Address review comments.

Author: qiongsiwu

clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h

@@ -220,40 +220,33 @@ class DependencyScanningFilesystemSharedCache {
   CacheShard &getShardForFilename(StringRef Filename) const;
   CacheShard &getShardForUID(llvm::sys::fs::UniqueID UID) const;
 
-  struct InvalidEntryDiagInfo {
+  struct OutOfDateEntry {
     // A null terminated string that contains a path.
     const char *Path = nullptr;
 
-    enum class Type : unsigned char { NegativeCaching = 1, SizeChanged = 2 };
-
-    Type T;
-
+    struct NegativelyCachedInfo {};
     struct SizeChangedInfo {
       uint64_t CachedSize = 0;
       uint64_t ActualSize = 0;
     };
 
-    std::optional<SizeChangedInfo> SizeInfo;
+    std::variant<NegativelyCachedInfo, SizeChangedInfo> Info;
 
-    InvalidEntryDiagInfo(const char *Path) : Path(Path) {
-      T = Type::NegativeCaching;
-    }
+    OutOfDateEntry(const char *Path)
+        : Path(Path), Info(NegativelyCachedInfo{}) {}
 
-    InvalidEntryDiagInfo(const char *Path, uint64_t CachedSize,
-                         uint64_t ActualSize)
-        : Path(Path), SizeInfo({CachedSize, ActualSize}) {
-      T = Type::SizeChanged;
-    }
+    OutOfDateEntry(const char *Path, uint64_t CachedSize, uint64_t ActualSize)
+        : Path(Path), Info(SizeChangedInfo{CachedSize, ActualSize}) {}
   };
 
   /// Visits all cached entries and re-stat an entry using UnderlyingFS to check
-  /// if the cache contains invalid entries. An entry can be invalid for two
-  /// reasons:
+  /// if the cache contains out-of-date entries. An entry can be out-of-date for
+  /// two reasons:
   ///  1. The entry contains a stat error, indicating the file did not exist
   ///     in the cache, but the file exists on the UnderlyingFS.
   ///  2. The entry is associated with a file whose size is different from the
-  ///     actual size on the UnderlyingFS.
-  std::vector<InvalidEntryDiagInfo>
+  ///     size of the file on the same path on the UnderlyingFS.
+  std::vector<OutOfDateEntry>
   getInvalidEntryDiagInfo(llvm::vfs::FileSystem &UnderlyingFS) const;
 
 private:

clang/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp

@@ -107,11 +107,11 @@ DependencyScanningFilesystemSharedCache::getShardForUID(
   return CacheShards[Hash % NumShards];
 }
 
-std::vector<DependencyScanningFilesystemSharedCache::InvalidEntryDiagInfo>
+std::vector<DependencyScanningFilesystemSharedCache::OutOfDateEntry>
 DependencyScanningFilesystemSharedCache::getInvalidEntryDiagInfo(
     llvm::vfs::FileSystem &UnderlyingFS) const {
   // Iterate through all shards and look for cached stat errors.
-  std::vector<InvalidEntryDiagInfo> InvalidDiagInfo;
+  std::vector<OutOfDateEntry> InvalidDiagInfo;
   for (unsigned i = 0; i < NumShards; i++) {
     const CacheShard &Shard = CacheShards[i];
     std::lock_guard<std::mutex> LockGuard(Shard.CacheLock);

clang/unittests/Tooling/DependencyScanning/DependencyScanningFilesystemTest.cpp

@@ -226,7 +226,9 @@ TEST(DependencyScanningFilesystem, DiagnoseCachedFileSizeChange) {
 
   ASSERT_EQ(InvalidEntries.size(), 1u);
   ASSERT_STREQ("/path1.suffix", InvalidEntries[0].Path);
-  auto SizeInfo = InvalidEntries[0].SizeInfo;
+  auto SizeInfo = std::get_if<
+      DependencyScanningFilesystemSharedCache::OutOfDateEntry::SizeChangedInfo>(
+      &InvalidEntries[0].Info);
   ASSERT_TRUE(SizeInfo);
   ASSERT_EQ(SizeInfo->CachedSize, 0u);
   ASSERT_EQ(SizeInfo->ActualSize, 8u);