Imported QtWebKit TP3 (git b57bc6801f1876c3220d5a4bfea33d620d477443)

Change-Id: I3b1d8a2808782c9f34d50240000e20cb38d3680f
Reviewed-by: Konstantin Tokarev <annulen@yandex.ru>

1 files changed, 901 insertions, 421 deletions

diff --git a/Source/JavaScriptCore/parser/Parser.h b/Source/JavaScriptCore/parser/Parser.h
index 87d523404..02a726a56 100644
--- a/Source/JavaScriptCore/parser/Parser.h
+++ b/Source/JavaScriptCore/parser/Parser.h
@@ -31,14 +31,14 @@
 #include "Nodes.h"
 #include "ParserArena.h"
 #include "ParserError.h"
+#include "ParserFunctionInfo.h"
 #include "ParserTokens.h"
 #include "SourceProvider.h"
 #include "SourceProviderCache.h"
 #include "SourceProviderCacheItem.h"
-#include "VMStackBounds.h"
+#include "VariableEnvironment.h"
 #include <wtf/Forward.h>
 #include <wtf/Noncopyable.h>
-#include <wtf/OwnPtr.h>
 #include <wtf/RefPtr.h>
 namespace JSC {
 struct Scope;
@@ -53,7 +53,7 @@ template <> struct VectorTraits<JSC::Scope> : SimpleClassVectorTraits {
 namespace JSC {
 
 class ExecState;
-class FunctionBodyNode;
+class FunctionMetadataNode;
 class FunctionParameters;
 class Identifier;
 class VM;
@@ -67,60 +67,116 @@ class SourceCode;
 #define TreeSourceElements typename TreeBuilder::SourceElements
 #define TreeClause typename TreeBuilder::Clause
 #define TreeClauseList typename TreeBuilder::ClauseList
-#define TreeConstDeclList typename TreeBuilder::ConstDeclList
 #define TreeArguments typename TreeBuilder::Arguments
 #define TreeArgumentsList typename TreeBuilder::ArgumentsList
 #define TreeFunctionBody typename TreeBuilder::FunctionBody
+#define TreeClassExpression typename TreeBuilder::ClassExpression
 #define TreeProperty typename TreeBuilder::Property
 #define TreePropertyList typename TreeBuilder::PropertyList
+#define TreeDestructuringPattern typename TreeBuilder::DestructuringPattern
 
 COMPILE_ASSERT(LastUntaggedToken < 64, LessThan64UntaggedTokens);
 
 enum SourceElementsMode { CheckForStrictMode, DontCheckForStrictMode };
+enum FunctionBodyType { ArrowFunctionBodyExpression, ArrowFunctionBodyBlock, StandardFunctionBodyBlock };
 enum FunctionRequirements { FunctionNoRequirements, FunctionNeedsName };
 
+enum class DestructuringKind {
+    DestructureToVariables,
+    DestructureToLet,
+    DestructureToConst,
+    DestructureToCatchParameters,
+    DestructureToParameters,
+    DestructureToExpressions
+};
+
+enum class DeclarationType { 
+    VarDeclaration, 
+    LetDeclaration,
+    ConstDeclaration
+};
+
+enum class DeclarationImportType {
+    Imported,
+    ImportedNamespace,
+    NotImported
+};
+
+enum DeclarationResult {
+    Valid = 0,
+    InvalidStrictMode = 1 << 0,
+    InvalidDuplicateDeclaration = 1 << 1
+};
+
+typedef uint8_t DeclarationResultMask;
+
+
 template <typename T> inline bool isEvalNode() { return false; }
 template <> inline bool isEvalNode<EvalNode>() { return true; }
 
-struct DepthManager {
-    DepthManager(int* depth)
-        : m_originalDepth(*depth)
-        , m_depth(depth)
-    {
-    }
+struct ScopeLabelInfo {
+    UniquedStringImpl* uid;
+    bool isLoop;
+};
+
+ALWAYS_INLINE static bool isArguments(const VM* vm, const Identifier* ident)
+{
+    return vm->propertyNames->arguments == *ident;
+}
+ALWAYS_INLINE static bool isEval(const VM* vm, const Identifier* ident)
+{
+    return vm->propertyNames->eval == *ident;
+}
+ALWAYS_INLINE static bool isEvalOrArgumentsIdentifier(const VM* vm, const Identifier* ident)
+{
+    return isEval(vm, ident) || isArguments(vm, ident);
+}
+ALWAYS_INLINE static bool isIdentifierOrKeyword(const JSToken& token)
+{
+    return token.m_type == IDENT || token.m_type & KeywordTokenFlag;
+}
+
+class ModuleScopeData : public RefCounted<ModuleScopeData> {
+public:
+    static Ref<ModuleScopeData> create() { return adoptRef(*new ModuleScopeData); }
+
+    const IdentifierSet& exportedBindings() const { return m_exportedBindings; }
 
-    ~DepthManager()
+    bool exportName(const Identifier& exportedName)
     {
-        *m_depth = m_originalDepth;
+        return m_exportedNames.add(exportedName.impl()).isNewEntry;
     }
 
-private:
-    int m_originalDepth;
-    int* m_depth;
-};
-
-struct ScopeLabelInfo {
-    ScopeLabelInfo(StringImpl* ident, bool isLoop)
-        : m_ident(ident)
-        , m_isLoop(isLoop)
+    void exportBinding(const Identifier& localName)
     {
+        m_exportedBindings.add(localName.impl());
     }
 
-    StringImpl* m_ident;
-    bool m_isLoop;
+private:
+    IdentifierSet m_exportedNames { };
+    IdentifierSet m_exportedBindings { };
 };
 
 struct Scope {
-    Scope(const VM* vm, bool isFunction, bool strictMode)
+    Scope(const VM* vm, bool isFunction, bool isGenerator, bool strictMode)
         : m_vm(vm)
         , m_shadowsArguments(false)
         , m_usesEval(false)
         , m_needsFullActivation(false)
-        , m_allowsNewDecls(true)
+        , m_hasDirectSuper(false)
+        , m_needsSuperBinding(false)
+        , m_allowsVarDeclarations(true)
+        , m_allowsLexicalDeclarations(true)
         , m_strictMode(strictMode)
         , m_isFunction(isFunction)
+        , m_isGenerator(isGenerator)
+        , m_isArrowFunction(false)
+        , m_isLexicalScope(false)
         , m_isFunctionBoundary(false)
         , m_isValidStrictMode(true)
+        , m_hasArguments(false)
+        , m_constructorKind(static_cast<unsigned>(ConstructorKind::None))
+        , m_expectedSuperBinding(static_cast<unsigned>(SuperBinding::NotNeeded))
         , m_loopDepth(0)
         , m_switchDepth(0)
     {
@@ -131,21 +187,31 @@ struct Scope {
         , m_shadowsArguments(rhs.m_shadowsArguments)
         , m_usesEval(rhs.m_usesEval)
         , m_needsFullActivation(rhs.m_needsFullActivation)
-        , m_allowsNewDecls(rhs.m_allowsNewDecls)
+        , m_hasDirectSuper(rhs.m_hasDirectSuper)
+        , m_needsSuperBinding(rhs.m_needsSuperBinding)
+        , m_allowsVarDeclarations(rhs.m_allowsVarDeclarations)
+        , m_allowsLexicalDeclarations(rhs.m_allowsLexicalDeclarations)
         , m_strictMode(rhs.m_strictMode)
         , m_isFunction(rhs.m_isFunction)
+        , m_isGenerator(rhs.m_isGenerator)
+        , m_isArrowFunction(rhs.m_isArrowFunction)
+        , m_isLexicalScope(rhs.m_isLexicalScope)
         , m_isFunctionBoundary(rhs.m_isFunctionBoundary)
         , m_isValidStrictMode(rhs.m_isValidStrictMode)
+        , m_hasArguments(rhs.m_hasArguments)
+        , m_constructorKind(rhs.m_constructorKind)
+        , m_expectedSuperBinding(rhs.m_expectedSuperBinding)
         , m_loopDepth(rhs.m_loopDepth)
         , m_switchDepth(rhs.m_switchDepth)
+        , m_moduleScopeData(rhs.m_moduleScopeData)
     {
         if (rhs.m_labels) {
-            m_labels = adoptPtr(new LabelStack);
+            m_labels = std::make_unique<LabelStack>();
 
             typedef LabelStack::const_iterator iterator;
             iterator end = rhs.m_labels->end();
             for (iterator it = rhs.m_labels->begin(); it != end; ++it)
-                m_labels->append(ScopeLabelInfo(it->m_ident, it->m_isLoop));
+                m_labels->append(ScopeLabelInfo { it->uid, it->isLoop });
         }
     }
 
@@ -160,8 +226,8 @@ struct Scope {
     void pushLabel(const Identifier* label, bool isLoop)
     {
         if (!m_labels)
-            m_labels = adoptPtr(new LabelStack);
-        m_labels->append(ScopeLabelInfo(label->impl(), isLoop));
+            m_labels = std::make_unique<LabelStack>();
+        m_labels->append(ScopeLabelInfo { label->impl(), isLoop });
     }
 
     void popLabel()
@@ -176,115 +242,321 @@ struct Scope {
         if (!m_labels)
             return 0;
         for (int i = m_labels->size(); i > 0; i--) {
-            if (m_labels->at(i - 1).m_ident == label->impl())
+            if (m_labels->at(i - 1).uid == label->impl())
                 return &m_labels->at(i - 1);
         }
         return 0;
     }
 
