Use SM.isWrittenInMainFile; suppress -Werror in preamble

SM.isWrittenInMainFile is to work around preamble bug: spurious err_pp_unterminated_conditional with circular #include

src/clang_complete.cc

@@ -209,7 +209,7 @@ class StoreDiags : public DiagnosticConsumer {
     if (!L.isValid()) return;
     const SourceManager &SM = Info.getSourceManager();
     StringRef Filename = SM.getFilename(Info.getLocation());
-    bool concerned = IsConcerned(SM, Info.getLocation());
+    bool concerned = SM.isWrittenInMainFile(L);
     auto fillDiagBase = [&](DiagBase &d) {
       llvm::SmallString<64> Message;
       Info.FormatDiagnostic(Message);
@@ -303,6 +303,11 @@ void BuildPreamble(CompletionSession &session, CompilerInvocation &CI,
   auto Bounds = ComputePreambleBounds(*CI.getLangOpts(), Buf.get(), 0);
   if (OldP && OldP->Preamble.CanReuse(CI, Buf.get(), Bounds, FS.get()))
     return;
+  // -Werror makes warnings issued as errors, which stops parsing
+  // prematurely because of -ferror-limit=. This also works around the issue
+  // of -Werror + -Wunused-parameter in interaction with SkipFunctionBodies.
+  auto &Ws = CI.getDiagnosticOpts().Warnings;
+  Ws.erase(std::remove(Ws.begin(), Ws.end(), "error"), Ws.end());
   CI.getDiagnosticOpts().IgnoreWarnings = false;
   CI.getFrontendOpts().SkipFunctionBodies = true;
   CI.getLangOpts()->CommentOpts.ParseAllComments = g_config->index.comments > 1;

src/indexer.cc

@@ -707,7 +707,7 @@ class IndexDataConsumer : public index::IndexDataConsumer {
       if (!db)
         return true;
       param.SeenFile(*FE);
-      if (!SM.isInMainFile(R.getBegin()))
+      if (!SM.isWrittenInMainFile(R.getBegin()))
         lid = GetFileLID(db, SM, *FE);
     } else {
       db = param.ConsumeFile(*FE);