[clang-tools-extra] [clang-tidy][NFC] Do less unnecessary work in `NoLintDirectiveHandler` (PR #147553)

[Baranov Victor via cfe-commits]

================
@@ -349,46 +369,21 @@ bool NoLintDirectiveHandler::Impl::diagHasNoLint(
     return false;
 
   // Do we have cached NOLINT block locations for this file?
-  if (Cache.count(*FileName) == 0)
+  if (!Cache.contains(*FileName))
     // Warning: heavy operation - need to read entire file.
     generateCache(SrcMgr, *FileName, File, *Buffer, NoLintErrors);
 
   return withinNoLintBlock(Cache[*FileName], Pos, DiagName);
 }
 
-// Construct a [clang-tidy-nolint] diagnostic to do with the unmatched
-// NOLINT(BEGIN/END) pair.
-static tooling::Diagnostic makeNoLintError(const SourceManager &SrcMgr,
-                                           FileID File,
-                                           const NoLintToken &NoLint) {
-  tooling::Diagnostic Error;
-  Error.DiagLevel = tooling::Diagnostic::Error;
-  Error.DiagnosticName = "clang-tidy-nolint";
-  StringRef Message =
-      (NoLint.Type == NoLintType::NoLintBegin)
-          ? ("unmatched 'NOLINTBEGIN' comment without a subsequent 'NOLINT"
-             "END' comment")
-          : ("unmatched 'NOLINTEND' comment without a previous 'NOLINT"
-             "BEGIN' comment");
-  SourceLocation Loc = SrcMgr.getComposedLoc(File, NoLint.Pos);
-  Error.Message = tooling::DiagnosticMessage(Message, SrcMgr, Loc);
-  return Error;
-}
-
 // Find all NOLINT(BEGIN/END) blocks in a file and store in the cache.
 void NoLintDirectiveHandler::Impl::generateCache(
     const SourceManager &SrcMgr, StringRef FileName, FileID File,
     StringRef Buffer, SmallVectorImpl<tooling::Diagnostic> &NoLintErrors) {
-  // Read entire file to get all NOLINTs.
-  SmallVector<NoLintToken> NoLints = getNoLints(Buffer);
-
-  // Match each BEGIN with its corresponding END.
-  SmallVector<NoLintToken> UnmatchedTokens;
-  Cache[FileName] = formNoLintBlocks(std::move(NoLints), UnmatchedTokens);
-
-  // Raise error for any BEGIN/END left over.
-  for (const NoLintToken &NoLint : UnmatchedTokens)
-    NoLintErrors.emplace_back(makeNoLintError(SrcMgr, File, NoLint));
----------------
vbvictor wrote:

Why these lines are deleted?

https://github.com/llvm/llvm-project/pull/147553