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diff --git a/js/src/frontend/SyntaxParseHandler.h b/js/src/frontend/SyntaxParseHandler.h
new file mode 100644
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+++ b/js/src/frontend/SyntaxParseHandler.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef frontend_SyntaxParseHandler_h
+#define frontend_SyntaxParseHandler_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Maybe.h"  // mozilla::Maybe
+
+#include <string.h>
+
+#include "jstypes.h"
+
+#include "frontend/CompilationStencil.h"  // CompilationState
+#include "frontend/FunctionSyntaxKind.h"  // FunctionSyntaxKind
+#include "frontend/NameAnalysisTypes.h"   // PrivateNameKind
+#include "frontend/ParseNode.h"
+#include "frontend/ParserAtom.h"  // TaggedParserAtomIndex
+#include "frontend/TokenStream.h"
+
+namespace js {
+
+namespace frontend {
+
+// Parse handler used when processing the syntax in a block of code, to generate
+// the minimal information which is required to detect syntax errors and allow
+// bytecode to be emitted for outer functions.
+//
+// When parsing, we start at the top level with a full parse, and when possible
+// only check the syntax for inner functions, so that they can be lazily parsed
+// into bytecode when/if they first run. Checking the syntax of a function is
+// several times faster than doing a full parse/emit, and lazy parsing improves
+// both performance and memory usage significantly when pages contain large
+// amounts of code that never executes (which happens often).
+class SyntaxParseHandler {
+  // Remember the last encountered name or string literal during syntax parses.
+  TaggedParserAtomIndex lastAtom;
+  TokenPos lastStringPos;
+
+ public:
+  enum Node {
+    NodeFailure = 0,
+    NodeGeneric,
+    NodeGetProp,
+    NodeStringExprStatement,
+    NodeReturn,
+    NodeBreak,
+    NodeThrow,
+    NodeEmptyStatement,
+
+    NodeVarDeclaration,
+    NodeLexicalDeclaration,
+
+    // A non-arrow function expression with block body, from bog-standard
+    // ECMAScript.
+    NodeFunctionExpression,
+
+    NodeFunctionArrow,
+    NodeFunctionStatement,
+
+    // This is needed for proper assignment-target handling.  ES6 formally
+    // requires function calls *not* pass IsValidSimpleAssignmentTarget,
+    // but at last check there were still sites with |f() = 5| and similar
+    // in code not actually executed (or at least not executed enough to be
+    // noticed).
+    NodeFunctionCall,
+
+    NodeOptionalFunctionCall,
+
+    // Node representing normal names which don't require any special
+    // casing.
+    NodeName,
+
+    // Nodes representing the names "arguments" and "eval".
+    NodeArgumentsName,
+    NodeEvalName,
+
+    // Node representing the "async" name, which may actually be a
+    // contextual keyword.
+    NodePotentialAsyncKeyword,
+
+    // Node representing private names.
+    NodePrivateName,
+
+    NodeDottedProperty,
+    NodeOptionalDottedProperty,
+    NodeElement,
+    NodeOptionalElement,
+    // A distinct node for [PrivateName], to make detecting delete this.#x
+    // detectable in syntax parse
+    NodePrivateMemberAccess,
+    NodeOptionalPrivateMemberAccess,
+
+    // Destructuring target patterns can't be parenthesized: |([a]) = [3];|
+    // must be a syntax error.  (We can't use NodeGeneric instead of these
+    // because that would trigger invalid-left-hand-side ReferenceError
+    // semantics when SyntaxError semantics are desired.)
+    NodeParenthesizedArray,
+    NodeParenthesizedObject,
+
+    // In rare cases a parenthesized |node| doesn't have the same semantics
+    // as |node|.  Each such node has a special Node value, and we use a
+    // different Node value to represent the parenthesized form.  See also
+    // is{Unp,P}arenthesized*(Node), parenthesize(Node), and the various
+    // functions that deal in NodeUnparenthesized* below.
+
+    // Valuable for recognizing potential destructuring patterns.
+    NodeUnparenthesizedArray,
+    NodeUnparenthesizedObject,
+
+    // The directive prologue at the start of a FunctionBody or ScriptBody
+    // is the longest sequence (possibly empty) of string literal
+    // expression statements at the start of a function.  Thus we need this
+    // to treat |"use strict";| as a possible Use Strict Directive and
+    // |("use strict");| as a useless statement.
