[clangd] NFC: Cleanup IncludeCleaner API

[kbobyrev]

Summary

Make a further improvement to decrease verbosity of the API: ASTContext
provides SourceManager access.

[sammccall]

Not sure how I missed this patch, sorry!

clang-tools-extra/clangd/IncludeCleaner.h

 /// - If \p Tokens is not nullptr, we also examine all identifier tokens in the
 ///   file in case they reference macros macros.
 /// We use this to compute unused headers, so we:
 ///
 /// - cover the whole file in a single traversal for efficiency
 /// - don't attempt to describe where symbols were referenced from in
 ///   ambiguous cases (e.g. implicitly used symbols, multiple declarations)
 /// - err on the side of reporting all possible locations
-ReferencedLocations findReferencedLocations(const SourceManager &SM,
-                                            ASTContext &Ctx, Preprocessor &PP,
+ReferencedLocations findReferencedLocations(ASTContext &Ctx, Preprocessor &PP,
                                             const syntax::TokenBuffer *Tokens);
 ReferencedLocations findReferencedLocations(ParsedAST &AST);
 
 struct ReferencedFiles {
   llvm::DenseSet<FileID> User;
   llvm::DenseSet<tooling::stdlib::Header> Stdlib;
 };
 

clang-tools-extra/clangd/IncludeCleaner.cpp

for (const FileEntry *FE = SM.getFileEntryForID(ID); ID != SM.getMainFileID();
     // on its includer.
     ID = SM.getFileID(SM.getIncludeLoc(ID));
   }
   return ID;
 }
 
 } // namespace
 
-ReferencedLocations findReferencedLocations(const SourceManager &SM,
-                                            ASTContext &Ctx, Preprocessor &PP,
+ReferencedLocations findReferencedLocations(ASTContext &Ctx, Preprocessor &PP,
                                             const syntax::TokenBuffer *Tokens) {
   trace::Span Tracer("IncludeCleaner::findReferencedLocations");
   ReferencedLocations Result;
+  const auto &SM = Ctx.getSourceManager();
   ReferencedLocationCrawler Crawler(Result, SM);
   Crawler.TraverseAST(Ctx);
   if (Tokens)
     findReferencedMacros(SM, PP, Tokens, Result);
   return Result;
 }
 
 ReferencedLocations findReferencedLocations(ParsedAST &AST) {
-  return findReferencedLocations(AST.getSourceManager(), AST.getASTContext(),
-                                 AST.getPreprocessor(), &AST.getTokens());
+  return findReferencedLocations(AST.getASTContext(), AST.getPreprocessor(),
+                                 &AST.getTokens());
 }
 
 ReferencedFiles
 findReferencedFiles(const ReferencedLocations &Locs, const SourceManager &SM,
                     llvm::function_ref<FileID(FileID)> HeaderResponsible) {
   std::vector<SourceLocation> Sorted{Locs.User.begin(), Locs.User.end()};
   llvm::sort(Sorted); // Group by FileID.
   ReferencedFilesBuilder Builder(SM);