[serialization] Add a trivial Swift module loader.

Currently, the Swift module loader just looks for a .sm file, verifies the
signature "SMod", and produces an empty DeclContext.

Swift SVN r5126

include/swift/Serialization/SerializedModuleLoader.h

@@ -0,0 +1,58 @@
+//===--- SerializedModuleLoader.h - Import Swift modules --------*- c++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_SERIALIZATION_MODULELOADER_H
+#define SWIFT_SERIALIZATION_MODULELOADER_H
+
+#include "swift/AST/ModuleLoader.h"
+
+namespace swift {
+
+class ASTContext;
+class Module;
+  
+/// \brief Imports serialized Swift modules into an ASTContext.
+class SerializedModuleLoader : public ModuleLoader {
+private:
+  ASTContext &Ctx;
+
+  explicit SerializedModuleLoader(ASTContext &ctx) : Ctx(ctx) {}
+
+public:
+  /// \brief Create a new importer that can load serialized Swift modules
+  /// into the given ASTContext.
+  static SerializedModuleLoader *create(ASTContext &ctx) {
+    return new SerializedModuleLoader(ctx);
+  }
+
+  SerializedModuleLoader(const SerializedModuleLoader &) = delete;
+  SerializedModuleLoader(SerializedModuleLoader &&) = delete;
+  SerializedModuleLoader &operator=(const SerializedModuleLoader &) = delete;
+  SerializedModuleLoader &operator=(SerializedModuleLoader &&) = delete;
+
+  /// \brief Import a module with the given module path.
+  ///
+  /// \param importLoc The location of the 'import' keyword.
+  ///
+  /// \param path A sequence of (identifier, location) pairs that denote
+  /// the dotted module name to load, e.g., AppKit.NSWindow.
+  ///
+  /// \returns the module referenced, if it could be loaded. Otherwise,
+  /// emits a diagnostic and returns NULL.
+  virtual Module *
+  loadModule(SourceLoc importLoc,
+             ArrayRef<std::pair<Identifier, SourceLoc>> path) override;
+};
+
+}
+
+#endif