[clangd] Fix a regression issue in local rename.

[hokein]

Summary

The regression is that we can't rename symbols in annonymous
namespaces.

[ilya-biryukov]

LGTM

clang-tools-extra/clangd/refactor/Rename.cpp

136

NIT: the comment seems to duplicate the code, maybe remove it?

clang-tools-extra/clangd/refactor/Rename.cpp

llvm::Optional<ReasonToReject> renameable(const Decl &RenameDecl,
   if (const auto *FD = llvm::dyn_cast<FunctionDecl>(&RenameDecl)) {
     if (FD->isOverloadedOperator())
       return ReasonToReject::UnsupportedSymbol;
   }
   // function-local symbols is safe to rename.
   if (RenameDecl.getParentFunctionOrMethod())
     return None;
 
+  // Check whether the symbol being rename is indexable.
+  auto &ASTCtx = RenameDecl.getASTContext();
+  bool MainFileIsHeader = isHeaderFile(MainFilePath, ASTCtx.getLangOpts());
+  bool DeclaredInMainFile =
+      isInsideMainFile(RenameDecl.getBeginLoc(), ASTCtx.getSourceManager());
+  bool IsMainFileOnly = true;
+  if (MainFileIsHeader)
+    // main file is a header, the symbol can't be main file only.
+    IsMainFileOnly = false;
+  else if (!DeclaredInMainFile)
+    IsMainFileOnly = false;
   bool IsIndexable =
       isa<NamedDecl>(RenameDecl) &&
       SymbolCollector::shouldCollectSymbol(
           cast<NamedDecl>(RenameDecl), RenameDecl.getASTContext(),
-          SymbolCollector::Options(), CrossFile);
+          SymbolCollector::Options(), IsMainFileOnly);
   if (!IsIndexable) // If the symbol is not indexable, we disallow rename.
     return ReasonToReject::NonIndexable;
 
   if (!CrossFile) {
-    auto &ASTCtx = RenameDecl.getASTContext();
-    const auto &SM = ASTCtx.getSourceManager();
-    bool MainFileIsHeader = isHeaderFile(MainFilePath, ASTCtx.getLangOpts());
-    bool DeclaredInMainFile = isInsideMainFile(RenameDecl.getBeginLoc(), SM);
-
     if (!DeclaredInMainFile)
       // We are sure the symbol is used externally, bail out early.
       return ReasonToReject::UsedOutsideFile;
 
     // If the symbol is declared in the main file (which is not a header), we
     // rename it.
     if (!MainFileIsHeader)
       return None;

clang-tools-extra/clangd/unittests/RenameTests.cpp

Case Cases[] = {
 
       {R"cpp(// disallow -- symbol is indexable and has other refs in index.
         void f() {
           Out^side s;
         }
       )cpp",
        "used outside main file", HeaderFile, Index},
 
-      {R"cpp(// disallow -- symbol is not indexable.
+      {R"cpp(// disallow -- symbol in annonymous namespace in header is not indexable.
         namespace {
         class Unin^dexable {};
         }
       )cpp",
        "not eligible for indexing", HeaderFile, Index},
 
+      {R"cpp(// allow -- symbol in annonymous namespace in non-header file is indexable.
+        namespace {
+        class [[F^oo]] {};
+        }
+      )cpp",
+       nullptr, !HeaderFile, Index},
+
       {R"cpp(// disallow -- namespace symbol isn't supported
         namespace n^s {}
       )cpp",
        "not a supported kind", HeaderFile, Index},
 
       {
           R"cpp(
          #define MACRO 1