[CAS/OnDiskHashMappedTrie] Guard the implementation using LLVM_ENABLE_ONDISK_CAS

Guard the implementation using preprocessor guards that check `LLVM_ENABLE_ONDISK_CAS` but without putting
that macro in the `llvm/cas` header.

Author: akyrtzi

llvm/lib/CAS/OnDiskHashMappedTrie.cpp

@@ -21,6 +21,8 @@
 using namespace llvm;
 using namespace llvm::cas;
 
+#if LLVM_ENABLE_ONDISK_CAS
+
 static_assert(sizeof(size_t) == sizeof(uint64_t), "64-bit only");
 static_assert(sizeof(std::atomic<int64_t>) == sizeof(uint64_t),
               "Requires lock-free 64-bit atomics");
@@ -1115,14 +1117,6 @@ Expected<OnDiskHashMappedTrie> OnDiskHashMappedTrie::create(
   return OnDiskHashMappedTrie(std::make_unique<ImplType>(std::move(Impl)));
 }
 
-OnDiskHashMappedTrie::OnDiskHashMappedTrie(std::unique_ptr<ImplType> Impl)
-    : Impl(std::move(Impl)) {}
-OnDiskHashMappedTrie::OnDiskHashMappedTrie(OnDiskHashMappedTrie &&RHS) =
-    default;
-OnDiskHashMappedTrie &
-OnDiskHashMappedTrie::operator=(OnDiskHashMappedTrie &&RHS) = default;
-OnDiskHashMappedTrie::~OnDiskHashMappedTrie() = default;
-
 //===----------------------------------------------------------------------===//
 // DataAllocator data structures.
 //===----------------------------------------------------------------------===//
@@ -1266,6 +1260,68 @@ const char *OnDiskDataAllocator::beginData(FileOffset Offset) const {
 
 OnDiskDataAllocator::OnDiskDataAllocator(std::unique_ptr<ImplType> Impl)
     : Impl(std::move(Impl)) {}
+
+#else // !LLVM_ENABLE_ONDISK_CAS
+
+struct OnDiskHashMappedTrie::ImplType {};
+
+Expected<OnDiskHashMappedTrie> OnDiskHashMappedTrie::create(
+    const Twine &PathTwine, const Twine &TrieNameTwine, size_t NumHashBits,
+    uint64_t DataSize, uint64_t MaxFileSize,
+    Optional<uint64_t> NewFileInitialSize, Optional<size_t> NewTableNumRootBits,
+    Optional<size_t> NewTableNumSubtrieBits) {
+  llvm_unreachable("not supported");
+}
+
+OnDiskHashMappedTrie::pointer
+OnDiskHashMappedTrie::insertLazy(const_pointer Hint, ArrayRef<uint8_t> Hash,
+                                 LazyInsertOnConstructCB OnConstruct,
+                                 LazyInsertOnLeakCB OnLeak) {
+  llvm_unreachable("not supported");
+}
+
+OnDiskHashMappedTrie::const_pointer
+OnDiskHashMappedTrie::recoverFromFileOffset(FileOffset Offset) const {
+  llvm_unreachable("not supported");
+}
+
+OnDiskHashMappedTrie::const_pointer
+OnDiskHashMappedTrie::find(ArrayRef<uint8_t> Hash) const {
+  llvm_unreachable("not supported");
+}
+
+void OnDiskHashMappedTrie::print(
+    raw_ostream &OS, function_ref<void(ArrayRef<char>)> PrintRecordData) const {
+  llvm_unreachable("not supported");
+}
+
+struct OnDiskDataAllocator::ImplType {};
+
+Expected<OnDiskDataAllocator>
+OnDiskDataAllocator::create(const Twine &PathTwine, const Twine &TableNameTwine,
+                            uint64_t MaxFileSize,
+                            Optional<uint64_t> NewFileInitialSize) {
+  llvm_unreachable("not supported");
+}
+
+OnDiskDataAllocator::pointer OnDiskDataAllocator::allocate(size_t Size) {
+  llvm_unreachable("not supported");
+}
+
+const char *OnDiskDataAllocator::beginData(FileOffset Offset) const {
+  llvm_unreachable("not supported");
+}
+
+#endif // LLVM_ENABLE_ONDISK_CAS
+
+OnDiskHashMappedTrie::OnDiskHashMappedTrie(std::unique_ptr<ImplType> Impl)
+    : Impl(std::move(Impl)) {}
+OnDiskHashMappedTrie::OnDiskHashMappedTrie(OnDiskHashMappedTrie &&RHS) =
+    default;
+OnDiskHashMappedTrie &
+OnDiskHashMappedTrie::operator=(OnDiskHashMappedTrie &&RHS) = default;
+OnDiskHashMappedTrie::~OnDiskHashMappedTrie() = default;
+
 OnDiskDataAllocator::OnDiskDataAllocator(OnDiskDataAllocator &&RHS) = default;
 OnDiskDataAllocator &
 OnDiskDataAllocator::operator=(OnDiskDataAllocator &&RHS) = default;