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diff --git a/js/src/frontend/ForOfEmitter.h b/js/src/frontend/ForOfEmitter.h
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+++ b/js/src/frontend/ForOfEmitter.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_ForOfEmitter_h
+#define frontend_ForOfEmitter_h
+
+#include "mozilla/Attributes.h"  // MOZ_STACK_CLASS
+#include "mozilla/Maybe.h"       // mozilla::Maybe
+
+#include <stdint.h>  // int32_t
+
+#include "frontend/ForOfLoopControl.h"  // ForOfLoopControl
+#include "frontend/IteratorKind.h"      // IteratorKind
+#include "frontend/SelfHostedIter.h"    // SelfHostedIter
+#include "frontend/TDZCheckCache.h"     // TDZCheckCache
+
+namespace js {
+namespace frontend {
+
+struct BytecodeEmitter;
+class EmitterScope;
+
+// Class for emitting bytecode for for-of loop.
+//
+// Usage: (check for the return value is omitted for simplicity)
+//
+//   `for (init of iterated) body`
+//     // headLexicalEmitterScope: lexical scope for init
+//     ForOfEmitter forOf(this, headLexicalEmitterScope);
+//     forOf.emitIterated();
+//     emit(iterated);
+//     forOf.emitInitialize(offset_of_for);
+//     emit(init);
+//     forOf.emitBody();
+//     emit(body);
+//     forOf.emitEnd(offset_of_iterated);
+//
+class MOZ_STACK_CLASS ForOfEmitter {
+  BytecodeEmitter* bce_;
+
+#ifdef DEBUG
+  // The stack depth before emitting IteratorNext code inside loop.
+  int32_t loopDepth_ = 0;
+#endif
+
+  SelfHostedIter selfHostedIter_;
+  IteratorKind iterKind_;
+
+  mozilla::Maybe<ForOfLoopControl> loopInfo_;
+
+  // The lexical scope to be freshened for each iteration.
+  // See the comment in `emitBody` for more details.
+  const EmitterScope* headLexicalEmitterScope_;
+
+  // Cache for the iterated value.
+  // (The cache for the iteration body is inside `loopInfo_`)
+  mozilla::Maybe<TDZCheckCache> tdzCacheForIteratedValue_;
+
+#ifdef DEBUG
+  // The state of this emitter.
+  //
+  // +-------+ emitIterated +----------+ emitInitialize +------------+
+  // | Start |------------->| Iterated |--------------->| Initialize |-+
+  // +-------+              +----------+                +------------+ |
+  //                                                                   |
+  //                                +----------------------------------+
+  //                                |
+  //                                | emitBody +------+ emitEnd  +-----+
+  //                                +----------| Body |--------->| End |
+  //                                           +------+          +-----+
+  enum class State {
+    // The initial state.
+    Start,
+
+    // After calling emitIterated.
+    Iterated,
+
+    // After calling emitInitialize.
+    Initialize,
+
+    // After calling emitBody.
+    Body,
+
+    // After calling emitEnd.
+    End
+  };
+  State state_ = State::Start;
+#endif
+
+ public:
+  ForOfEmitter(BytecodeEmitter* bce,
+               const EmitterScope* headLexicalEmitterScope,
+               SelfHostedIter selfHostedIter, IteratorKind iterKind);
+
+  // The offset in the source code for each character below:
+  //
+  //   for ( var x of obj ) { ... }
+  //   ^              ^
+  //   |              |
+  //   |              iteratedPos
+  //   |
+  //   forPos
+  [[nodiscard]] bool emitIterated();
+  [[nodiscard]] bool emitInitialize(uint32_t forPos);
+  [[nodiscard]] bool emitBody();
+  [[nodiscard]] bool emitEnd(uint32_t iteratedPos);
+};
+
+} /* namespace frontend */
+} /* namespace js */
+
+#endif /* frontend_ForOfEmitter_h */