+    NodeUnparenthesizedString,
+
+    // For destructuring patterns an assignment element with
+    // an initializer expression is not allowed be parenthesized.
+    // i.e. |{x = 1} = obj|
+    NodeUnparenthesizedAssignment,
+
+    // This node is necessary to determine if the base operand in an
+    // exponentiation operation is an unparenthesized unary expression.
+    // We want to reject |-2 ** 3|, but still need to allow |(-2) ** 3|.
+    NodeUnparenthesizedUnary,
+
+    // This node is necessary to determine if the LHS of a property access is
+    // super related.
+    NodeSuperBase
+  };
+
+#define DECLARE_TYPE(typeName, longTypeName, asMethodName) \
+  using longTypeName = Node;
+  FOR_EACH_PARSENODE_SUBCLASS(DECLARE_TYPE)
+#undef DECLARE_TYPE
+
+  using NullNode = Node;
+
+  bool isNonArrowFunctionExpression(Node node) const {
+    return node == NodeFunctionExpression;
+  }
+
+  bool isPropertyOrPrivateMemberAccess(Node node) {
+    return node == NodeDottedProperty || node == NodeElement ||
+           node == NodePrivateMemberAccess;
+  }
+
+  bool isOptionalPropertyOrPrivateMemberAccess(Node node) {
+    return node == NodeOptionalDottedProperty || node == NodeOptionalElement ||
+           node == NodeOptionalPrivateMemberAccess;
+  }
+
+  bool isFunctionCall(Node node) {
+    // Note: super() is a special form, *not* a function call.
+    return node == NodeFunctionCall;
+  }
+
+  static bool isUnparenthesizedDestructuringPattern(Node node) {
+    return node == NodeUnparenthesizedArray ||
+           node == NodeUnparenthesizedObject;
+  }
+
+  static bool isParenthesizedDestructuringPattern(Node node) {
+    // Technically this isn't a destructuring target at all -- the grammar
+    // doesn't treat it as such.  But we need to know when this happens to
+    // consider it a SyntaxError rather than an invalid-left-hand-side
+    // ReferenceError.
+    return node == NodeParenthesizedArray || node == NodeParenthesizedObject;
+  }
+
+ public:
+  SyntaxParseHandler(FrontendContext* fc, CompilationState& compilationState) {
+    MOZ_ASSERT(!compilationState.input.isDelazifying());
+  }
+
+  static NullNode null() { return NodeFailure; }
+
+#define DECLARE_AS(typeName, longTypeName, asMethodName) \
+  static longTypeName asMethodName(Node node) { return node; }
+  FOR_EACH_PARSENODE_SUBCLASS(DECLARE_AS)
+#undef DECLARE_AS
+
+  NameNodeType newName(TaggedParserAtomIndex name, const TokenPos& pos) {
+    lastAtom = name;
+    if (name == TaggedParserAtomIndex::WellKnown::arguments()) {
+      return NodeArgumentsName;
+    }
+    if (pos.begin + strlen("async") == pos.end &&
+        name == TaggedParserAtomIndex::WellKnown::async()) {
+      return NodePotentialAsyncKeyword;
+    }
+    if (name == TaggedParserAtomIndex::WellKnown::eval()) {
+      return NodeEvalName;
+    }
+    return NodeName;
+  }
+
+  UnaryNodeType newComputedName(Node expr, uint32_t start, uint32_t end) {
+    return NodeGeneric;
+  }
+
+  UnaryNodeType newSyntheticComputedName(Node expr, uint32_t start,
+                                         uint32_t end) {
+    return NodeGeneric;
+  }
+
+  NameNodeType newObjectLiteralPropertyName(TaggedParserAtomIndex atom,
+                                            const TokenPos& pos) {
+    return NodeName;
+  }
+
+  NameNodeType newPrivateName(TaggedParserAtomIndex atom, const TokenPos& pos) {
+    return NodePrivateName;
+  }
+
+  NumericLiteralType newNumber(double value, DecimalPoint decimalPoint,
+                               const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  BigIntLiteralType newBigInt() { return NodeGeneric; }
+
+  BooleanLiteralType newBooleanLiteral(bool cond, const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  NameNodeType newStringLiteral(TaggedParserAtomIndex atom,
+                                const TokenPos& pos) {
+    lastAtom = atom;
+    lastStringPos = pos;
+    return NodeUnparenthesizedString;
+  }
+
+  NameNodeType newTemplateStringLiteral(TaggedParserAtomIndex atom,
+                                        const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  CallSiteNodeType newCallSiteObject(uint32_t begin) { return NodeGeneric; }
+