-    void setIsFunction()
+    void setSourceParseMode(SourceParseMode mode)
     {
-        m_isFunction = true;
-        m_isFunctionBoundary = true;
+        switch (mode) {
+        case SourceParseMode::GeneratorBodyMode:
+            setIsGenerator();
+            break;
+
+        case SourceParseMode::GeneratorWrapperFunctionMode:
+            setIsGeneratorFunction();
+            break;
+
+        case SourceParseMode::NormalFunctionMode:
+        case SourceParseMode::GetterMode:
+        case SourceParseMode::SetterMode:
+        case SourceParseMode::MethodMode:
+            setIsFunction();
+            break;
+
+        case SourceParseMode::ArrowFunctionMode:
+            setIsArrowFunction();
+            break;
+
+        case SourceParseMode::ProgramMode:
+            break;
+
+        case SourceParseMode::ModuleAnalyzeMode:
+        case SourceParseMode::ModuleEvaluateMode:
+            setIsModule();
+            break;
+        }
+    }
+
+    bool isFunction() const { return m_isFunction; }
+    bool isFunctionBoundary() const { return m_isFunctionBoundary; }
+    bool isGenerator() const { return m_isGenerator; }
+
+    bool hasArguments() const { return m_hasArguments; }
+
+    void setIsLexicalScope() 
+    { 
+        m_isLexicalScope = true;
+        m_allowsLexicalDeclarations = true;
+    }
+    bool isLexicalScope() { return m_isLexicalScope; }
+
+    const IdentifierSet& closedVariableCandidates() const { return m_closedVariableCandidates; }
+    VariableEnvironment& declaredVariables() { return m_declaredVariables; }
+    VariableEnvironment& lexicalVariables() { return m_lexicalVariables; }
+    VariableEnvironment& finalizeLexicalEnvironment() 
+    { 
+        if (m_usesEval || m_needsFullActivation)
+            m_lexicalVariables.markAllVariablesAsCaptured();
+        else
+            computeLexicallyCapturedVariablesAndPurgeCandidates();
+
+        return m_lexicalVariables;
     }
-    bool isFunction() { return m_isFunction; }
-    bool isFunctionBoundary() { return m_isFunctionBoundary; }
 
-    void declareCallee(const Identifier* ident)
+    ModuleScopeData& moduleScopeData() const
     {
-        m_declaredVariables.add(ident->string().impl());
+        ASSERT(m_moduleScopeData);
+        return *m_moduleScopeData;
     }
 
-    bool declareVariable(const Identifier* ident)
+    void computeLexicallyCapturedVariablesAndPurgeCandidates()
     {
-        bool isValidStrictMode = m_vm->propertyNames->eval != *ident && m_vm->propertyNames->arguments != *ident;
+        // Because variables may be defined at any time in the range of a lexical scope, we must
+        // track lexical variables that might be captured. Then, when we're preparing to pop the top
+        // lexical scope off the stack, we should find which variables are truly captured, and which
+        // variable still may be captured in a parent scope.
+        if (m_lexicalVariables.size() && m_closedVariableCandidates.size()) {
+            auto end = m_closedVariableCandidates.end();
+            for (auto iter = m_closedVariableCandidates.begin(); iter != end; ++iter)
+                m_lexicalVariables.markVariableAsCapturedIfDefined(iter->get());
+        }
+
+        // We can now purge values from the captured candidates because they're captured in this scope.
+        {
+            for (auto entry : m_lexicalVariables) {
+                if (entry.value.isCaptured())
+                    m_closedVariableCandidates.remove(entry.key);
+            }
+        }
+    }
+
+    DeclarationResultMask declareCallee(const Identifier* ident)
+    {
+        auto addResult = m_declaredVariables.add(ident->impl());
+        // We want to track if callee is captured, but we don't want to act like it's a 'var'
+        // because that would cause the BytecodeGenerator to emit bad code.
+        addResult.iterator->value.clearIsVar();
+
+        DeclarationResultMask result = DeclarationResult::Valid;
+        if (isEvalOrArgumentsIdentifier(m_vm, ident))
+            result |= DeclarationResult::InvalidStrictMode;
+        return result;
+    }
+
+    DeclarationResultMask declareVariable(const Identifier* ident)
+    {
+        ASSERT(m_allowsVarDeclarations);
+        DeclarationResultMask result = DeclarationResult::Valid;
+        bool isValidStrictMode = !isEvalOrArgumentsIdentifier(m_vm, ident);
         m_isValidStrictMode = m_isValidStrictMode && isValidStrictMode;
-        m_declaredVariables.add(ident->string().impl());
-        return isValidStrictMode;
+        auto addResult = m_declaredVariables.add(ident->impl());
+        addResult.iterator->value.setIsVar();
+        if (!isValidStrictMode)
+            result |= DeclarationResult::InvalidStrictMode;
+        if (m_lexicalVariables.contains(ident->impl()))
+            result |= DeclarationResult::InvalidDuplicateDeclaration;
+        return result;
     }
 
+    DeclarationResultMask declareLexicalVariable(const Identifier* ident, bool isConstant, DeclarationImportType importType = DeclarationImportType::NotImported)
+    {
+        ASSERT(m_allowsLexicalDeclarations);
+        DeclarationResultMask result = DeclarationResult::Valid;
+        bool isValidStrictMode = !isEvalOrArgumentsIdentifier(m_vm, ident);
+        m_isValidStrictMode = m_isValidStrictMode && isValidStrictMode;
+        auto addResult = m_lexicalVariables.add(ident->impl());
+        if (isConstant)
+            addResult.iterator->value.setIsConst();
+        else
+            addResult.iterator->value.setIsLet();
+
+        if (importType == DeclarationImportType::Imported)
+            addResult.iterator->value.setIsImported();
+        else if (importType == DeclarationImportType::ImportedNamespace) {
+            addResult.iterator->value.setIsImported();
+            addResult.iterator->value.setIsImportedNamespace();
+        }
+
+        if (!addResult.isNewEntry)
+            result |= DeclarationResult::InvalidDuplicateDeclaration;
+        if (!isValidStrictMode)
+            result |= DeclarationResult::InvalidStrictMode;
+
+        return result;
+    }
+
+    bool hasDeclaredVariable(const Identifier& ident)
+    {
+        return hasDeclaredVariable(ident.impl());
+    }
+
+    bool hasDeclaredVariable(const RefPtr<UniquedStringImpl>& ident)
+    {
+        auto iter = m_declaredVariables.find(ident.get());
+        if (iter == m_declaredVariables.end())
+            return false;
+        VariableEnvironmentEntry entry = iter->value;
+        return entry.isVar(); // The callee isn't a "var".
+    }
+
+    bool hasLexicallyDeclaredVariable(const RefPtr<UniquedStringImpl>& ident) const
+    {
+        return m_lexicalVariables.contains(ident.get());
+    }
+    
+    ALWAYS_INLINE bool hasDeclaredParameter(const Identifier& ident)
+    {
+        return hasDeclaredParameter(ident.impl());
+    }
+
+    bool hasDeclaredParameter(const RefPtr<UniquedStringImpl>& ident)
+    {
+        return m_declaredParameters.contains(ident) || hasDeclaredVariable(ident);
+    }
+    
     void declareWrite(const Identifier* ident)
     {
         ASSERT(m_strictMode);
         m_writtenVariables.add(ident->impl());
     }
 
-    void preventNewDecls() { m_allowsNewDecls = false; }
-    bool allowsNewDecls() const { return m_allowsNewDecls; }
+    void preventAllVariableDeclarations()
+    {
+        m_allowsVarDeclarations = false; 
+        m_allowsLexicalDeclarations = false;
+    }
+    void preventVarDeclarations() { m_allowsVarDeclarations = false; }
+    bool allowsVarDeclarations() const { return m_allowsVarDeclarations; }
+    bool allowsLexicalDeclarations() const { return m_allowsLexicalDeclarations; }
 
-    bool declareParameter(const Identifier* ident)
+    DeclarationResultMask declareParameter(const Identifier* ident)
     {
-        bool isArguments = m_vm->propertyNames->arguments == *ident;
-        bool isValidStrictMode = m_declaredVariables.add(ident->string().impl()).isNewEntry && m_vm->propertyNames->eval != *ident && !isArguments;
+        ASSERT(m_allowsVarDeclarations);
+        DeclarationResultMask result = DeclarationResult::Valid;
+        bool isArgumentsIdent = isArguments(m_vm, ident);
+        auto addResult = m_declaredVariables.add(ident->impl());
+        addResult.iterator->value.clearIsVar();
+        bool isValidStrictMode = addResult.isNewEntry && m_vm->propertyNames->eval != *ident && !isArgumentsIdent;
         m_isValidStrictMode = m_isValidStrictMode && isValidStrictMode;
-        if (isArguments)
+        m_declaredParameters.add(ident->impl());
+        if (!isValidStrictMode)
+            result |= DeclarationResult::InvalidStrictMode;
+        if (isArgumentsIdent)
             m_shadowsArguments = true;
-        return isValidStrictMode;
+        if (!addResult.isNewEntry)
+            result |= DeclarationResult::InvalidDuplicateDeclaration;
+
+        return result;
+    }
+    
+    void getUsedVariables(IdentifierSet& usedVariables)
+    {
+        usedVariables.swap(m_usedVariables);
     }
 
     void useVariable(const Identifier* ident, bool isEval)
     {
         m_usesEval |= isEval;
-        m_usedVariables.add(ident->string().impl());
+        m_usedVariables.add(ident->impl());
     }
 
     void setNeedsFullActivation() { m_needsFullActivation = true; }
+    bool needsFullActivation() const { return m_needsFullActivation; }
+    bool isArrowFunction() { return m_isArrowFunction; }
+
+    bool hasDirectSuper() { return m_hasDirectSuper; }
+    void setHasDirectSuper() { m_hasDirectSuper = true; }
 
