[clang-refactor] Get rid of OccurrencesFinder in RenamingAction, NFC

[hokein]

Summary

The OccurrencesFinder is only used in RenameOccurrences to find symbol
occurrences, there is no need to inherit RefactoringRule.

Replace it with a single utility function to avoid code misleading.

[sammccall]

(This seems trivial enough to submit without review FWIW)

lib/Tooling/Refactoring/Rename/RenamingAction.cpp

 
 using namespace llvm;
 
 namespace clang {
 namespace tooling {
 
 namespace {
 
-class OccurrenceFinder final : public FindSymbolOccurrencesRefactoringRule {
-public:
-  OccurrenceFinder(const NamedDecl *ND) : ND(ND) {}
-
-  Expected<SymbolOccurrences>
-  findSymbolOccurrences(RefactoringRuleContext &Context) override {
-    std::vector<std::string> USRs =
-        getUSRsForDeclaration(ND, Context.getASTContext());
-    std::string PrevName = ND->getNameAsString();
-    return getOccurrencesOfUSRs(
-        USRs, PrevName, Context.getASTContext().getTranslationUnitDecl());
-  }
+findSymbolOccurrences(const NamedDecl *ND, RefactoringRuleContext &Context) {
+  return getOccurrencesOfUSRs(USRs, PrevName,
+                              Context.getASTContext().getTranslationUnitDecl());
 
-private:
-  const NamedDecl *ND;
-};
-
 } // end anonymous namespace
 
 const RefactoringDescriptor &RenameOccurrences::describe() {
   static const RefactoringDescriptor Descriptor = {
       "local-rename",
       "Rename",
       "Finds and renames symbols in code with no indexer support",
   };
if (!ND)
     return Context.createDiagnosticError(
         SelectionRange.getBegin(), diag::err_refactor_selection_no_symbol);
   return RenameOccurrences(getCanonicalSymbolDeclaration(ND),
                            std::move(NewName));
 }
 
 Expected<AtomicChanges>
 RenameOccurrences::createSourceReplacements(RefactoringRuleContext &Context) {
-  Expected<SymbolOccurrences> Occurrences =
-      OccurrenceFinder(ND).findSymbolOccurrences(Context);
+  Expected<SymbolOccurrences> Occurrences = findSymbolOccurrences(ND, Context);
   if (!Occurrences)
     return Occurrences.takeError();
   // FIXME: Verify that the new name is valid.
   SymbolName Name(NewName);
   return createRenameReplacements(
       *Occurrences, Context.getASTContext().getSourceManager(), Name);
 }