+  void addToCallSiteObject(CallSiteNodeType callSiteObj, Node rawNode,
+                           Node cookedNode) {}
+
+  ThisLiteralType newThisLiteral(const TokenPos& pos, Node thisName) {
+    return NodeGeneric;
+  }
+  NullLiteralType newNullLiteral(const TokenPos& pos) { return NodeGeneric; }
+  RawUndefinedLiteralType newRawUndefinedLiteral(const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  RegExpLiteralType newRegExp(Node reobj, const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  ConditionalExpressionType newConditional(Node cond, Node thenExpr,
+                                           Node elseExpr) {
+    return NodeGeneric;
+  }
+
+  UnaryNodeType newDelete(uint32_t begin, Node expr) {
+    return NodeUnparenthesizedUnary;
+  }
+
+  UnaryNodeType newTypeof(uint32_t begin, Node kid) {
+    return NodeUnparenthesizedUnary;
+  }
+
+  UnaryNodeType newUnary(ParseNodeKind kind, uint32_t begin, Node kid) {
+    return NodeUnparenthesizedUnary;
+  }
+
+  UnaryNodeType newUpdate(ParseNodeKind kind, uint32_t begin, Node kid) {
+    return NodeGeneric;
+  }
+
+  UnaryNodeType newSpread(uint32_t begin, Node kid) { return NodeGeneric; }
+
+  Node appendOrCreateList(ParseNodeKind kind, Node left, Node right,
+                          ParseContext* pc) {
+    return NodeGeneric;
+  }
+
+  // Expressions
+
+  ListNodeType newArrayLiteral(uint32_t begin) {
+    return NodeUnparenthesizedArray;
+  }
+  [[nodiscard]] bool addElision(ListNodeType literal, const TokenPos& pos) {
+    return true;
+  }
+  [[nodiscard]] bool addSpreadElement(ListNodeType literal, uint32_t begin,
+                                      Node inner) {
+    return true;
+  }
+  void addArrayElement(ListNodeType literal, Node element) {}
+
+  ListNodeType newArguments(const TokenPos& pos) { return NodeGeneric; }
+  CallNodeType newCall(Node callee, Node args, JSOp callOp) {
+    return NodeFunctionCall;
+  }
+
+  CallNodeType newOptionalCall(Node callee, Node args, JSOp callOp) {
+    return NodeOptionalFunctionCall;
+  }
+
+  CallNodeType newSuperCall(Node callee, Node args, bool isSpread) {
+    return NodeGeneric;
+  }
+  CallNodeType newTaggedTemplate(Node tag, Node args, JSOp callOp) {
+    return NodeGeneric;
+  }
+
+  ListNodeType newObjectLiteral(uint32_t begin) {
+    return NodeUnparenthesizedObject;
+  }
+
+#ifdef ENABLE_RECORD_TUPLE
+  ListNodeType newRecordLiteral(uint32_t begin) { return NodeGeneric; }
+
+  ListNodeType newTupleLiteral(uint32_t begin) { return NodeGeneric; }
+#endif
+
+  ListNodeType newClassMemberList(uint32_t begin) { return NodeGeneric; }
+  ClassNamesType newClassNames(Node outer, Node inner, const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  ClassNodeType newClass(Node name, Node heritage, Node methodBlock,
+#ifdef ENABLE_DECORATORS
+                         ListNodeType decorators,
+#endif
+                         const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  LexicalScopeNodeType newLexicalScope(Node body) {
+    return NodeLexicalDeclaration;
+  }
+
+  ClassBodyScopeNodeType newClassBodyScope(Node body) {
+    return NodeLexicalDeclaration;
+  }
+
+  NewTargetNodeType newNewTarget(NullaryNodeType newHolder,
+                                 NullaryNodeType targetHolder,
+                                 NameNodeType newTargetName) {
+    return NodeGeneric;
+  }
+  NullaryNodeType newPosHolder(const TokenPos& pos) { return NodeGeneric; }
+  UnaryNodeType newSuperBase(Node thisName, const TokenPos& pos) {
+    return NodeSuperBase;
+  }
+
+  [[nodiscard]] bool addPrototypeMutation(ListNodeType literal, uint32_t begin,
+                                          Node expr) {
+    return true;
+  }
+  BinaryNodeType newPropertyDefinition(Node key, Node val) {
+    return NodeGeneric;
+  }
+  void addPropertyDefinition(ListNodeType literal, BinaryNodeType propdef) {}
+  [[nodiscard]] bool addPropertyDefinition(ListNodeType literal, Node key,
+                                           Node expr) {
+    return true;
+  }
+  [[nodiscard]] bool addShorthand(ListNodeType literal, NameNodeType name,
+                                  NameNodeType expr) {
+    return true;
+  }
+  [[nodiscard]] bool addSpreadProperty(ListNodeType literal, uint32_t begin,
