[Driver] Don't try to spell check unsupported options

[bogner]

Summary

We currently spell check options that are listed as unsupported, but
this doesn't make much sense. If an option is explicitly unsupported
why would one that's spelled similarly be useful?

It looks like the reason this was added was that we explicitly mark
all --something flags as Unsupported rather than just leaving them
undefined and treating them as unknown. Drop that handling so that we
don't regress on things like misspelling --help.

[MaskRay]

Looks great! Nice example of fixing a problem by deleting code.

We've had def _ : Joined<"--"> since commit 46fffee081b583a617fa94397b0c758bdf3a4a80 (2009) when TableGen based options were introduced.

Due to it, the error messages are slightly different, but I agree that it is not a meaningful difference:

% fclang -qqq -c a.c
clang: error: unknown argument: '-qqq'
% fclang --qqq -c a.c
clang: error: unsupported option '--qqq'

clang/include/clang/Driver/Options.td

 def _undefine_macro : Separate<["--"], "undefine-macro">, Alias<U>;
 def _unsigned_char : Flag<["--"], "unsigned-char">, Alias<funsigned_char>;
 def _user_dependencies : Flag<["--"], "user-dependencies">, Alias<MM>;
 def _verbose : Flag<["--"], "verbose">, Alias<v>;
 def _warn__EQ : Joined<["--"], "warn-=">, Alias<W_Joined>;
 def _warn_ : Joined<["--"], "warn-">, Alias<W_Joined>;
 def _write_dependencies : Flag<["--"], "write-dependencies">, Alias<MD>;
 def _write_user_dependencies : Flag<["--"], "write-user-dependencies">, Alias<MMD>;
-def _ : Joined<["--"], "">, Flags<[Unsupported]>;
 
 // Hexagon feature flags.
 let Flags = [TargetSpecific] in {
 def mieee_rnd_near : Flag<["-"], "mieee-rnd-near">,
   Group<m_hexagon_Features_Group>;
 def mv5 : Flag<["-"], "mv5">, Group<m_hexagon_Features_Group>, Alias<mcpu_EQ>,
   AliasArgs<["hexagonv5"]>;
 def mv55 : Flag<["-"], "mv55">, Group<m_hexagon_Features_Group>,

clang/lib/Driver/Driver.cpp

if (MissingArgCount) {
     ContainsError |=
         Diags.getDiagnosticLevel(diag::err_drv_missing_argument,
                                  SourceLocation()) > DiagnosticsEngine::Warning;
   }
 
   // Check for unsupported options.
   for (const Arg *A : Args) {
     if (A->getOption().hasFlag(options::Unsupported)) {
-      unsigned DiagID;
-      auto ArgString = A->getAsString(Args);
-      std::string Nearest;
-      if (getOpts().findNearest(
-            ArgString, Nearest, IncludedFlagsBitmask,
-            ExcludedFlagsBitmask | options::Unsupported) > 1) {
-        DiagID = diag::err_drv_unsupported_opt;
-        Diag(DiagID) << ArgString;
-      } else {
-        DiagID = diag::err_drv_unsupported_opt_with_suggestion;
-        Diag(DiagID) << ArgString << Nearest;
-      }
-      ContainsError |= Diags.getDiagnosticLevel(DiagID, SourceLocation()) >
+      Diag(diag::err_drv_unsupported_opt) << A->getAsString(Args);
+      ContainsError |= Diags.getDiagnosticLevel(diag::err_drv_unsupported_opt,
+                                                SourceLocation()) >
                        DiagnosticsEngine::Warning;
       continue;
     }
 
     // Warn about -mcpu= without an argument.
     if (A->getOption().matches(options::OPT_mcpu_EQ) && A->containsValue("")) {
       Diag(diag::warn_drv_empty_joined_argument) << A->getAsString(Args);
       ContainsError |= Diags.getDiagnosticLevel(

clang/test/Driver/unsupported-option.c

 // RUN: not %clang %s --hedonism -### 2>&1 | \
 // RUN: FileCheck %s
-// CHECK: error: unsupported option '--hedonism'
+// CHECK: error: unknown argument: '--hedonism'
 
 // RUN: not %clang %s --hell -### 2>&1 | \
 // RUN: FileCheck %s --check-prefix=DID-YOU-MEAN
-// DID-YOU-MEAN: error: unsupported option '--hell'; did you mean '--help'?
+// DID-YOU-MEAN: error: unknown argument '--hell'; did you mean '--help'?
 
 // RUN: not %clang --target=powerpc-ibm-aix %s -mlong-double-128 2>&1 | \
 // RUN: FileCheck %s --check-prefix=AIX-LONGDOUBLE128-ERR
 // AIX-LONGDOUBLE128-ERR: error: unsupported option '-mlong-double-128' for target 'powerpc-ibm-aix'
 
 // RUN: not %clang --target=powerpc64-ibm-aix %s -mlong-double-128 2>&1 | \
 // RUN: FileCheck %s --check-prefix=AIX64-LONGDOUBLE128-ERR
 // AIX64-LONGDOUBLE128-ERR: error: unsupported option '-mlong-double-128' for target 'powerpc64-ibm-aix'
 
 // RUN: not %clang -fprofile-sample-use=code.prof --target=powerpc-ibm-aix %s 2>&1 | \
 // RUN: FileCheck %s --check-prefix=AIX-PROFILE-SAMPLE
 // AIX-PROFILE-SAMPLE: error: unsupported option '-fprofile-sample-use=' for target

flang/test/Driver/driver-version.f90

 
 ! RUN: %flang --version 2>&1 | FileCheck %s --check-prefix=VERSION
 ! RUN: not %flang --versions 2>&1 | FileCheck %s --check-prefix=ERROR
 ! RUN: %flang_fc1 -version 2>&1 | FileCheck %s --check-prefix=VERSION-FC1
 ! RUN: not %flang_fc1 --version 2>&1 | FileCheck %s --check-prefix=ERROR-FC1
 
 ! VERSION: flang-new version
 ! VERSION-NEXT: Target:
 ! VERSION-NEXT: Thread model:
 ! VERSION-NEXT: InstalledDir:
 
-! ERROR: flang-new: error: unsupported option '--versions'; did you mean '--version'?
+! ERROR: flang-new: error: unknown argument '--versions'; did you mean '--version'?
 
 ! VERSION-FC1: LLVM version
 
 ! ERROR-FC1: error: unknown argument '--version'; did you mean '-version'?