Merge pull request swiftlang#34175 from slavapestov/disable-parse-time-lookup

Frontend: Disable parse-time name lookup by default

Author: slavapestov

lib/Frontend/CompilerInvocation.cpp

@@ -427,7 +427,7 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   Opts.DisableParserLookup |= Args.hasFlag(OPT_disable_parser_lookup,
                                            OPT_enable_parser_lookup,
-                                           /*default*/ false);
+                                           /*default*/ true);
   Opts.EnableNewOperatorLookup = Args.hasFlag(OPT_enable_new_operator_lookup,
                                               OPT_disable_new_operator_lookup,
                                               /*default*/ false);