-    bool collectFreeVariables(Scope* nestedScope, bool shouldTrackClosedVariables)
+    bool needsSuperBinding() { return m_needsSuperBinding; }
+    void setNeedsSuperBinding() { m_needsSuperBinding = true; }
+    
+    void setExpectedSuperBinding(SuperBinding superBinding) { m_expectedSuperBinding = static_cast<unsigned>(superBinding); }
+    SuperBinding expectedSuperBinding() const { return static_cast<SuperBinding>(m_expectedSuperBinding); }
+    void setConstructorKind(ConstructorKind constructorKind) { m_constructorKind = static_cast<unsigned>(constructorKind); }
+    ConstructorKind constructorKind() const { return static_cast<ConstructorKind>(m_constructorKind); }
+
+    void collectFreeVariables(Scope* nestedScope, bool shouldTrackClosedVariables)
     {
         if (nestedScope->m_usesEval)
             m_usesEval = true;
-        IdentifierSet::iterator end = nestedScope->m_usedVariables.end();
-        for (IdentifierSet::iterator ptr = nestedScope->m_usedVariables.begin(); ptr != end; ++ptr) {
-            if (nestedScope->m_declaredVariables.contains(*ptr))
-                continue;
-            m_usedVariables.add(*ptr);
-            if (shouldTrackClosedVariables)
-                m_closedVariables.add(*ptr);
+
+        {
+            for (const RefPtr<UniquedStringImpl>& impl : nestedScope->m_usedVariables) {
+                if (nestedScope->m_declaredVariables.contains(impl) || nestedScope->m_lexicalVariables.contains(impl))
+                    continue;
+
+                // "arguments" reference should be resolved at function boudary.
+                if (nestedScope->isFunctionBoundary() && nestedScope->hasArguments() && impl == m_vm->propertyNames->arguments.impl() && !nestedScope->isArrowFunction())
+                    continue;
+
+                m_usedVariables.add(impl);
+                // We don't want a declared variable that is used in an inner scope to be thought of as captured if
+                // that inner scope is both a lexical scope and not a function. Only inner functions and "catch" 
+                // statements can cause variables to be captured.
+                if (shouldTrackClosedVariables && (nestedScope->m_isFunctionBoundary || !nestedScope->m_isLexicalScope))
+                    m_closedVariableCandidates.add(impl);
+            }
+        }
+        // Propagate closed variable candidates downwards within the same function.
+        // Cross function captures will be realized via m_usedVariables propagation.
+        if (shouldTrackClosedVariables && !nestedScope->m_isFunctionBoundary && nestedScope->m_closedVariableCandidates.size()) {
+            IdentifierSet::iterator end = nestedScope->m_closedVariableCandidates.end();
+            IdentifierSet::iterator begin = nestedScope->m_closedVariableCandidates.begin();
+            m_closedVariableCandidates.add(begin, end);
         }
+
         if (nestedScope->m_writtenVariables.size()) {
             IdentifierSet::iterator end = nestedScope->m_writtenVariables.end();
             for (IdentifierSet::iterator ptr = nestedScope->m_writtenVariables.begin(); ptr != end; ++ptr) {
-                if (nestedScope->m_declaredVariables.contains(*ptr))
+                if (nestedScope->m_declaredVariables.contains(*ptr) || nestedScope->m_lexicalVariables.contains(*ptr))
                     continue;
                 m_writtenVariables.add(*ptr);
             }
         }
-
-        return true;
-    }
-
-    void getUncapturedWrittenVariables(IdentifierSet& writtenVariables)
-    {
-        IdentifierSet::iterator end = m_writtenVariables.end();
-        for (IdentifierSet::iterator ptr = m_writtenVariables.begin(); ptr != end; ++ptr) {
-            if (!m_declaredVariables.contains(*ptr))
-                writtenVariables.add(*ptr);
-        }
     }
-
-    void getCapturedVariables(IdentifierSet& capturedVariables)
+    
+    void getCapturedVars(IdentifierSet& capturedVariables, bool& modifiedParameter, bool& modifiedArguments)
     {
         if (m_needsFullActivation || m_usesEval) {
-            capturedVariables.swap(m_declaredVariables);
+            modifiedParameter = true;
+            for (auto& entry : m_declaredVariables)
+                capturedVariables.add(entry.key);
             return;
         }
-        for (IdentifierSet::iterator ptr = m_closedVariables.begin(); ptr != m_closedVariables.end(); ++ptr) {
-            if (!m_declaredVariables.contains(*ptr))
+        for (IdentifierSet::iterator ptr = m_closedVariableCandidates.begin(); ptr != m_closedVariableCandidates.end(); ++ptr) {
+            // We refer to m_declaredVariables here directly instead of a hasDeclaredVariable because we want to mark the callee as captured.
+            if (!m_declaredVariables.contains(*ptr)) 
                 continue;
             capturedVariables.add(*ptr);
         }
+        modifiedParameter = false;
+        if (shadowsArguments())
+            modifiedArguments = true;
+        if (m_declaredParameters.size()) {
+            IdentifierSet::iterator end = m_writtenVariables.end();
+            for (IdentifierSet::iterator ptr = m_writtenVariables.begin(); ptr != end; ++ptr) {
+                if (*ptr == m_vm->propertyNames->arguments.impl())
+                    modifiedArguments = true;
+                if (!m_declaredParameters.contains(*ptr))
+                    continue;
+                modifiedParameter = true;
+                break;
+            }
+        }
     }
     void setStrictMode() { m_strictMode = true; }
     bool strictMode() const { return m_strictMode; }
     bool isValidStrictMode() const { return m_isValidStrictMode; }
     bool shadowsArguments() const { return m_shadowsArguments; }
 
-    void copyCapturedVariablesToVector(const IdentifierSet& capturedVariables, Vector<RefPtr<StringImpl> >& vector)
+    void copyCapturedVariablesToVector(const IdentifierSet& capturedVariables, Vector<RefPtr<UniquedStringImpl>>& vector)
     {
         IdentifierSet::iterator end = capturedVariables.end();
         for (IdentifierSet::iterator it = capturedVariables.begin(); it != end; ++it) {
-            if (m_declaredVariables.contains(*it))
+            if (m_declaredVariables.contains(*it) || m_lexicalVariables.contains(*it))
                 continue;
             vector.append(*it);
         }
@@ -313,24 +585,69 @@ struct Scope {
     }
 
 private:
+    void setIsFunction()
+    {
+        m_isFunction = true;
+        m_isFunctionBoundary = true;
+        m_hasArguments = true;
+        setIsLexicalScope();
+        m_isGenerator = false;
+    }
+
+    void setIsGeneratorFunction()
+    {
+        setIsFunction();
+        m_isGenerator = true;
+    }
+
+    void setIsGenerator()
+    {
+        setIsFunction();
+        m_isGenerator = true;
+        m_hasArguments = false;
+    }
+    
+    void setIsArrowFunction()
+    {
+        setIsFunction();
+        m_isArrowFunction = true;
+    }
+
+    void setIsModule()
+    {
+        m_moduleScopeData = ModuleScopeData::create();
+    }
+
     const VM* m_vm;
     bool m_shadowsArguments : 1;
     bool m_usesEval : 1;
     bool m_needsFullActivation : 1;
-    bool m_allowsNewDecls : 1;
+    bool m_hasDirectSuper : 1;
+    bool m_needsSuperBinding : 1;
+    bool m_allowsVarDeclarations : 1;
+    bool m_allowsLexicalDeclarations : 1;
     bool m_strictMode : 1;
     bool m_isFunction : 1;
+    bool m_isGenerator : 1;
+    bool m_isArrowFunction : 1;
+    bool m_isLexicalScope : 1;
     bool m_isFunctionBoundary : 1;
     bool m_isValidStrictMode : 1;
+    bool m_hasArguments : 1;
+    unsigned m_constructorKind : 2;
+    unsigned m_expectedSuperBinding : 2;
     int m_loopDepth;
     int m_switchDepth;
 
     typedef Vector<ScopeLabelInfo, 2> LabelStack;
-    OwnPtr<LabelStack> m_labels;
-    IdentifierSet m_declaredVariables;
+    std::unique_ptr<LabelStack> m_labels;
+    IdentifierSet m_declaredParameters;
+    VariableEnvironment m_declaredVariables;
+    VariableEnvironment m_lexicalVariables;
     IdentifierSet m_usedVariables;
-    IdentifierSet m_closedVariables;
+    IdentifierSet m_closedVariableCandidates;
     IdentifierSet m_writtenVariables;
+    RefPtr<ModuleScopeData> m_moduleScopeData { };
 };
 
 typedef Vector<Scope, 10> ScopeStack;
@@ -360,17 +677,27 @@ private:
     unsigned m_index;
 };
 
+enum class ArgumentType {
+    Normal,
+    Spread
+};
+
 template <typename LexerType>
 class Parser {
     WTF_MAKE_NONCOPYABLE(Parser);
     WTF_MAKE_FAST_ALLOCATED;
 
 public:
-    Parser(VM*, const SourceCode&, FunctionParameters*, const Identifier&, JSParserStrictness, JSParserMode);
+    Parser(
+        VM*, const SourceCode&, JSParserBuiltinMode, JSParserStrictMode, SourceParseMode, SuperBinding,
+        ConstructorKind defaultConstructorKind = ConstructorKind::None, ThisTDZMode = ThisTDZMode::CheckIfNeeded);
     ~Parser();
 
     template <class ParsedNode>
-    PassRefPtr<ParsedNode> parse(ParserError&);
+    std::unique_ptr<ParsedNode> parse(ParserError&, const Identifier&, SourceParseMode);
+
+    JSTextPosition positionBeforeLastNewline() const { return m_lexer->positionBeforeLastNewline(); }
+    JSTokenLocation locationBeforeLastToken() const { return m_lexer->lastTokenLocation(); }
 
 private:
     struct AllowInOverride {
@@ -410,60 +737,269 @@ private:
         Parser* m_parser;
     };
 
