[clangd] Dont index Symbols with invalid source location

[kadircet]

Summary

After rL358098 clangd started to index redecls of implicit symbols, but
sometimes these decls lack the source location information which results in
undefined behaviors in clangd.

clang-tools-extra/clangd/index/SymbolCollector.cpp

bool SymbolCollector::handleDeclOccurence(
   if ((Roles & static_cast<unsigned>(index::SymbolRole::NameReference)))
     return true;
   // A declaration created for a friend declaration should not be used as the
   // canonical declaration in the index. Use OrigD instead, unless we've already
   // picked a replacement for D
   if (D->getFriendObjectKind() != Decl::FriendObjectKind::FOK_None)
     D = CanonicalDecls.try_emplace(D, ASTNode.OrigD).first->second;
   const NamedDecl *ND = dyn_cast<NamedDecl>(D);
-  if (!ND)
+  if (!ND || ND->getLocation().isInvalid())
     return true;
 
   // Mark D as referenced if this is a reference coming from the main file.
   // D may not be an interesting symbol, but it's cheaper to check at the end.
   auto &SM = ASTCtx->getSourceManager();
   auto SpellingLoc = SM.getSpellingLoc(Loc);
   if (Opts.CountReferences &&
       (Roles & static_cast<unsigned>(index::SymbolRole::Reference)) &&
if (!IsMainFileOnly && isIndexedForCodeCompletion(ND, Ctx))
     S.Flags |= Symbol::IndexedForCodeCompletion;
   if (isImplementationDetail(&ND))
     S.Flags |= Symbol::ImplementationDetail;
   if (!IsMainFileOnly)
     S.Flags |= Symbol::VisibleOutsideFile;
   S.SymInfo = index::getSymbolInfo(&ND);
   std::string FileURI;
   auto Loc = findNameLoc(&ND);
+  assert(Loc.isValid() && "Invalid source location for NamedDecl");
   // FIXME: use the result to filter out symbols.
   shouldIndexFile(SM, SM.getFileID(Loc), Opts, &FilesToIndexCache);
   if (auto DeclLoc =
           getTokenLocation(Loc, SM, Opts, ASTCtx->getLangOpts(), FileURI))
     S.CanonicalDeclaration = *DeclLoc;
 
   S.Origin = Opts.Origin;
   if (ND.getAvailability() == AR_Deprecated)

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

TEST_F(SymbolCollectorTest, CBuiltins) {
   // In C, printf in stdio.h is a redecl of an implicit builtin.
   const char *Header = R"(
     extern int printf(const char*, ...);
   )";
   runSymbolCollector(Header, /**/ "", {"-xc"});
   EXPECT_THAT(Symbols, Contains(QName("printf")));
 }
 
+TEST_F(SymbolCollectorTest, InvalidSourceLoc) {
+  const char *Header = R"(
+      void operator delete(void*)
+        __attribute__((__externally_visible__));)";
+  runSymbolCollector(Header, /**/ "");
+  EXPECT_THAT(Symbols, IsEmpty());
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang