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diff --git a/lldb/source/Plugins/ExpressionParser/Clang/CxxModuleHandler.h b/lldb/source/Plugins/ExpressionParser/Clang/CxxModuleHandler.h
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+++ b/lldb/source/Plugins/ExpressionParser/Clang/CxxModuleHandler.h
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+//===-- CxxModuleHandler.h --------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_SOURCE_PLUGINS_EXPRESSIONPARSER_CLANG_CXXMODULEHANDLER_H
+#define LLDB_SOURCE_PLUGINS_EXPRESSIONPARSER_CLANG_CXXMODULEHANDLER_H
+
+#include "clang/AST/ASTImporter.h"
+#include "clang/Sema/Sema.h"
+#include "llvm/ADT/StringSet.h"
+
+namespace lldb_private {
+
+/// Handles importing decls into an ASTContext with an attached C++ module.
+///
+/// This class searches a C++ module (which must be attached to the target
+/// ASTContext) for an equivalent decl to the one that should be imported.
+/// If the decl that is found in the module is a suitable replacement
+/// for the decl that should be imported, the module decl will be treated as
+/// the result of the import process.
+///
+/// If the Decl that should be imported is a template specialization
+/// that doesn't exist yet in the target ASTContext (e.g. `std::vector<int>`),
+/// then this class tries to create the template specialization in the target
+/// ASTContext. This is only possible if the CxxModuleHandler can determine
+/// that instantiating this template is safe to do, e.g. because the target
+/// decl is a container class from the STL.
+class CxxModuleHandler {
+  /// The ASTImporter that should be used to import any Decls which aren't
+  /// directly handled by this class itself.
+  clang::ASTImporter *m_importer = nullptr;
+
+  /// The Sema instance of the target ASTContext.
+  clang::Sema *m_sema = nullptr;
+
+  /// List of template names this class currently supports. These are the
+  /// template names inside the 'std' namespace such as 'vector' or 'list'.
+  llvm::StringSet<> m_supported_templates;
+
+  /// Tries to manually instantiate the given foreign template in the target
+  /// context (designated by m_sema).
+  llvm::Optional<clang::Decl *> tryInstantiateStdTemplate(clang::Decl *d);
+
+public:
+  CxxModuleHandler() = default;
+  CxxModuleHandler(clang::ASTImporter &importer, clang::ASTContext *target);
+
+  /// Attempts to import the given decl into the target ASTContext by
+  /// deserializing it from the 'std' module. This function returns a Decl if a
+  /// Decl has been deserialized from the 'std' module. Otherwise this function
+  /// returns nothing.
+  llvm::Optional<clang::Decl *> Import(clang::Decl *d);
+
+  /// Returns true iff this instance is capable of importing any declarations
+  /// in the target ASTContext.
+  bool isValid() const { return m_sema != nullptr; }
+};
+
+} // namespace lldb_private
+
+#endif // LLDB_SOURCE_PLUGINS_EXPRESSIONPARSER_CLANG_CXXMODULEHANDLER_H