+    struct AutoCleanupLexicalScope {
+        // We can allocate this object on the stack without actually knowing beforehand if we're 
+        // going to create a new lexical scope. If we decide to create a new lexical scope, we
+        // can pass the scope into this obejct and it will take care of the cleanup for us if the parse fails.
+        // This is helpful if we may fail from syntax errors after creating a lexical scope conditionally.
+        AutoCleanupLexicalScope()
+            : m_scope(nullptr, UINT_MAX)
+            , m_parser(nullptr)
+        {
+        }
+
+        ~AutoCleanupLexicalScope()
+        {
+            // This should only ever be called if we fail from a syntax error. Otherwise
+            // it's the intention that a user of this class pops this scope manually on a 
+            // successful parse. 
+            if (isValid())
+                m_parser->popScope(*this, false);
+        }
+
+        void setIsValid(ScopeRef& scope, Parser* parser)
+        {
+            RELEASE_ASSERT(scope->isLexicalScope());
+            m_scope = scope;
+            m_parser = parser;
+        }
+
+        bool isValid() const { return !!m_parser; }
+
+        void setPopped()
+        {
+            m_parser = nullptr;
+        }
+
+        ScopeRef& scope() { return m_scope; }
+
+    private:
+        ScopeRef m_scope;
+        Parser* m_parser;
+    };
+
+    enum ExpressionErrorClass {
+        ErrorIndicatesNothing,
+        ErrorIndicatesPattern
+    };
+
+    struct ExpressionErrorClassifier {
+        ExpressionErrorClassifier(Parser* parser)
+            : m_class(ErrorIndicatesNothing)
+            , m_previous(parser->m_expressionErrorClassifier)
+            , m_parser(parser)
+        {
+            m_parser->m_expressionErrorClassifier = this;
+        }
+
+        ~ExpressionErrorClassifier()
+        {
+            m_parser->m_expressionErrorClassifier = m_previous;
+        }
+
+        void classifyExpressionError(ExpressionErrorClass classification)
+        {
+            if (m_class != ErrorIndicatesNothing)
+                return;
+            m_class = classification;
+        }
+
+        void reclassifyExpressionError(ExpressionErrorClass oldClassification, ExpressionErrorClass classification)
+        {
+            if (m_class != oldClassification)
+                return;
+            m_class = classification;
+        }
+
+        void propagateExpressionErrorClass()
+        {
+            if (m_previous && m_class != ErrorIndicatesNothing)
+                m_previous->m_class = m_class;
+        }
+
+        bool indicatesPossiblePattern() const { return m_class == ErrorIndicatesPattern; }
+
+    private:
+        ExpressionErrorClass m_class;
+        ExpressionErrorClassifier* m_previous;
+        Parser* m_parser;
+    };
+
+    ALWAYS_INLINE void classifyExpressionError(ExpressionErrorClass classification)
+    {
+        if (m_expressionErrorClassifier)
+            m_expressionErrorClassifier->classifyExpressionError(classification);
+    }
+
+    ALWAYS_INLINE void reclassifyExpressionError(ExpressionErrorClass oldClassification, ExpressionErrorClass classification)
+    {
+        if (m_expressionErrorClassifier)
+            m_expressionErrorClassifier->reclassifyExpressionError(oldClassification, classification);
+    }
+
+    ALWAYS_INLINE DestructuringKind destructuringKindFromDeclarationType(DeclarationType type)
+    {
+        switch (type) {
+        case DeclarationType::VarDeclaration:
+            return DestructuringKind::DestructureToVariables;
+        case DeclarationType::LetDeclaration:
+            return DestructuringKind::DestructureToLet;
+        case DeclarationType::ConstDeclaration:
+            return DestructuringKind::DestructureToConst;
+        }
+
+        RELEASE_ASSERT_NOT_REACHED();
+        return DestructuringKind::DestructureToVariables;
+    }
+
+    ALWAYS_INLINE AssignmentContext assignmentContextFromDeclarationType(DeclarationType type)
+    {
+        switch (type) {
+        case DeclarationType::ConstDeclaration:
+            return AssignmentContext::ConstDeclarationStatement;
+        default:
+            return AssignmentContext::DeclarationStatement;
+        }
+    }
+
+    ALWAYS_INLINE bool isEvalOrArguments(const Identifier* ident) { return isEvalOrArgumentsIdentifier(m_vm, ident); }
+
     ScopeRef currentScope()
     {
         return ScopeRef(&m_scopeStack, m_scopeStack.size() - 1);
     }
+
+    ScopeRef currentVariableScope()
+    {
+        unsigned i = m_scopeStack.size() - 1;
+        ASSERT(i < m_scopeStack.size());
+        while (!m_scopeStack[i].allowsVarDeclarations()) {
+            i--;
+            ASSERT(i < m_scopeStack.size());
+        }
+        return ScopeRef(&m_scopeStack, i);
+    }
+
+    ScopeRef currentFunctionScope()
+    {
+        unsigned i = m_scopeStack.size() - 1;
+        ASSERT(i < m_scopeStack.size());
+        while (i && !m_scopeStack[i].isFunctionBoundary()) {
+            i--;
+            ASSERT(i < m_scopeStack.size());
+        }
+        // When reaching the top level scope (it can be non function scope), we return it.
+        return ScopeRef(&m_scopeStack, i);
+    }
+
+    ScopeRef closestParentNonArrowFunctionNonLexicalScope()
+    {
+        unsigned i = m_scopeStack.size() - 1;
+        ASSERT(i < m_scopeStack.size() && m_scopeStack.size());
+        while (i && (!m_scopeStack[i].isFunctionBoundary() || m_scopeStack[i].isArrowFunction()))
+            i--;
+        // When reaching the top level scope (it can be non function scope), we return it.
+        return ScopeRef(&m_scopeStack, i);
+    }
     
     ScopeRef pushScope()
     {
         bool isFunction = false;
         bool isStrict = false;
+        bool isGenerator = false;
         if (!m_scopeStack.isEmpty()) {
             isStrict = m_scopeStack.last().strictMode();
             isFunction = m_scopeStack.last().isFunction();
+            isGenerator = m_scopeStack.last().isGenerator();
         }
-        m_scopeStack.append(Scope(m_vm, isFunction, isStrict));
+        m_scopeStack.append(Scope(m_vm, isFunction, isGenerator, isStrict));
         return currentScope();
     }
     
-    bool popScopeInternal(ScopeRef& scope, bool shouldTrackClosedVariables)
+    void popScopeInternal(ScopeRef& scope, bool shouldTrackClosedVariables)
     {
         ASSERT_UNUSED(scope, scope.index() == m_scopeStack.size() - 1);
         ASSERT(m_scopeStack.size() > 1);
-        bool result = m_scopeStack[m_scopeStack.size() - 2].collectFreeVariables(&m_scopeStack.last(), shouldTrackClosedVariables);
+        m_scopeStack[m_scopeStack.size() - 2].collectFreeVariables(&m_scopeStack.last(), shouldTrackClosedVariables);
+        if (!m_scopeStack.last().isFunctionBoundary() && m_scopeStack.last().needsFullActivation())
+            m_scopeStack[m_scopeStack.size() - 2].setNeedsFullActivation();
         m_scopeStack.removeLast();
-        return result;
     }
     
-    bool popScope(ScopeRef& scope, bool shouldTrackClosedVariables)
+    ALWAYS_INLINE void popScope(ScopeRef& scope, bool shouldTrackClosedVariables)
     {
-        return popScopeInternal(scope, shouldTrackClosedVariables);
+        popScopeInternal(scope, shouldTrackClosedVariables);
     }
     
-    bool popScope(AutoPopScopeRef& scope, bool shouldTrackClosedVariables)
+    ALWAYS_INLINE void popScope(AutoPopScopeRef& scope, bool shouldTrackClosedVariables)
     {
         scope.setPopped();
-        return popScopeInternal(scope, shouldTrackClosedVariables);
+        popScopeInternal(scope, shouldTrackClosedVariables);
+    }
+
+    ALWAYS_INLINE void popScope(AutoCleanupLexicalScope& cleanupScope, bool shouldTrackClosedVariables)
+    {
+        RELEASE_ASSERT(cleanupScope.isValid());
+        ScopeRef& scope = cleanupScope.scope();
+        cleanupScope.setPopped();
+        popScopeInternal(scope, shouldTrackClosedVariables);
     }
     
-    bool declareVariable(const Identifier* ident)
+    DeclarationResultMask declareVariable(const Identifier* ident, DeclarationType type = DeclarationType::VarDeclaration, DeclarationImportType importType = DeclarationImportType::NotImported)
     {
+        if (type == DeclarationType::VarDeclaration)
+            return currentVariableScope()->declareVariable(ident);
+
         unsigned i = m_scopeStack.size() - 1;
         ASSERT(i < m_scopeStack.size());
-        while (!m_scopeStack[i].allowsNewDecls()) {
+        ASSERT(type == DeclarationType::LetDeclaration || type == DeclarationType::ConstDeclaration);
+
+        // Lexical variables declared at a top level scope that shadow arguments or vars are not allowed.
+        if (m_statementDepth == 1 && (hasDeclaredParameter(*ident) || hasDeclaredVariable(*ident)))
+            return DeclarationResult::InvalidDuplicateDeclaration;
+
+        while (!m_scopeStack[i].allowsLexicalDeclarations()) {
             i--;
             ASSERT(i < m_scopeStack.size());
         }
-        return m_scopeStack[i].declareVariable(ident);
+
+        return m_scopeStack[i].declareLexicalVariable(ident, type == DeclarationType::ConstDeclaration, importType);
+    }
+    
+    NEVER_INLINE bool hasDeclaredVariable(const Identifier& ident)
+    {
+        unsigned i = m_scopeStack.size() - 1;
+        ASSERT(i < m_scopeStack.size());
+        while (!m_scopeStack[i].allowsVarDeclarations()) {
+            i--;
+            ASSERT(i < m_scopeStack.size());
+        }
+        return m_scopeStack[i].hasDeclaredVariable(ident);
+    }
+
+    NEVER_INLINE bool hasDeclaredParameter(const Identifier& ident)
+    {
+        unsigned i = m_scopeStack.size() - 1;
+        ASSERT(i < m_scopeStack.size());
+        while (!m_scopeStack[i].allowsVarDeclarations()) {
+            i--;
+            ASSERT(i < m_scopeStack.size());
+        }
+        return m_scopeStack[i].hasDeclaredParameter(ident);
     }
     
     void declareWrite(const Identifier* ident)
     {
-        if (!m_syntaxAlreadyValidated)
+        if (!m_syntaxAlreadyValidated || strictMode())
             m_scopeStack.last().declareWrite(ident);
     }
-    
+
+    bool exportName(const Identifier& ident)
+    {
+        ASSERT(currentScope().index() == 0);
+        return currentScope()->moduleScopeData().exportName(ident);
+    }
+
     ScopeStack m_scopeStack;
     
     const SourceProviderCacheItem* findCachedFunctionInfo(int openBracePos) 
@@ -472,14 +1008,13 @@ private:
     }
 