+                                       Node inner) {
+    return true;
+  }
+  [[nodiscard]] bool addObjectMethodDefinition(ListNodeType literal, Node key,
+                                               FunctionNodeType funNode,
+                                               AccessorType atype) {
+    return true;
+  }
+  [[nodiscard]] Node newDefaultClassConstructor(Node key,
+                                                FunctionNodeType funNode) {
+    return NodeGeneric;
+  }
+  [[nodiscard]] Node newClassMethodDefinition(
+      Node key, FunctionNodeType funNode, AccessorType atype, bool isStatic,
+      mozilla::Maybe<FunctionNodeType> initializerIfPrivate
+#ifdef ENABLE_DECORATORS
+      ,
+      ListNodeType decorators
+#endif
+  ) {
+    return NodeGeneric;
+  }
+  [[nodiscard]] Node newClassFieldDefinition(Node name,
+                                             FunctionNodeType initializer,
+                                             bool isStatic
+#ifdef ENABLE_DECORATORS
+                                             ,
+                                             ListNodeType decorators,
+                                             bool hasAccessor
+#endif
+  ) {
+    return NodeGeneric;
+  }
+
+  [[nodiscard]] Node newStaticClassBlock(FunctionNodeType block) {
+    return NodeGeneric;
+  }
+
+  [[nodiscard]] bool addClassMemberDefinition(ListNodeType memberList,
+                                              Node member) {
+    return true;
+  }
+  UnaryNodeType newYieldExpression(uint32_t begin, Node value) {
+    return NodeGeneric;
+  }
+  UnaryNodeType newYieldStarExpression(uint32_t begin, Node value) {
+    return NodeGeneric;
+  }
+  UnaryNodeType newAwaitExpression(uint32_t begin, Node value) {
+    return NodeUnparenthesizedUnary;
+  }
+  UnaryNodeType newOptionalChain(uint32_t begin, Node value) {
+    return NodeGeneric;
+  }
+
+  // Statements
+
+  ListNodeType newStatementList(const TokenPos& pos) { return NodeGeneric; }
+  void addStatementToList(ListNodeType list, Node stmt) {}
+  void setListEndPosition(ListNodeType list, const TokenPos& pos) {}
+  void addCaseStatementToList(ListNodeType list, CaseClauseType caseClause) {}
+  [[nodiscard]] bool prependInitialYield(ListNodeType stmtList, Node genName) {
+    return true;
+  }
+  NullaryNodeType newEmptyStatement(const TokenPos& pos) {
+    return NodeEmptyStatement;
+  }
+
+  BinaryNodeType newImportAssertion(Node keyNode, Node valueNode) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newModuleRequest(Node moduleSpec, Node importAssertionList,
+                                  const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newImportDeclaration(Node importSpecSet, Node moduleRequest,
+                                      const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newImportSpec(Node importNameNode, Node bindingName) {
+    return NodeGeneric;
+  }
+  UnaryNodeType newImportNamespaceSpec(uint32_t begin, Node bindingName) {
+    return NodeGeneric;
+  }
+  UnaryNodeType newExportDeclaration(Node kid, const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newExportFromDeclaration(uint32_t begin, Node exportSpecSet,
+                                          Node moduleRequest) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newExportDefaultDeclaration(Node kid, Node maybeBinding,
+                                             const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newExportSpec(Node bindingName, Node exportName) {
+    return NodeGeneric;
+  }
+  UnaryNodeType newExportNamespaceSpec(uint32_t begin, Node exportName) {
+    return NodeGeneric;
+  }
+  NullaryNodeType newExportBatchSpec(const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newImportMeta(NullaryNodeType importHolder,
+                               NullaryNodeType metaHolder) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newCallImport(NullaryNodeType importHolder, Node singleArg) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newCallImportSpec(Node specifierArg, Node optionalArg) {
+    return NodeGeneric;
+  }
+
+  BinaryNodeType newSetThis(Node thisName, Node value) { return value; }
+
+  UnaryNodeType newExprStatement(Node expr, uint32_t end) {
