_parameters_ : 1;
// This scope contains an "use asm" annotation.
bool asm_module_ : 1;
bool force_eager_compilation_ : 1;
// This function scope has a rest parameter.
bool has_rest_ : 1;
// This scope has a parameter called "arguments".
bool has_arguments_parameter_ : 1;
// This scope uses "super" property ('').
bool scope_uses_super_property_ : 1;
bool should_eager_compile_ : 1;
// Set to true after we have finished lazy parsing the scope.
bool was_lazily_parsed_ : 1;
bool is_being_lazily_parsed_ : 1;
bool is_skipped_function_ : 1;
// Parameter list in source order.
ZoneList<Variable*> params_;
// Map of function names to lists of functions defined in sloppy blocks
SloppyBlockFunctionMap* sloppy_block_function_map_;
// Convenience variable.
Variable* receiver_;
// Function variable, if any; function scopes only.
Variable* function_;
// variable, function scopes only.
Variable* new_target_;
// Convenience variable; function scopes only.
Variable* arguments_;
// For producing the scope allocation data during preparsing.
ProducedPreParsedScopeData* produced_preparsed_scope_data_;
struct RareData : public ZoneObject {
// Convenience variable; Subclass constructor only
Variable* this_function = nullptr;
// Generator object, if any; generator function scopes and module scopes
// only.
Variable* generator_object = nullptr;
// Promise, if any; async function scopes only.
Variable* promise = nullptr;
enum class RareVariable {
kThisFunction = offsetof(RareData, this_function),
kGeneratorObject = offsetof(RareData, generator_object),
kPromise = offsetof(RareData, promise)
V8_INLINE RareData* EnsureRareData() {
if (rare_data_ == nullptr) {
rare_data_ = new (zone_) RareData;
return rare_data_;
V8_INLINE Variable* GetRareVariable(RareVariable id) const {
if (rare_data_ == nullptr) return nullptr;
return *reinterpret_cast<Variable**>(
reinterpret_cast<uint8_t*>(rare_data_) + static_cast<ptrdiff_t>(id));
// Set `var` to null if it's non-null and Predicate (Variable*) -> bool
// returns true.
template <typename Predicate>
V8_INLINE void NullifyRareVariableIf(RareVariable id, Predicate predicate) {
if (V8_LIKELY(rare_data_ == nullptr)) return;
Variable** var = reinterpret_cast<Variable**>(
reinterpret_cast<uint8_t*>(rare_data_) + static_cast<ptrdiff_t>(id));
if (*var && predicate(*var)) *var = nullptr;
RareData* rare_data_ = nullptr;
class ModuleScope final : public DeclarationScope {
ModuleScope(DeclarationScope* script_scope,
AstValueFactory* ast_value_factory);
// Deserialization.
// The generated ModuleDescriptor does not preserve all information. In
// particular, its module_requests map will be empty because we no longer need
// the map after parsing.
ModuleScope(Handle<ScopeInfo> scope_info, AstValueFactory* ast_value_factory);
ModuleDescriptor* module() const {
return module_descriptor_;
// Set MODULE as VariableLocation for all variables that will live in a
// module's export table.
void AllocateModuleVariables();
ModuleDescriptor* module_descriptor_;
} // namespace internal
} // namespace v8
#endif // V8_AST_SCOPES_H_