     Parser();
-    String parseInner();
+    String parseInner(const Identifier&, SourceParseMode);
 
-    void didFinishParsing(SourceElements*, ParserArenaData<DeclarationStacks::VarStack>*, 
-        ParserArenaData<DeclarationStacks::FunctionStack>*, CodeFeatures, int, IdentifierSet&);
+    void didFinishParsing(SourceElements*, DeclarationStacks::FunctionStack&, VariableEnvironment&, CodeFeatures, int);
 
     // Used to determine type of error to report.
-    bool isFunctionBodyNode(ScopeNode*) { return false; }
-    bool isFunctionBodyNode(FunctionBodyNode*) { return true; }
+    bool isFunctionMetadataNode(ScopeNode*) { return false; }
+    bool isFunctionMetadataNode(FunctionMetadataNode*) { return true; }
 
     ALWAYS_INLINE void next(unsigned lexerFlags = 0)
     {
@@ -489,6 +1024,8 @@ private:
         m_lastTokenEndPosition = JSTextPosition(lastLine, lastTokenEnd, lastTokenLineStart);
         m_lexer->setLastLineNumber(lastLine);
         m_token.m_type = m_lexer->lex(&m_token, lexerFlags, strictMode());
+        if (UNLIKELY(m_token.m_type == CONSTTOKEN && m_vm->shouldRewriteConstAsVar()))
+            m_token.m_type = VAR;
     }
 
     ALWAYS_INLINE void nextExpectIdentifier(unsigned lexerFlags = 0)
@@ -513,8 +1050,9 @@ private:
             next(flags);
         return result;
     }
-    
-    ALWAYS_INLINE String getToken() {
+
+    void printUnexpectedTokenText(WTF::PrintStream&);
+    ALWAYS_INLINE StringView getToken() {
         SourceProvider* sourceProvider = m_source->provider();
         return sourceProvider->getRange(tokenStart(), tokenEndPosition().offset);
     }
@@ -524,6 +1062,21 @@ private:
         return m_token.m_type == expected;
     }
     
+    ALWAYS_INLINE bool matchContextualKeyword(const Identifier& identifier)
+    {
+        return m_token.m_type == IDENT && *m_token.m_data.ident == identifier;
+    }
+
+    ALWAYS_INLINE bool matchIdentifierOrKeyword()
+    {
+        return isIdentifierOrKeyword(m_token);
+    }
+    
+    ALWAYS_INLINE bool isEndOfArrowFunction()
+    {
+        return match(SEMICOLON) || match(COMMA) || match(CLOSEPAREN) || match(CLOSEBRACE) || match(CLOSEBRACKET) || match(EOFTOK) || m_lexer->prevTerminator();
+    }
+
     ALWAYS_INLINE unsigned tokenStart()
     {
         return m_token.m_location.startOffset;
@@ -559,281 +1112,23 @@ private:
         return m_token.m_location;
     }
 
-    const char* getTokenName(JSTokenType tok)
-    {
-        switch (tok) {
-        case NULLTOKEN: 
-            return "null";
-        case TRUETOKEN:
-            return "true";
-        case FALSETOKEN: 
-            return "false";
-        case BREAK: 
-            return "break";
-        case CASE: 
-            return "case";
-        case DEFAULT: 
-            return "default";
-        case FOR: 
-            return "for";
-        case NEW: 
-            return "new";
-        case VAR: 
-            return "var";
-        case CONSTTOKEN: 
-            return "const";
-        case CONTINUE: 
-            return "continue";
-        case FUNCTION: 
-            return "function";
-        case IF: 
-            return "if";
-        case THISTOKEN: 
-            return "this";
-        case DO: 
-            return "do";
-        case WHILE: 
-            return "while";
-        case SWITCH: 
-            return "switch";
-        case WITH: 
-            return "with";
-        case THROW: 
-            return "throw";
-        case TRY: 
-            return "try";
-        case CATCH: 
-            return "catch";
-        case FINALLY: 
-            return "finally";
-        case DEBUGGER: 
-            return "debugger";
-        case ELSE: 
-            return "else";
-        case OPENBRACE: 
-            return "{";
-        case CLOSEBRACE: 
-            return "}";
-        case OPENPAREN: 
-            return "(";
-        case CLOSEPAREN: 
-            return ")";
-        case OPENBRACKET: 
-            return "[";
-        case CLOSEBRACKET: 
-            return "]";
-        case COMMA: 
-            return ",";
-        case QUESTION: 
-            return "?";
-        case SEMICOLON: 
-            return ";";
-        case COLON: 
-            return ":";
-        case DOT: 
-            return ".";
-        case EQUAL: 
-            return "=";
-        case PLUSEQUAL: 
-            return "+=";
-        case MINUSEQUAL: 
-            return "-=";
-        case MULTEQUAL: 
-            return "*=";
-        case DIVEQUAL: 
-            return "/=";
-        case LSHIFTEQUAL: 
-            return "<<=";
-        case RSHIFTEQUAL: 
-            return ">>=";
-        case URSHIFTEQUAL: 
-            return ">>>=";
-        case ANDEQUAL: 
-            return "&=";
-        case MODEQUAL: 
-            return "%=";
-        case XOREQUAL: 
-            return "^=";
-        case OREQUAL: 
-            return "|=";
-        case AUTOPLUSPLUS: 
-        case PLUSPLUS: 
-            return "++";
-        case AUTOMINUSMINUS: 
-        case MINUSMINUS: 
-            return "--";
-        case EXCLAMATION: 
-            return "!";
-        case TILDE: 
-            return "~";
-        case TYPEOF: 
-            return "typeof";
-        case VOIDTOKEN: 
-            return "void";
-        case DELETETOKEN: 
-            return "delete";
-        case OR: 
-            return "||";
-        case AND: 
-            return "&&";
-        case BITOR: 
-            return "|";
-        case BITXOR: 
-            return "^";
-        case BITAND: 
-            return "&";
-        case EQEQ: 
-            return "==";
-        case NE: 
-            return "!=";
-        case STREQ: 
-            return "===";
-        case STRNEQ: 
-            return "!==";
-        case LT: 
-            return "<";
-        case GT: 
-            return ">";
-        case LE: 
-            return "<=";
-        case GE: 
-            return ">=";
-        case INSTANCEOF: 
-            return "instanceof";
-        case INTOKEN: 
-            return "in";
-        case LSHIFT: 
-            return "<<";
-        case RSHIFT: 
-            return ">>";
-        case URSHIFT: 
-            return ">>>";
-        case PLUS: 
-            return "+";
-        case MINUS: 
-            return "-";
-        case TIMES: 
-            return "*";
-        case DIVIDE: 
-            return "/";
-        case MOD: 
-            return "%";
-        case RETURN: 
-        case RESERVED_IF_STRICT:
-        case RESERVED: 
-        case NUMBER:
-        case IDENT: 
-        case STRING:
-        case UNTERMINATED_IDENTIFIER_ESCAPE_ERRORTOK:
-        case UNTERMINATED_IDENTIFIER_UNICODE_ESCAPE_ERRORTOK:
-        case UNTERMINATED_MULTILINE_COMMENT_ERRORTOK:
-        case UNTERMINATED_NUMERIC_LITERAL_ERRORTOK:
-        case UNTERMINATED_STRING_LITERAL_ERRORTOK:
-        case INVALID_IDENTIFIER_ESCAPE_ERRORTOK:
-        case INVALID_IDENTIFIER_UNICODE_ESCAPE_ERRORTOK:
-        case INVALID_NUMERIC_LITERAL_ERRORTOK:
-        case INVALID_OCTAL_NUMBER_ERRORTOK:
-        case INVALID_STRING_LITERAL_ERRORTOK:
-        case ERRORTOK:
-        case EOFTOK:
-            return 0;
-        case LastUntaggedToken: 
-            break;
-        }
-        RELEASE_ASSERT_NOT_REACHED();
-        return "internal error";
-    }
-    
-    ALWAYS_INLINE void updateErrorMessageSpecialCase(JSTokenType expectedToken) 
-    {
-        switch (expectedToken) {
-        case RESERVED_IF_STRICT:
-            m_errorMessage = "Use of reserved word '" + getToken() + "' in strict mode";
-            return;
-        case RESERVED:
-            m_errorMessage = "Use of reserved word '" + getToken() + '\'';
-            return;
-        case NUMBER: 
-            m_errorMessage = "Unexpected number '" + getToken() + '\'';
-            return;
-        case IDENT: 
-            m_errorMessage = "Expected an identifier but found '" + getToken() + "' instead";
-            return;
-        case STRING: 
-            m_errorMessage = "Unexpected string " + getToken();
-            return;
-            
-        case UNTERMINATED_IDENTIFIER_ESCAPE_ERRORTOK:
-        case UNTERMINATED_IDENTIFIER_UNICODE_ESCAPE_ERRORTOK:
-            m_errorMessage = "Incomplete unicode escape in identifier: '" + getToken() + '\'';
-            return;
-        case UNTERMINATED_MULTILINE_COMMENT_ERRORTOK:
-            m_errorMessage = "Unterminated multiline comment";
-            return;
-        case UNTERMINATED_NUMERIC_LITERAL_ERRORTOK:
-            m_errorMessage = "Unterminated numeric literal '" + getToken() + '\'';
-            return;
-        case UNTERMINATED_STRING_LITERAL_ERRORTOK:
-            m_errorMessage = "Unterminated string literal '" + getToken() + '\'';
-            return;
-        case INVALID_IDENTIFIER_ESCAPE_ERRORTOK:
-            m_errorMessage = "Invalid escape in identifier: '" + getToken() + '\'';
-            return;
-        case INVALID_IDENTIFIER_UNICODE_ESCAPE_ERRORTOK:
-            m_errorMessage = "Invalid unicode escape in identifier: '" + getToken() + '\'';
-            return;
-        case INVALID_NUMERIC_LITERAL_ERRORTOK:
-            m_errorMessage = "Invalid numeric literal: '" + getToken() + '\'';
-            return;
-        case INVALID_OCTAL_NUMBER_ERRORTOK:
-            m_errorMessage = "Invalid use of octal: '" + getToken() + '\'';
-                return;
-        case INVALID_STRING_LITERAL_ERRORTOK:
-            m_errorMessage = "Invalid string literal: '" + getToken() + '\'';
-            return;
-        case ERRORTOK:
-            m_errorMessage = "Unrecognized token '" + getToken() + '\'';
-            return;
-        case EOFTOK:  
-            m_errorMessage = ASCIILiteral("Unexpected EOF");
-            return;
-        case RETURN:
-            m_errorMessage = ASCIILiteral("Return statements are only valid inside functions");
-            return;
-        default:
-            RELEASE_ASSERT_NOT_REACHED();
-            m_errorMessage = ASCIILiteral("internal error");
-            return;
-        }
-    }
-    
-    NEVER_INLINE void updateErrorMessage() 
+    void setErrorMessage(const String& message)
     {
-        const char* name = getTokenName(m_token.m_type);
-        if (!name) 
-            updateErrorMessageSpecialCase(m_token.m_type);
-        else 
-            m_errorMessage = String::format("Unexpected token '%s'", name);
-        ASSERT(!m_errorMessage.isNull());
+        m_errorMessage = message;
     }
     