+    return expr == NodeUnparenthesizedString ? NodeStringExprStatement
+                                             : NodeGeneric;
+  }
+
+  TernaryNodeType newIfStatement(uint32_t begin, Node cond, Node thenBranch,
+                                 Node elseBranch) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newDoWhileStatement(Node body, Node cond,
+                                     const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  BinaryNodeType newWhileStatement(uint32_t begin, Node cond, Node body) {
+    return NodeGeneric;
+  }
+  SwitchStatementType newSwitchStatement(
+      uint32_t begin, Node discriminant,
+      LexicalScopeNodeType lexicalForCaseList, bool hasDefault) {
+    return NodeGeneric;
+  }
+  CaseClauseType newCaseOrDefault(uint32_t begin, Node expr, Node body) {
+    return NodeGeneric;
+  }
+  ContinueStatementType newContinueStatement(TaggedParserAtomIndex label,
+                                             const TokenPos& pos) {
+    return NodeGeneric;
+  }
+  BreakStatementType newBreakStatement(TaggedParserAtomIndex label,
+                                       const TokenPos& pos) {
+    return NodeBreak;
+  }
+  UnaryNodeType newReturnStatement(Node expr, const TokenPos& pos) {
+    return NodeReturn;
+  }
+  UnaryNodeType newExpressionBody(Node expr) { return NodeReturn; }
+  BinaryNodeType newWithStatement(uint32_t begin, Node expr, Node body) {
+    return NodeGeneric;
+  }
+
+  LabeledStatementType newLabeledStatement(TaggedParserAtomIndex label,
+                                           Node stmt, uint32_t begin) {
+    return NodeGeneric;
+  }
+
+  UnaryNodeType newThrowStatement(Node expr, const TokenPos& pos) {
+    return NodeThrow;
+  }
+  TernaryNodeType newTryStatement(uint32_t begin, Node body,
+                                  LexicalScopeNodeType catchScope,
+                                  Node finallyBlock) {
+    return NodeGeneric;
+  }
+  DebuggerStatementType newDebuggerStatement(const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  NameNodeType newPropertyName(TaggedParserAtomIndex name,
+                               const TokenPos& pos) {
+    lastAtom = name;
+    return NodeGeneric;
+  }
+
+  PropertyAccessType newPropertyAccess(Node expr, NameNodeType key) {
+    return NodeDottedProperty;
+  }
+
+  PropertyAccessType newOptionalPropertyAccess(Node expr, NameNodeType key) {
+    return NodeOptionalDottedProperty;
+  }
+
+  PropertyByValueType newPropertyByValue(Node lhs, Node index, uint32_t end) {
+    MOZ_ASSERT(!isPrivateName(index));
+    return NodeElement;
+  }
+
+  PropertyByValueType newOptionalPropertyByValue(Node lhs, Node index,
+                                                 uint32_t end) {
+    return NodeOptionalElement;
+  }
+
+  PrivateMemberAccessType newPrivateMemberAccess(Node lhs, Node privateName,
+                                                 uint32_t end) {
+    return NodePrivateMemberAccess;
+  }
+
+  PrivateMemberAccessType newOptionalPrivateMemberAccess(Node lhs,
+                                                         Node privateName,
+                                                         uint32_t end) {
+    return NodeOptionalPrivateMemberAccess;
+  }
+
+  [[nodiscard]] bool setupCatchScope(LexicalScopeNodeType lexicalScope,
+                                     Node catchName, Node catchBody) {
+    return true;
+  }
+
+  [[nodiscard]] bool setLastFunctionFormalParameterDefault(
+      FunctionNodeType funNode, Node defaultValue) {
+    return true;
+  }
+
+  void checkAndSetIsDirectRHSAnonFunction(Node pn) {}
+
+  ParamsBodyNodeType newParamsBody(const TokenPos& pos) { return NodeGeneric; }
+
+  FunctionNodeType newFunction(FunctionSyntaxKind syntaxKind,
+                               const TokenPos& pos) {
+    switch (syntaxKind) {
+      case FunctionSyntaxKind::Statement:
+        return NodeFunctionStatement;
+      case FunctionSyntaxKind::Arrow:
+        return NodeFunctionArrow;
+      default:
+        // All non-arrow function expressions are initially presumed to have
+        // block body.  This will be overridden later *if* the function
+        // expression permissibly has an AssignmentExpression body.
