[llvm] [CommandLine] Better report unknown subcommands (PR #74811)

[James Henderson via llvm-commits]

================
@@ -1687,21 +1708,35 @@ bool CommandLineParser::ParseCommandLineOptions(int argc,
     }
 
     if (!Handler) {
-      if (SinkOpts.empty()) {
-        *Errs << ProgramName << ": Unknown command line argument '" << argv[i]
-              << "'.  Try: '" << argv[0] << " --help'\n";
-
-        if (NearestHandler) {
-          // If we know a near match, report it as well.
-          *Errs << ProgramName << ": Did you mean '"
-                << PrintArg(NearestHandlerString, 0) << "'?\n";
-        }
-
-        ErrorParsing = true;
-      } else {
+      if (!SinkOpts.empty()) {
         for (Option *SinkOpt : SinkOpts)
           SinkOpt->addOccurrence(i, "", StringRef(argv[i]));
+        continue;
       }
+
+      auto reportUnknownArgument = [&](bool IsArg,
----------------
jh7370 wrote:

Nit: I think the LLVM consensus is that lambdas are objects, not functions, so should be named with upper-case, i.e. `ReportUnknownArgument`.

https://github.com/llvm/llvm-project/pull/74811