Add interface for lookup up of externally stored type descriptors

include/swift/RemoteInspection/DescriptorFinder.h

@@ -0,0 +1,53 @@
+//===--------------- DescriptorFinder.h -------------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_REFLECTION_DESCRIPTOR_FINDER_H
+#define SWIFT_REFLECTION_DESCRIPTOR_FINDER_H
+
+#include "llvm/ADT/StringRef.h"
+
+namespace swift {
+namespace reflection {
+
+class TypeRef;
+
+/// An abstract interface for a builtin type descriptor.
+struct BuiltinTypeDescriptorBase {
+  const uint32_t Size;
+  const uint32_t Alignment;
+  const uint32_t Stride;
+  const uint32_t NumExtraInhabitants;
+  const bool IsBitwiseTakable;
+
+  BuiltinTypeDescriptorBase(uint32_t Size, uint32_t Alignment, uint32_t Stride,
+                            uint32_t NumExtraInhabitants, bool IsBitwiseTakable)
+      : Size(Size), Alignment(Alignment), Stride(Stride),
+        NumExtraInhabitants(NumExtraInhabitants),
+        IsBitwiseTakable(IsBitwiseTakable) {}
+
+  virtual ~BuiltinTypeDescriptorBase(){};
+
+  virtual llvm::StringRef getMangledTypeName() = 0;
+};
+
+/// Interface for finding type descriptors. Implementors may provide descriptors
+/// that live inside or outside reflection metadata.
+struct DescriptorFinder {
+  virtual ~DescriptorFinder(){};
+
+  virtual std::unique_ptr<BuiltinTypeDescriptorBase>
+  getBuiltinTypeDescriptor(const TypeRef *TR) = 0;
+};
+
+} // namespace reflection
+} // namespace swift
+#endif

include/swift/RemoteInspection/ReflectionContext.h

@@ -30,6 +30,7 @@
 #include "swift/Concurrency/Actor.h"
 #include "swift/Remote/MemoryReader.h"
 #include "swift/Remote/MetadataReader.h"
+#include "swift/RemoteInspection/DescriptorFinder.h"
 #include "swift/RemoteInspection/GenericMetadataCacheEntry.h"
 #include "swift/RemoteInspection/Records.h"
 #include "swift/RemoteInspection/RuntimeInternals.h"
@@ -214,8 +215,9 @@ class ReflectionContext
 
   explicit ReflectionContext(
       std::shared_ptr<MemoryReader> reader,
-      remote::ExternalTypeRefCache *externalCache = nullptr)
-      : super(std::move(reader), *this, externalCache) {}
+      remote::ExternalTypeRefCache *externalCache = nullptr,
+      reflection::DescriptorFinder *descriptorFinder = nullptr)
+      : super(std::move(reader), *this, externalCache, descriptorFinder) {}
 
   ReflectionContext(const ReflectionContext &other) = delete;
   ReflectionContext &operator=(const ReflectionContext &other) = delete;

include/swift/RemoteInspection/TypeLowering.h

@@ -23,6 +23,7 @@
 #include "llvm/Support/Casting.h"
 #include "swift/Remote/MetadataReader.h"
 #include "swift/Remote/TypeInfoProvider.h"
+#include "swift/RemoteInspection/DescriptorFinder.h"
 
 #include <memory>
 
@@ -174,7 +175,7 @@ class BuiltinTypeInfo : public TypeInfo {
 
 public:
   explicit BuiltinTypeInfo(TypeRefBuilder &builder,
-                           RemoteRef<BuiltinTypeDescriptor> descriptor);
+                           BuiltinTypeDescriptorBase &descriptor);
 
   /// Construct an empty builtin type info.
   BuiltinTypeInfo()