+        return NodeFunctionExpression;
+    }
+  }
+
+  void setFunctionFormalParametersAndBody(FunctionNodeType funNode,
+                                          ParamsBodyNodeType paramsBody) {}
+  void setFunctionBody(FunctionNodeType funNode, LexicalScopeNodeType body) {}
+  void setFunctionBox(FunctionNodeType funNode, FunctionBox* funbox) {}
+  void addFunctionFormalParameter(FunctionNodeType funNode, Node argpn) {}
+
+  ForNodeType newForStatement(uint32_t begin, TernaryNodeType forHead,
+                              Node body, unsigned iflags) {
+    return NodeGeneric;
+  }
+
+  TernaryNodeType newForHead(Node init, Node test, Node update,
+                             const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  TernaryNodeType newForInOrOfHead(ParseNodeKind kind, Node target,
+                                   Node iteratedExpr, const TokenPos& pos) {
+    return NodeGeneric;
+  }
+
+  AssignmentNodeType finishInitializerAssignment(NameNodeType nameNode,
+                                                 Node init) {
+    return NodeUnparenthesizedAssignment;
+  }
+
+  void setBeginPosition(Node pn, Node oth) {}
+  void setBeginPosition(Node pn, uint32_t begin) {}
+
+  void setEndPosition(Node pn, Node oth) {}
+  void setEndPosition(Node pn, uint32_t end) {}
+
+  uint32_t getFunctionNameOffset(Node func, TokenStreamAnyChars& ts) {
+    // XXX This offset isn't relevant to the offending function name.  But
+    //     we may not *have* that function name around, because of how lazy
+    //     parsing works -- the actual name could be outside
+    //     |tokenStream.userbuf|'s observed region.  So the current offset
+    //     is the best we can do.
+    return ts.currentToken().pos.begin;
+  }
+
+  ListNodeType newList(ParseNodeKind kind, const TokenPos& pos) {
+    MOZ_ASSERT(kind != ParseNodeKind::VarStmt);
+    MOZ_ASSERT(kind != ParseNodeKind::LetDecl);
+    MOZ_ASSERT(kind != ParseNodeKind::ConstDecl);
+    MOZ_ASSERT(kind != ParseNodeKind::ParamsBody);
+    return NodeGeneric;
+  }
+
+  ListNodeType newList(ParseNodeKind kind, Node kid) {
+    return newList(kind, TokenPos());
+  }
+
+  DeclarationListNodeType newDeclarationList(ParseNodeKind kind,
+                                             const TokenPos& pos) {
+    if (kind == ParseNodeKind::VarStmt) {
+      return NodeVarDeclaration;
+    }
+    MOZ_ASSERT(kind == ParseNodeKind::LetDecl ||
+               kind == ParseNodeKind::ConstDecl);
+    return NodeLexicalDeclaration;
+  }
+
+  ListNodeType newCommaExpressionList(Node kid) { return NodeGeneric; }
+
+  void addList(ListNodeType list, Node kid) {
+    MOZ_ASSERT(list == NodeGeneric || list == NodeUnparenthesizedArray ||
+               list == NodeUnparenthesizedObject ||
+               list == NodeVarDeclaration || list == NodeLexicalDeclaration ||
+               list == NodeFunctionCall);
+  }
+
+  CallNodeType newNewExpression(uint32_t begin, Node ctor, Node args,
+                                bool isSpread) {
+    return NodeGeneric;
+  }
+
+  AssignmentNodeType newAssignment(ParseNodeKind kind, Node lhs, Node rhs) {
+    return kind == ParseNodeKind::AssignExpr ? NodeUnparenthesizedAssignment
+                                             : NodeGeneric;
+  }
+
+  AssignmentNodeType newInitExpr(Node lhs, Node rhs) { return NodeGeneric; }
+
+  bool isUnparenthesizedAssignment(Node node) {
+    return node == NodeUnparenthesizedAssignment;
+  }
