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diff --git a/js/src/frontend/EmitterScope.h b/js/src/frontend/EmitterScope.h
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+++ b/js/src/frontend/EmitterScope.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_EmitterScope_h
+#define frontend_EmitterScope_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+
+#include <stdint.h>
+
+#include "ds/Nestable.h"
+#include "frontend/AbstractScopePtr.h"
+#include "frontend/NameAnalysisTypes.h"
+#include "frontend/NameCollections.h"
+#include "frontend/ParseContext.h"
+#include "frontend/SharedContext.h"
+#include "js/TypeDecls.h"
+#include "vm/BytecodeUtil.h"   // JSOp
+#include "vm/SharedStencil.h"  // GCThingIndex
+
+namespace js {
+
+class Scope;
+
+namespace frontend {
+
+struct BytecodeEmitter;
+
+// A scope that introduces bindings.
+class EmitterScope : public Nestable<EmitterScope> {
+  // The cache of bound names that may be looked up in the
+  // scope. Initially populated as the set of names this scope binds. As
+  // names are looked up in enclosing scopes, they are cached on the
+  // current scope.
+  PooledMapPtr<NameLocationMap> nameCache_;
+
+  // If this scope's cache does not include free names, such as the
+  // global scope, the NameLocation to return.
+  mozilla::Maybe<NameLocation> fallbackFreeNameLocation_;
+
+  // True if there is a corresponding EnvironmentObject on the environment
+  // chain, false if all bindings are stored in frame slots on the stack.
+  bool hasEnvironment_;
+
+  // The number of enclosing environments. Used for error checking.
+  uint8_t environmentChainLength_;
+
+  // The next usable slot on the frame for not-closed over bindings.
+  //
+  // The initial frame slot when assigning slots to bindings is the
+  // enclosing scope's nextFrameSlot. For the first scope in a frame,
+  // the initial frame slot is 0.
+  uint32_t nextFrameSlot_;
+
+  // The index in the BytecodeEmitter's interned scope vector, otherwise
+  // ScopeNote::NoScopeIndex.
+  GCThingIndex scopeIndex_;
+
+  // If kind is Lexical, Catch, or With, the index in the BytecodeEmitter's
+  // block scope note list. Otherwise ScopeNote::NoScopeNote.
+  uint32_t noteIndex_;
+
+  MOZ_MUST_USE bool ensureCache(BytecodeEmitter* bce);
+
+  MOZ_MUST_USE bool checkSlotLimits(BytecodeEmitter* bce,
+                                    const ParserBindingIter& bi);
+
+  MOZ_MUST_USE bool checkEnvironmentChainLength(BytecodeEmitter* bce);
+
+  void updateFrameFixedSlots(BytecodeEmitter* bce, const ParserBindingIter& bi);
+
+  MOZ_MUST_USE bool putNameInCache(BytecodeEmitter* bce, const ParserAtom* name,
+                                   NameLocation loc);
+
+  mozilla::Maybe<NameLocation> lookupInCache(BytecodeEmitter* bce,
+                                             const ParserAtom* name);
+
+  EmitterScope* enclosing(BytecodeEmitter** bce) const;
+
+  mozilla::Maybe<ScopeIndex> enclosingScopeIndex(BytecodeEmitter* bce) const;
+
+  static bool nameCanBeFree(BytecodeEmitter* bce, const ParserAtom* name);
+
+  static NameLocation searchInEnclosingScope(JSAtom* name, Scope* scope,
+                                             uint8_t hops);
+  NameLocation searchAndCache(BytecodeEmitter* bce, const ParserAtom* name);
+
+  MOZ_MUST_USE bool internEmptyGlobalScopeAsBody(BytecodeEmitter* bce);
+
+  template <typename ScopeCreator>
+  MOZ_MUST_USE bool internScopeCreationData(BytecodeEmitter* bce,
+                                            ScopeCreator createScope);
+
+  template <typename ScopeCreator>
+  MOZ_MUST_USE bool internBodyScopeCreationData(BytecodeEmitter* bce,
+                                                ScopeCreator createScope);
+  MOZ_MUST_USE bool appendScopeNote(BytecodeEmitter* bce);
+
+  MOZ_MUST_USE bool clearFrameSlotRange(BytecodeEmitter* bce, JSOp opcode,
+                                        uint32_t slotStart,
+                                        uint32_t slotEnd) const;
+
+  MOZ_MUST_USE bool deadZoneFrameSlotRange(BytecodeEmitter* bce,
+                                           uint32_t slotStart,
+                                           uint32_t slotEnd) const {
+    return clearFrameSlotRange(bce, JSOp::Uninitialized, slotStart, slotEnd);
+  }
+
+ public:
+  explicit EmitterScope(BytecodeEmitter* bce);
+
+  void dump(BytecodeEmitter* bce);
+
+  MOZ_MUST_USE bool enterLexical(BytecodeEmitter* bce, ScopeKind kind,
+                                 LexicalScope::ParserData* bindings);
+  MOZ_MUST_USE bool enterNamedLambda(BytecodeEmitter* bce, FunctionBox* funbox);
+  MOZ_MUST_USE bool enterFunction(BytecodeEmitter* bce, FunctionBox* funbox);
+  MOZ_MUST_USE bool enterFunctionExtraBodyVar(BytecodeEmitter* bce,
+                                              FunctionBox* funbox);
+  MOZ_MUST_USE bool enterGlobal(BytecodeEmitter* bce,
+                                GlobalSharedContext* globalsc);
+  MOZ_MUST_USE bool enterEval(BytecodeEmitter* bce, EvalSharedContext* evalsc);
+  MOZ_MUST_USE bool enterModule(BytecodeEmitter* module,
+                                ModuleSharedContext* modulesc);
+  MOZ_MUST_USE bool enterWith(BytecodeEmitter* bce);
+  MOZ_MUST_USE bool deadZoneFrameSlots(BytecodeEmitter* bce) const;
+
+  MOZ_MUST_USE bool leave(BytecodeEmitter* bce, bool nonLocal = false);
+
+  GCThingIndex index() const {
+    MOZ_ASSERT(scopeIndex_ != ScopeNote::NoScopeIndex,
+               "Did you forget to intern a Scope?");
+    return scopeIndex_;
+  }
+
+  uint32_t noteIndex() const { return noteIndex_; }
+
+  AbstractScopePtr scope(const BytecodeEmitter* bce) const;
+  mozilla::Maybe<ScopeIndex> scopeIndex(const BytecodeEmitter* bce) const;
+
+  bool hasEnvironment() const { return hasEnvironment_; }
+
+  // The first frame slot used.
+  uint32_t frameSlotStart() const {
+    if (EmitterScope* inFrame = enclosingInFrame()) {
+      return inFrame->nextFrameSlot_;
+    }
+    return 0;
+  }
+
+  // The last frame slot used + 1.
+  uint32_t frameSlotEnd() const { return nextFrameSlot_; }
+
+  EmitterScope* enclosingInFrame() const {
+    return Nestable<EmitterScope>::enclosing();
+  }
+
+  NameLocation lookup(BytecodeEmitter* bce, const ParserAtom* name);
+
+  mozilla::Maybe<NameLocation> locationBoundInScope(const ParserAtom* name,
+                                                    EmitterScope* target);
+};
+
+} /* namespace frontend */
+} /* namespace js */
+
+#endif /* frontend_EmitterScope_h */