[lld/mac] Implement basic typo correction for flags

[thakis]

Summary

Also use "unknown flag 'flag'" instead of "unknown flag: flag" for
consistency with the other ports.

[hans]

lld/MachO/DriverUtils.cpp

78

i probably would have kept opt::Arg here, but i guess it's a personal preference

lld/test/MachO/driver.test

1

nit: blank line after run line is common (or am i just imagining this?)

[thakis]

Thanks! Landing.

lld/MachO/DriverUtils.cpp

opt::InputArgList MachOOptTable::parse(ArrayRef<const char *> argv) {
 
   opt::InputArgList args = ParseArgs(vec, missingIndex, missingCount);
 
   if (missingCount)
     error(Twine(args.getArgString(missingIndex)) + ": missing argument");
 
   handleColorDiagnostics(args);
 
-  for (opt::Arg *arg : args.filtered(OPT_UNKNOWN))
-    error("unknown argument: " + arg->getSpelling());
+  for (auto *arg : args.filtered(OPT_UNKNOWN)) {
+    std::string nearest;
+    if (findNearest(arg->getAsString(args), nearest) > 1)
+      error("unknown argument '" + arg->getAsString(args) + "'");
+    else
+      error("unknown argument '" + arg->getAsString(args) +
+            "', did you mean '" + nearest + "'");
+  }
   return args;
 }
 
 void MachOOptTable::printHelp(const char *argv0, bool showHidden) const {
   PrintHelp(lld::outs(), (std::string(argv0) + " [options] file...").c_str(),
             "LLVM Linker", showHidden);
   lld::outs() << "\n";
 }

lld/test/MachO/color-diagnostics.test

 # Windows command prompt doesn't support ANSI escape sequences.
 # REQUIRES: shell
 
 # RUN: not %lld -xyz --color-diagnostics /nosuchfile 2>&1 \
 # RUN:   | FileCheck -check-prefix=COLOR %s
 # RUN: not %lld -xyz --color-diagnostics=always /nosuchfile 2>&1 \
 # RUN:   | FileCheck -check-prefix=COLOR %s
 
-# COLOR: {{lld: .\[0;31merror: .\[0munknown argument: -xyz}}
+# COLOR: {{lld: .\[0;31merror: .\[0munknown argument '-xyz'}}
 # COLOR: {{lld: .\[0;31merror: .\[0mcannot open /nosuchfile}}
 
 # RUN: not %lld --color-diagnostics=foobar 2>&1 | FileCheck -check-prefix=ERR %s
 # ERR: unknown option: --color-diagnostics=foobar
 
 # RUN: not %lld /nosuchfile 2>&1 | FileCheck -check-prefix=NOCOLOR %s
 # RUN: not %lld --color-diagnostics=never /nosuchfile 2>&1 \
 # RUN:   | FileCheck -check-prefix=NOCOLOR %s
 # RUN: not %lld --color-diagnostics=always --no-color-diagnostics \
 # RUN:   /nosuchfile 2>&1 | FileCheck -check-prefix=NOCOLOR %s
 
 # NOCOLOR: lld: error: cannot open /nosuchfile

lld/test/MachO/driver.test

+# RUN: not %lld ---help 2>&1 | FileCheck -check-prefix=SPELLHELP %s
+SPELLHELP: error: unknown argument '---help', did you mean '--help'
+# FIXME: This should say "no input files" instead
+SPELLHELP: error: undefined symbol: _main

lld/test/MachO/silent-ignore.test

 RUN: %lld -v \
 RUN:   -demangle \
 RUN:   -dynamic \
 RUN:   -no_deduplicate \
 RUN:   -lto_library /lib/foo \
 RUN:   -macosx_version_min 0 \
 RUN:   -dependency_info /path/to/dependency_info.dat \
 RUN:   -mllvm -time-passes \
 RUN:   -objc_abi_version 2 \
 RUN:   -ios_simulator_version_min 9.0.0 \
 RUN:   -sdk_version 13.2
 RUN: not %lld -v --not-an-ignored-argument 2>&1 | FileCheck %s
-CHECK: error: unknown argument: --not-an-ignored-argument
+CHECK: error: unknown argument '--not-an-ignored-argument'