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diff --git a/js/src/ds/Nestable.h b/js/src/ds/Nestable.h
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+++ b/js/src/ds/Nestable.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 ds_Nestable_h
+#define ds_Nestable_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+
+namespace js {
+
+// A base class for nestable structures.
+template <typename Concrete>
+class MOZ_STACK_CLASS Nestable {
+  Concrete** stack_;
+  Concrete* enclosing_;
+
+ protected:
+  explicit Nestable(Concrete** stack) : stack_(stack), enclosing_(*stack) {
+    *stack_ = static_cast<Concrete*>(this);
+  }
+
+  // These method are protected. Some derived classes, such as ParseContext,
+  // do not expose the ability to walk the stack.
+  Concrete* enclosing() const { return enclosing_; }
+
+  template <typename Predicate /* (Concrete*) -> bool */>
+  static Concrete* findNearest(Concrete* it, Predicate predicate) {
+    while (it && !predicate(it)) {
+      it = it->enclosing();
+    }
+    return it;
+  }
+
+  template <typename T>
+  static T* findNearest(Concrete* it) {
+    while (it && !it->template is<T>()) {
+      it = it->enclosing();
+    }
+    return it ? &it->template as<T>() : nullptr;
+  }
+
+  template <typename T, typename Predicate /* (T*) -> bool */>
+  static T* findNearest(Concrete* it, Predicate predicate) {
+    while (it && (!it->template is<T>() || !predicate(&it->template as<T>()))) {
+      it = it->enclosing();
+    }
+    return it ? &it->template as<T>() : nullptr;
+  }
+
+ public:
+  ~Nestable() {
+    MOZ_ASSERT(*stack_ == static_cast<Concrete*>(this));
+    *stack_ = enclosing_;
+  }
+};
+
+}  // namespace js
+
+#endif /* ds_Nestable_h */