-    NEVER_INLINE void updateErrorMessage(JSTokenType expectedToken) 
-    {
-        const char* name = getTokenName(expectedToken);
-        if (name)
-            m_errorMessage = String::format("Expected token '%s'", name);
-        else {
-            if (!getTokenName(m_token.m_type))
-                updateErrorMessageSpecialCase(m_token.m_type);
-            else
-                updateErrorMessageSpecialCase(expectedToken);
-        }
-        ASSERT(!m_errorMessage.isNull());
-    }
+    NEVER_INLINE void logError(bool);
+    template <typename A> NEVER_INLINE void logError(bool, const A&);
+    template <typename A, typename B> NEVER_INLINE void logError(bool, const A&, const B&);
+    template <typename A, typename B, typename C> NEVER_INLINE void logError(bool, const A&, const B&, const C&);
+    template <typename A, typename B, typename C, typename D> NEVER_INLINE void logError(bool, const A&, const B&, const C&, const D&);
+    template <typename A, typename B, typename C, typename D, typename E> NEVER_INLINE void logError(bool, const A&, const B&, const C&, const D&, const E&);
+    template <typename A, typename B, typename C, typename D, typename E, typename F> NEVER_INLINE void logError(bool, const A&, const B&, const C&, const D&, const E&, const F&);
+    template <typename A, typename B, typename C, typename D, typename E, typename F, typename G> NEVER_INLINE void logError(bool, const A&, const B&, const C&, const D&, const E&, const F&, const G&);
     
-    NEVER_INLINE void updateErrorWithNameAndMessage(const char* beforeMsg, String name, const char* afterMsg)
+    NEVER_INLINE void updateErrorWithNameAndMessage(const char* beforeMessage, const String& name, const char* afterMessage)
     {
-        m_errorMessage = makeString(beforeMsg, " '", name, "' ", afterMsg);
+        m_errorMessage = makeString(beforeMessage, " '", name, "' ", afterMessage);
     }
     
