[clang][cli] Store InputKind in FrontendOptions

[jansvoboda11]

Summary

This patch stores the InputKind (parsed mainly from -x) to FrontendOptions. This is necessary for command line generation.

[jansvoboda11]

Fix typo in comment

[dexonsmith]

LGTM.

clang/include/clang/Frontend/FrontendOptions.h

ObjCMT_MigrateAll = (ObjCMT_Literals | ObjCMT_Subscripting |
                          ObjCMT_MigrateDecls | ObjCMT_PropertyDotSyntax)
   };
   unsigned ObjCMTAction = ObjCMT_None;
   std::string ObjCMTWhiteListPath;
 
   std::string MTMigrateDir;
   std::string ARCMTMigrateReportOut;
 
+  /// The input kind, either specified via -x argument or deduced from the input
+  /// file name.
+  InputKind DashX;
+
   /// The input files and their types.
   SmallVector<FrontendInputFile, 0> Inputs;
 
   /// When the input is a module map, the original module map file from which
   /// that map was inferred, if any (for umbrella modules).
   std::string OriginalModuleMap;
 
   /// The output file, if any.

clang/lib/Frontend/CompilerInvocation.cpp

static bool parseTestModuleFileExtensionArg(StringRef Arg,
   if (Args[1].getAsInteger(10, MajorVersion)) return true;
   if (Args[2].getAsInteger(10, MinorVersion)) return true;
   if (Args[3].getAsInteger(2, Hashed)) return true;
   if (Args.size() > 4)
     UserInfo = std::string(Args[4]);
   return false;
 }
 
-static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
-                                   DiagnosticsEngine &Diags,
-                                   bool &IsHeaderFile) {
+static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
+                              DiagnosticsEngine &Diags, bool &IsHeaderFile) {
+  unsigned NumErrorsBefore = Diags.getNumErrors();
+
   Opts.ProgramAction = frontend::ParseSyntaxOnly;
   if (const Arg *A = Args.getLastArg(OPT_Action_Group)) {
     switch (A->getOption().getID()) {
     default:
       llvm_unreachable("Invalid option in group!");
     case OPT_ast_list:
       Opts.ProgramAction = frontend::ASTDeclList; break;
     case OPT_ast_dump_all_EQ:
if (Opts.ProgramAction == frontend::GenerateModule &&
         IK.getFormat() == InputKind::Source) {
       IK = IK.withFormat(InputKind::ModuleMap);
       IsSystem = Opts.IsSystemModule;
     }
 
     Opts.Inputs.emplace_back(std::move(Inputs[i]), IK, IsSystem);
   }
 
-  return DashX;
+  Opts.DashX = DashX;
+
+  return Diags.getNumErrors() == NumErrorsBefore;
 }
 
 std::string CompilerInvocation::GetResourcesPath(const char *Argv0,
                                                  void *MainAddr) {
   std::string ClangExecutable =
       llvm::sys::fs::getMainExecutable(Argv0, MainAddr);
   return Driver::GetResourcesPath(ClangExecutable, CLANG_RESOURCE_DIR);
 }
bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
   ParseDependencyOutputArgs(Res.getDependencyOutputOpts(), Args);
   if (!Res.getDependencyOutputOpts().OutputFile.empty() &&
       Res.getDependencyOutputOpts().Targets.empty()) {
     Diags.Report(diag::err_fe_dependency_file_requires_MT);
     Success = false;
   }
   Success &= ParseDiagnosticArgs(Res.getDiagnosticOpts(), Args, &Diags,
                                  /*DefaultDiagColor=*/false);
-  // FIXME: We shouldn't have to pass the DashX option around here
-  InputKind DashX = ParseFrontendArgs(Res.getFrontendOpts(), Args, Diags,
-                                      LangOpts.IsHeaderFile);
+  Success &= ParseFrontendArgs(Res.getFrontendOpts(), Args, Diags,
+  // FIXME: We shouldn't have to pass the DashX option around here
+  InputKind DashX = Res.getFrontendOpts().DashX;
   ParseTargetArgs(Res.getTargetOpts(), Args, Diags);
   llvm::Triple T(Res.getTargetOpts().Triple);
   ParseHeaderSearchArgs(Res, Res.getHeaderSearchOpts(), Args, Diags,
                         Res.getFileSystemOpts().WorkingDir);
   if (DashX.getFormat() == InputKind::Precompiled ||
       DashX.getLanguage() == Language::LLVM_IR) {
     // ObjCAAutoRefCount and Sanitize LangOpts are used to setup the
     // PassManager in BackendUtil.cpp. They need to be initializd no matter