[Driver] Completely remove -emit-public-type-metadata-accessors.

This was retained to help ease migration between versions of the 4.2 compiler
between when the flag was originally introduced and the full fix landed. It's
not longer needed and there's no reason to retain it in the full release.

Fixes rdar://problem/40502379.

Author: huonw

include/swift/AST/DiagnosticsDriver.def

@@ -155,10 +155,6 @@ WARNING(warn_use_filelists_deprecated, none,
         "the option '-driver-use-filelists' is deprecated; use "
         "'-driver-filelist-threshold=0' instead", ())
 
-WARNING(warn_emit_public_type_metadata_accessors_deprecated, none,
-        "the option '-emit-public-type-metadata-accessors' is no longer "
-        "needed and is deprecated; consider removing it", ())
-
 ERROR(cannot_find_migration_script, none,
       "missing migration script from path '%0'", (StringRef))
 

include/swift/Option/Options.td

@@ -355,11 +355,6 @@ def warn_swift3_objc_inference : Flag<["-"], "warn-swift3-objc-inference">,
   Alias<warn_swift3_objc_inference_complete>,
   Flags<[FrontendOption, DoesNotAffectIncrementalBuild, HelpHidden]>;
 
-def emit_public_type_metadata_accessors :
-  Flag<["-"], "emit-public-type-metadata-accessors">,
-  Flags<[FrontendOption]>,
-  HelpText<"Emit all type metadata accessors as public (deprecated: now does nothing)">;
-
 def Rpass_EQ : Joined<["-"], "Rpass=">,
   Flags<[FrontendOption]>,
   HelpText<"Report performed transformations by optimization passes whose "

lib/Driver/Driver.cpp

@@ -244,10 +244,6 @@ static void validateArgs(DiagnosticEngine &diags, const ArgList &args) {
   validateDebugInfoArgs(diags, args);
   validateCompilationConditionArgs(diags, args);
   validateAutolinkingArgs(diags, args);
-
-  if (args.hasArg(options::OPT_emit_public_type_metadata_accessors))
-    diags.diagnose(SourceLoc(),
-                   diag::warn_emit_public_type_metadata_accessors_deprecated);
 }
 
 std::unique_ptr<ToolChain>