     NEVER_INLINE void updateErrorMessage(const char* msg)
@@ -850,7 +1145,9 @@ private:
     void setStrictMode() { currentScope()->setStrictMode(); }
     bool strictMode() { return currentScope()->strictMode(); }
     bool isValidStrictMode() { return currentScope()->isValidStrictMode(); }
-    bool declareParameter(const Identifier* ident) { return currentScope()->declareParameter(ident); }
+    DeclarationResultMask declareParameter(const Identifier* ident) { return currentScope()->declareParameter(ident); }
+    bool declareRestOrNormalParameter(const Identifier&, const Identifier**);
+
     bool breakIsValid()
     {
         ScopeRef current = currentScope();
@@ -872,7 +1169,7 @@ private:
         return true;
     }
     void pushLabel(const Identifier* label, bool isLoop) { currentScope()->pushLabel(label, isLoop); }
-    void popLabel() { currentScope()->popLabel(); }
+    void popLabel(ScopeRef scope) { scope->popLabel(); }
     ScopeLabelInfo* getLabel(const Identifier* label)
     {
         ScopeRef current = currentScope();
@@ -884,12 +1181,38 @@ private:
         }
         return result;
     }
-    
-    template <SourceElementsMode mode, class TreeBuilder> TreeSourceElements parseSourceElements(TreeBuilder&);
+
+    // http://ecma-international.org/ecma-262/6.0/#sec-identifiers-static-semantics-early-errors
+    ALWAYS_INLINE bool isLETMaskedAsIDENT()
+    {
+        return match(LET) && !strictMode();
+    }
+
+    // http://ecma-international.org/ecma-262/6.0/#sec-identifiers-static-semantics-early-errors
+    ALWAYS_INLINE bool isYIELDMaskedAsIDENT(bool inGenerator)
+    {
+        return match(YIELD) && !strictMode() && !inGenerator;
+    }
+
+    // http://ecma-international.org/ecma-262/6.0/#sec-generator-function-definitions-static-semantics-early-errors
+    ALWAYS_INLINE bool matchSpecIdentifier(bool inGenerator)
+    {
+        return match(IDENT) || isLETMaskedAsIDENT() || isYIELDMaskedAsIDENT(inGenerator);
+    }
+
+    ALWAYS_INLINE bool matchSpecIdentifier()
+    {
+        return matchSpecIdentifier(currentScope()->isGenerator());
+    }
+
+    template <class TreeBuilder> TreeSourceElements parseSourceElements(TreeBuilder&, SourceElementsMode);
+    template <class TreeBuilder> TreeSourceElements parseGeneratorFunctionSourceElements(TreeBuilder&, SourceElementsMode);
+    template <class TreeBuilder> TreeStatement parseStatementListItem(TreeBuilder&, const Identifier*& directive, unsigned* directiveLiteralLength);
     template <class TreeBuilder> TreeStatement parseStatement(TreeBuilder&, const Identifier*& directive, unsigned* directiveLiteralLength = 0);
-    template <class TreeBuilder> TreeStatement parseFunctionDeclaration(TreeBuilder&);
-    template <class TreeBuilder> TreeStatement parseVarDeclaration(TreeBuilder&);
-    template <class TreeBuilder> TreeStatement parseConstDeclaration(TreeBuilder&);
+    enum class ExportType { Exported, NotExported };
+    template <class TreeBuilder> TreeStatement parseClassDeclaration(TreeBuilder&, ExportType = ExportType::NotExported);
+    template <class TreeBuilder> TreeStatement parseFunctionDeclaration(TreeBuilder&, ExportType = ExportType::NotExported);
+    template <class TreeBuilder> TreeStatement parseVariableDeclaration(TreeBuilder&, DeclarationType, ExportType = ExportType::NotExported);
     template <class TreeBuilder> TreeStatement parseDoWhileStatement(TreeBuilder&);
     template <class TreeBuilder> TreeStatement parseWhileStatement(TreeBuilder&);
     template <class TreeBuilder> TreeStatement parseForStatement(TreeBuilder&);
@@ -906,9 +1229,12 @@ private:
     template <class TreeBuilder> TreeStatement parseExpressionStatement(TreeBuilder&);
     template <class TreeBuilder> TreeStatement parseExpressionOrLabelStatement(TreeBuilder&);
     template <class TreeBuilder> TreeStatement parseIfStatement(TreeBuilder&);
-    template <class TreeBuilder> ALWAYS_INLINE TreeStatement parseBlockStatement(TreeBuilder&);
+    template <class TreeBuilder> TreeStatement parseBlockStatement(TreeBuilder&);
     template <class TreeBuilder> TreeExpression parseExpression(TreeBuilder&);
+    template <class TreeBuilder> TreeExpression parseAssignmentExpression(TreeBuilder&, ExpressionErrorClassifier&);
     template <class TreeBuilder> TreeExpression parseAssignmentExpression(TreeBuilder&);
+    template <class TreeBuilder> TreeExpression parseAssignmentExpressionOrPropagateErrorClass(TreeBuilder&);
+    template <class TreeBuilder> TreeExpression parseYieldExpression(TreeBuilder&);
     template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseConditionalExpression(TreeBuilder&);
     template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseBinaryExpression(TreeBuilder&);
     template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseUnaryExpression(TreeBuilder&);
@@ -916,14 +1242,49 @@ private:
     template <class TreeBuilder> ALWAYS_INLINE TreeExpression parsePrimaryExpression(TreeBuilder&);
     template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseArrayLiteral(TreeBuilder&);
     template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseObjectLiteral(TreeBuilder&);
-    template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseStrictObjectLiteral(TreeBuilder&);
+    template <class TreeBuilder> NEVER_INLINE TreeExpression parseStrictObjectLiteral(TreeBuilder&);
+    template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseFunctionExpression(TreeBuilder&);
     template <class TreeBuilder> ALWAYS_INLINE TreeArguments parseArguments(TreeBuilder&);
-    template <bool strict, class TreeBuilder> ALWAYS_INLINE TreeProperty parseProperty(TreeBuilder&);
-    template <class TreeBuilder> ALWAYS_INLINE TreeFunctionBody parseFunctionBody(TreeBuilder&);
-    template <class TreeBuilder> ALWAYS_INLINE TreeFormalParameterList parseFormalParameters(TreeBuilder&);
-    template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseVarDeclarationList(TreeBuilder&, int& declarations, const Identifier*& lastIdent, TreeExpression& lastInitializer, JSTextPosition& identStart, JSTextPosition& initStart, JSTextPosition& initEnd);
-    template <class TreeBuilder> ALWAYS_INLINE TreeConstDeclList parseConstDeclarationList(TreeBuilder& context);
-    template <FunctionRequirements, bool nameIsInContainingScope, class TreeBuilder> bool parseFunctionInfo(TreeBuilder&, const Identifier*&, TreeFormalParameterList&, TreeFunctionBody&, unsigned& openBraceOffset, unsigned& closeBraceOffset, int& bodyStartLine, unsigned& bodyStartColumn);
+    template <class TreeBuilder> ALWAYS_INLINE TreeExpression parseArgument(TreeBuilder&, ArgumentType&);
+    template <class TreeBuilder> TreeProperty parseProperty(TreeBuilder&, bool strict);
+    template <class TreeBuilder> TreeExpression parsePropertyMethod(TreeBuilder& context, const Identifier* methodName, bool isGenerator);
+    template <class TreeBuilder> TreeProperty parseGetterSetter(TreeBuilder&, bool strict, PropertyNode::Type, unsigned getterOrSetterStartOffset, ConstructorKind = ConstructorKind::None, SuperBinding = SuperBinding::NotNeeded);
+    template <class TreeBuilder> ALWAYS_INLINE TreeFunctionBody parseFunctionBody(TreeBuilder&, const JSTokenLocation&, int, int functionKeywordStart, int functionNameStart, int parametersStart, ConstructorKind, SuperBinding, FunctionBodyType, unsigned, SourceParseMode);
+    template <class TreeBuilder> ALWAYS_INLINE bool parseFormalParameters(TreeBuilder&, TreeFormalParameterList, unsigned&);
+    enum VarDeclarationListContext { ForLoopContext, VarDeclarationContext };
+    template <class TreeBuilder> TreeExpression parseVariableDeclarationList(TreeBuilder&, int& declarations, TreeDestructuringPattern& lastPattern, TreeExpression& lastInitializer, JSTextPosition& identStart, JSTextPosition& initStart, JSTextPosition& initEnd, VarDeclarationListContext, DeclarationType, ExportType, bool& forLoopConstDoesNotHaveInitializer);
+    template <class TreeBuilder> TreeSourceElements parseArrowFunctionSingleExpressionBodySourceElements(TreeBuilder&);
+    template <class TreeBuilder> TreeExpression parseArrowFunctionExpression(TreeBuilder&);
+    template <class TreeBuilder> NEVER_INLINE TreeDestructuringPattern createBindingPattern(TreeBuilder&, DestructuringKind, ExportType, const Identifier&, JSToken, AssignmentContext, const Identifier** duplicateIdentifier);
+    template <class TreeBuilder> NEVER_INLINE TreeDestructuringPattern createAssignmentElement(TreeBuilder&, TreeExpression&, const JSTextPosition&, const JSTextPosition&);
+    template <class TreeBuilder> NEVER_INLINE TreeDestructuringPattern parseBindingOrAssignmentElement(TreeBuilder& context, DestructuringKind, ExportType, const Identifier** duplicateIdentifier, bool* hasDestructuringPattern, AssignmentContext bindingContext, int depth);
+    template <class TreeBuilder> NEVER_INLINE TreeDestructuringPattern parseAssignmentElement(TreeBuilder& context, DestructuringKind, ExportType, const Identifier** duplicateIdentifier, bool* hasDestructuringPattern, AssignmentContext bindingContext, int depth);
+    template <class TreeBuilder> NEVER_INLINE TreeDestructuringPattern parseDestructuringPattern(TreeBuilder&, DestructuringKind, ExportType, const Identifier** duplicateIdentifier = nullptr, bool* hasDestructuringPattern = nullptr, AssignmentContext = AssignmentContext::DeclarationStatement, int depth = 0);
+    template <class TreeBuilder> NEVER_INLINE TreeDestructuringPattern tryParseDestructuringPatternExpression(TreeBuilder&, AssignmentContext);
+    template <class TreeBuilder> NEVER_INLINE TreeExpression parseDefaultValueForDestructuringPattern(TreeBuilder&);
+    template <class TreeBuilder> TreeSourceElements parseModuleSourceElements(TreeBuilder&, SourceParseMode);
+    enum class ImportSpecifierType { NamespaceImport, NamedImport, DefaultImport };
+    template <class TreeBuilder> typename TreeBuilder::ImportSpecifier parseImportClauseItem(TreeBuilder&, ImportSpecifierType);
+    template <class TreeBuilder> typename TreeBuilder::ModuleName parseModuleName(TreeBuilder&);
+    template <class TreeBuilder> TreeStatement parseImportDeclaration(TreeBuilder&);
+    template <class TreeBuilder> typename TreeBuilder::ExportSpecifier parseExportSpecifier(TreeBuilder& context, Vector<const Identifier*>& maybeLocalNames, bool& hasKeywordForLocalBindings);
+    template <class TreeBuilder> TreeStatement parseExportDeclaration(TreeBuilder&);
+
+    enum class FunctionDefinitionType { Expression, Declaration, Method };
+    template <class TreeBuilder> NEVER_INLINE bool parseFunctionInfo(TreeBuilder&, FunctionRequirements, SourceParseMode, bool nameIsInContainingScope, ConstructorKind, SuperBinding, int functionKeywordStart, ParserFunctionInfo<TreeBuilder>&, FunctionDefinitionType);
+    
+    ALWAYS_INLINE bool isArrowFunctionParameters();
+    
+    template <class TreeBuilder> NEVER_INLINE int parseFunctionParameters(TreeBuilder&, SourceParseMode, ParserFunctionInfo<TreeBuilder>&);
+    template <class TreeBuilder> NEVER_INLINE typename TreeBuilder::FormalParameterList createGeneratorParameters(TreeBuilder&);
+
+    template <class TreeBuilder> NEVER_INLINE TreeClassExpression parseClass(TreeBuilder&, FunctionRequirements, ParserClassInfo<TreeBuilder>&);
+
+    template <class TreeBuilder> NEVER_INLINE typename TreeBuilder::TemplateString parseTemplateString(TreeBuilder& context, bool isTemplateHead, typename LexerType::RawStringsBuildMode, bool& elementIsTail);
+    template <class TreeBuilder> NEVER_INLINE typename TreeBuilder::TemplateLiteral parseTemplateLiteral(TreeBuilder&, typename LexerType::RawStringsBuildMode);
+
+    template <class TreeBuilder> ALWAYS_INLINE bool shouldCheckPropertyForUnderscoreProtoDuplicate(TreeBuilder&, const TreeProperty&);
+
     ALWAYS_INLINE int isBinaryOperator(JSTokenType);
     bool allowAutomaticSemicolon();
     
@@ -936,9 +1297,14 @@ private:
         return allowAutomaticSemicolon();
     }
     
+    void setEndOfStatement()
+    {
+        m_lexer->setTokenPosition(&m_token);
+    }
+
     bool canRecurse()
     {
-        return m_stack.isSafeToRecurse();
+        return m_vm->isSafeToRecurse();
     }
     
     const JSTextPosition& lastTokenEndPosition() const
@@ -951,30 +1317,114 @@ private:
         return !m_errorMessage.isNull();
     }
 
+    enum class FunctionParsePhase { Parameters, Body };
+    struct ParserState {
+        int assignmentCount { 0 };
+        int nonLHSCount { 0 };
+        int nonTrivialExpressionCount { 0 };
+        FunctionParsePhase functionParsePhase { FunctionParsePhase::Body };
+        const Identifier* lastIdentifier { nullptr };
+        const Identifier* lastFunctionName { nullptr };
+    };
+
+    // If you're using this directly, you probably should be using
+    // createSavePoint() instead.
+    ALWAYS_INLINE ParserState internalSaveParserState()
+    {
+        return m_parserState;
+    }
+
+    ALWAYS_INLINE void restoreParserState(const ParserState& state)
+    {
+        m_parserState = state;
+    }
+
+    struct LexerState {
+        int startOffset;
+        unsigned oldLineStartOffset;
+        unsigned oldLastLineNumber;
+        unsigned oldLineNumber;
+    };
+
+    // If you're using this directly, you probably should be using
+    // createSavePoint() instead.
+    // i.e, if you parse any kind of AssignmentExpression between
+    // saving/restoring, you should definitely not be using this directly.
+    ALWAYS_INLINE LexerState internalSaveLexerState()
+    {
+        LexerState result;
+        result.startOffset = m_token.m_location.startOffset;
+        result.oldLineStartOffset = m_token.m_location.lineStartOffset;
+        result.oldLastLineNumber = m_lexer->lastLineNumber();
+        result.oldLineNumber = m_lexer->lineNumber();
+        return result;
+    }
+
+    ALWAYS_INLINE void restoreLexerState(const LexerState& lexerState)
+    {
+        m_lexer->setOffset(lexerState.startOffset, lexerState.oldLineStartOffset);
+        next();
+        m_lexer->setLastLineNumber(lexerState.oldLastLineNumber);
+        m_lexer->setLineNumber(lexerState.oldLineNumber);
+    }
+
+    struct SavePoint {
+        ParserState parserState;
+        LexerState lexerState;
+    };
+    
+    ALWAYS_INLINE SavePoint createSavePointForError()
+    {
+        SavePoint result;
+        result.parserState = internalSaveParserState();
+        result.lexerState = internalSaveLexerState();
+        return result;
+    }
+    
+    ALWAYS_INLINE SavePoint createSavePoint()
+    {
+        ASSERT(!hasError());
+        return createSavePointForError();
+    }
+
+    ALWAYS_INLINE void restoreSavePointWithError(const SavePoint& savePoint, const String& message)
+    {
+        m_errorMessage = message;
+        restoreLexerState(savePoint.lexerState);
+        restoreParserState(savePoint.parserState);
+    }
+
+    ALWAYS_INLINE void restoreSavePoint(const SavePoint& savePoint)
+    {
+        restoreSavePointWithError(savePoint, String());
+    }
+
     VM* m_vm;
     const SourceCode* m_source;
-    ParserArena* m_arena;
-    OwnPtr<LexerType> m_lexer;
+    ParserArena m_parserArena;
+    std::unique_ptr<LexerType> m_lexer;
+    FunctionParameters* m_parameters { nullptr };
+
+    ParserState m_parserState;
     