+
+  bool isUnparenthesizedUnaryExpression(Node node) {
+    return node == NodeUnparenthesizedUnary;
+  }
+
+  bool isReturnStatement(Node node) { return node == NodeReturn; }
+
+  bool isStatementPermittedAfterReturnStatement(Node pn) {
+    return pn == NodeFunctionStatement || isNonArrowFunctionExpression(pn) ||
+           pn == NodeVarDeclaration || pn == NodeBreak || pn == NodeThrow ||
+           pn == NodeEmptyStatement;
+  }
+
+  bool isSuperBase(Node pn) { return pn == NodeSuperBase; }
+
+  void setListHasNonConstInitializer(ListNodeType literal) {}
+  [[nodiscard]] Node parenthesize(Node node) {
+    // A number of nodes have different behavior upon parenthesization, but
+    // only in some circumstances.  Convert these nodes to special
+    // parenthesized forms.
+    if (node == NodeUnparenthesizedArray) {
+      return NodeParenthesizedArray;
+    }
+    if (node == NodeUnparenthesizedObject) {
+      return NodeParenthesizedObject;
+    }
+
+    // Other nodes need not be recognizable after parenthesization; convert
+    // them to a generic node.
+    if (node == NodeUnparenthesizedString ||
+        node == NodeUnparenthesizedAssignment ||
+        node == NodeUnparenthesizedUnary) {
+      return NodeGeneric;
+    }
+
+    // Convert parenthesized |async| to a normal name node.
+    if (node == NodePotentialAsyncKeyword) {
+      return NodeName;
+    }
+
+    // In all other cases, the parenthesized form of |node| is equivalent
+    // to the unparenthesized form: return |node| unchanged.
+    return node;
+  }
+  template <typename NodeType>
+  [[nodiscard]] NodeType setLikelyIIFE(NodeType node) {
+    return node;  // Remain in syntax-parse mode.
+  }
+
+  bool isName(Node node) {
+    return node == NodeName || node == NodeArgumentsName ||
+           node == NodeEvalName || node == NodePotentialAsyncKeyword;
+  }
+
+  bool isArgumentsName(Node node) { return node == NodeArgumentsName; }
+  bool isEvalName(Node node) { return node == NodeEvalName; }
+  bool isAsyncKeyword(Node node) { return node == NodePotentialAsyncKeyword; }
+
+  bool isPrivateName(Node node) { return node == NodePrivateName; }
+  bool isPrivateMemberAccess(Node node) {
+    return node == NodePrivateMemberAccess;
+  }
+
+  TaggedParserAtomIndex maybeDottedProperty(Node node) {
+    // Note: |super.apply(...)| is a special form that calls an "apply"
+    // method retrieved from one value, but using a *different* value as
+    // |this|.  It's not really eligible for the funapply/funcall
+    // optimizations as they're currently implemented (assuming a single
+    // value is used for both retrieval and |this|).
+    if (node != NodeDottedProperty && node != NodeOptionalDottedProperty) {
+      return TaggedParserAtomIndex::null();
+    }
+    return lastAtom;
+  }
+
+  TaggedParserAtomIndex isStringExprStatement(Node pn, TokenPos* pos) {
+    if (pn == NodeStringExprStatement) {
+      *pos = lastStringPos;
+      return lastAtom;
+    }
+    return TaggedParserAtomIndex::null();
+  }
+
+  bool reuseLazyInnerFunctions() { return false; }
+  bool reuseClosedOverBindings() { return false; }
+  TaggedParserAtomIndex nextLazyClosedOverBinding() {
+    MOZ_CRASH(
+        "SyntaxParseHandler::canSkipLazyClosedOverBindings must return false");
+  }
+
+  void setPrivateNameKind(Node node, PrivateNameKind kind) {}
+};
+
+}  // namespace frontend
+}  // namespace js
+
+#endif /* frontend_SyntaxParseHandler_h */