-    VMStackBounds m_stack;
     bool m_hasStackOverflow;
     String m_errorMessage;
     JSToken m_token;
     bool m_allowsIn;
     JSTextPosition m_lastTokenEndPosition;
-    int m_assignmentCount;
-    int m_nonLHSCount;
     bool m_syntaxAlreadyValidated;
     int m_statementDepth;
-    int m_nonTrivialExpressionCount;
-    const Identifier* m_lastIdentifier;
     RefPtr<SourceProviderCache> m_functionCache;
     SourceElements* m_sourceElements;
-    ParserArenaData<DeclarationStacks::VarStack>* m_varDeclarations;
-    ParserArenaData<DeclarationStacks::FunctionStack>* m_funcDeclarations;
-    IdentifierSet m_capturedVariables;
+    bool m_parsingBuiltin;
+    SuperBinding m_superBinding;
+    ConstructorKind m_defaultConstructorKind;
+    ThisTDZMode m_thisTDZMode;
+    VariableEnvironment m_varDeclarations;
+    DeclarationStacks::FunctionStack m_funcDeclarations;
     CodeFeatures m_features;
     int m_numConstants;
+    ExpressionErrorClassifier* m_expressionErrorClassifier;
     
     struct DepthManager {
         DepthManager(int* depth)
@@ -997,13 +1447,13 @@ private:
 
 template <typename LexerType>
 template <class ParsedNode>
-PassRefPtr<ParsedNode> Parser<LexerType>::parse(ParserError& error)
+std::unique_ptr<ParsedNode> Parser<LexerType>::parse(ParserError& error, const Identifier& calleeName, SourceParseMode parseMode)
 {
     int errLine;
     String errMsg;
 
     if (ParsedNode::scopeIsFunction)
-        m_lexer->setIsReparsing();
+        m_lexer->setIsReparsingFunction();
 
     m_sourceElements = 0;
 
@@ -1011,9 +1461,10 @@ PassRefPtr<ParsedNode> Parser<LexerType>::parse(ParserError& error)
     errMsg = String();
 
     JSTokenLocation startLocation(tokenLocation());
-    unsigned startColumn = m_source->startColumn();
+    ASSERT(m_source->startColumn() > 0);
+    unsigned startColumn = m_source->startColumn() - 1;
 
-    String parseError = parseInner();
+    String parseError = parseInner(calleeName, parseMode);
 
     int lineNumber = m_lexer->lineNumber();
     bool lexError = m_lexer->sawError();
@@ -1027,24 +1478,33 @@ PassRefPtr<ParsedNode> Parser<LexerType>::parse(ParserError& error)
         m_sourceElements = 0;
     }
 
-    RefPtr<ParsedNode> result;
+    std::unique_ptr<ParsedNode> result;
     if (m_sourceElements) {
         JSTokenLocation endLocation;
-        endLocation.line = m_lexer->lastLineNumber();
+        endLocation.line = m_lexer->lineNumber();
         endLocation.lineStartOffset = m_lexer->currentLineStartOffset();
         endLocation.startOffset = m_lexer->currentOffset();
-        result = ParsedNode::create(m_vm,
+        unsigned endColumn = endLocation.startOffset - endLocation.lineStartOffset;
+        result = std::make_unique<ParsedNode>(m_parserArena,
                                     startLocation,
                                     endLocation,
                                     startColumn,
+                                    endColumn,
                                     m_sourceElements,
-                                    m_varDeclarations ? &m_varDeclarations->data : 0,
-                                    m_funcDeclarations ? &m_funcDeclarations->data : 0,
-                                    m_capturedVariables,
+                                    m_varDeclarations,
+                                    m_funcDeclarations,
+                                    currentScope()->finalizeLexicalEnvironment(),
+                                    m_parameters,
                                     *m_source,
                                     m_features,
                                     m_numConstants);
-        result->setLoc(m_source->firstLine(), m_lastTokenEndPosition.line, m_lexer->currentOffset(), m_lexer->currentLineStartOffset());
+        result->setLoc(m_source->firstLine(), m_lexer->lineNumber(), m_lexer->currentOffset(), m_lexer->currentLineStartOffset());
+        result->setEndOffset(m_lexer->currentOffset());
+
+        if (!isFunctionParseMode(parseMode)) {
+            m_source->provider()->setSourceURLDirective(m_lexer->sourceURL());
+            m_source->provider()->setSourceMappingURLDirective(m_lexer->sourceMappingURL());
+        }
     } else {
         // We can never see a syntax error when reparsing a function, since we should have
         // reported the error when parsing the containing program or eval code. So if we're
@@ -1052,14 +1512,19 @@ PassRefPtr<ParsedNode> Parser<LexerType>::parse(ParserError& error)
         // we ran out of stack while parsing. If we see an error while parsing eval or program
         // code we assume that it was a syntax error since running out of stack is much less
         // likely, and we are currently unable to distinguish between the two cases.
-        if (isFunctionBodyNode(static_cast<ParsedNode*>(0)) || m_hasStackOverflow)
+        if (isFunctionMetadataNode(static_cast<ParsedNode*>(0)) || m_hasStackOverflow)
             error = ParserError(ParserError::StackOverflow, ParserError::SyntaxErrorNone, m_token);
         else {
             ParserError::SyntaxErrorType errorType = ParserError::SyntaxErrorIrrecoverable;
             if (m_token.m_type == EOFTOK)
                 errorType = ParserError::SyntaxErrorRecoverable;
-            else if (m_token.m_type & UnterminatedErrorTokenFlag)
-                errorType = ParserError::SyntaxErrorUnterminatedLiteral;
+            else if (m_token.m_type & UnterminatedErrorTokenFlag) {
+                // Treat multiline capable unterminated literals as recoverable.
+                if (m_token.m_type == UNTERMINATED_MULTILINE_COMMENT_ERRORTOK || m_token.m_type == UNTERMINATED_TEMPLATE_LITERAL_ERRORTOK)
+                    errorType = ParserError::SyntaxErrorRecoverable;
+                else
+                    errorType = ParserError::SyntaxErrorUnterminatedLiteral;
+            }
             
             if (isEvalNode<ParsedNode>())
                 error = ParserError(ParserError::EvalError, errorType, m_token, errMsg, errLine);
@@ -1068,23 +1533,38 @@ PassRefPtr<ParsedNode> Parser<LexerType>::parse(ParserError& error)
         }
     }
 
-    m_arena->reset();
-
-    return result.release();
+    return result;
 }
 
 template <class ParsedNode>
-PassRefPtr<ParsedNode> parse(VM* vm, const SourceCode& source, FunctionParameters* parameters, const Identifier& name, JSParserStrictness strictness, JSParserMode parserMode, ParserError& error)
+std::unique_ptr<ParsedNode> parse(
+    VM* vm, const SourceCode& source,
+    const Identifier& name, JSParserBuiltinMode builtinMode,
+    JSParserStrictMode strictMode, SourceParseMode parseMode, SuperBinding superBinding,
+    ParserError& error, JSTextPosition* positionBeforeLastNewline = nullptr,
+    ConstructorKind defaultConstructorKind = ConstructorKind::None,
+    ThisTDZMode thisTDZMode = ThisTDZMode::CheckIfNeeded)
 {
     SamplingRegion samplingRegion("Parsing");
 
     ASSERT(!source.provider()->source().isNull());
     if (source.provider()->source().is8Bit()) {
-        Parser< Lexer<LChar> > parser(vm, source, parameters, name, strictness, parserMode);
-        return parser.parse<ParsedNode>(error);
+        Parser<Lexer<LChar>> parser(vm, source, builtinMode, strictMode, parseMode, superBinding, defaultConstructorKind, thisTDZMode);
+        std::unique_ptr<ParsedNode> result = parser.parse<ParsedNode>(error, name, parseMode);
+        if (positionBeforeLastNewline)
+            *positionBeforeLastNewline = parser.positionBeforeLastNewline();
+        if (builtinMode == JSParserBuiltinMode::Builtin) {
+            if (!result)
+                WTF::dataLog("Error compiling builtin: ", error.message(), "\n");
+        }
+        return result;
     }
-    Parser< Lexer<UChar> > parser(vm, source, parameters, name, strictness, parserMode);
-    return parser.parse<ParsedNode>(error);
+    ASSERT_WITH_MESSAGE(defaultConstructorKind == ConstructorKind::None, "BuiltinExecutables::createDefaultConstructor should always use a 8-bit string");
+    Parser<Lexer<UChar>> parser(vm, source, builtinMode, strictMode, parseMode, superBinding, defaultConstructorKind, thisTDZMode);
+    std::unique_ptr<ParsedNode> result = parser.parse<ParsedNode>(error, name, parseMode);
+    if (positionBeforeLastNewline)
+        *positionBeforeLastNewline = parser.positionBeforeLastNewline();
+    return result;
 }
 
 } // namespace