Revert "[interop][SwiftToCxx] add -enable-experimental-cxx-interop-in-clang-header flag that lets you enable reverse interop only"

This reverts commit c193a63.

Author: hyp

include/swift/Frontend/FrontendOptions.h

@@ -413,10 +413,6 @@ class FrontendOptions {
   /// header.
   llvm::Optional<ClangHeaderExposeBehavior> ClangHeaderExposedDecls;
 
-  /// Emit C++ bindings for the exposed Swift declarations in the generated
-  /// clang header.
-  bool EnableExperimentalCxxInteropInClangHeader = false;
-
   /// \return true if the given action only parses without doing other compilation steps.
   static bool shouldActionOnlyParse(ActionType);
 

include/swift/Option/Options.td

@@ -662,11 +662,6 @@ def experimental_c_foreign_reference_types :
   Flags<[FrontendOption, HelpHidden, ModuleInterfaceOption]>,
   HelpText<"Enable experimental C foreign references types (with reference coutning).">;
 
-def enable_experimental_cxx_interop_in_clang_header :
-  Flag<["-"], "enable-experimental-cxx-interop-in-clang-header">,
-  Flags<[FrontendOption, NoDriverOption, HelpHidden]>,
-  HelpText<"Enable experimental Swift to C++ interop code generation in generated Clang header">;
-
 def experimental_cxx_stdlib :
   Separate<["-"], "experimental-cxx-stdlib">,
   Flags<[HelpHidden]>,

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -316,8 +316,6 @@ bool ArgsToFrontendOptionsConverter::convert(
               .Case("has-expose-attr", FrontendOptions::ClangHeaderExposeBehavior::HasExposeAttr)
               .Default(llvm::None);
   }
-  Opts.EnableExperimentalCxxInteropInClangHeader =
-      Args.hasArg(OPT_enable_experimental_cxx_interop_in_clang_header);
 
   Opts.StrictImplicitModuleContext = Args.hasArg(OPT_strict_implicit_module_context,
                                                  OPT_no_strict_implicit_module_context,

lib/PrintAsClang/PrintAsClang.cpp

@@ -556,7 +556,6 @@ bool swift::printAsClangHeader(raw_ostream &os, ModuleDecl *M,
   emitCxxConditional(os, [&] {
     // FIXME: Expose Swift with @expose by default.
     bool enableCxx = frontendOpts.ClangHeaderExposedDecls.has_value() ||
-                     frontendOpts.EnableExperimentalCxxInteropInClangHeader ||
                      M->DeclContext::getASTContext().LangOpts.EnableCXXInterop;
     if (!enableCxx)
       return;

test/Interop/SwiftToCxx/expose-attr/expose-swift-decls-to-cxx.swift

@@ -4,9 +4,6 @@
 
 // RUN: %check-interop-cxx-header-in-clang(%t/expose.h -Wno-error=unused-function)
 
-// RUN: %target-swift-frontend %s -typecheck -module-name Expose -enable-experimental-cxx-interop-in-clang-header -clang-header-expose-decls=has-expose-attr -emit-clang-header-path %t/expose.h
-// RUN: %FileCheck %s < %t/expose.h
-
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-frontend %s -emit-module -module-name Expose -o %t
 // RUN: %target-swift-frontend -parse-as-library %t/Expose.swiftmodule -typecheck -module-name Expose -enable-experimental-cxx-interop -clang-header-expose-decls=has-expose-attr -emit-clang-header-path %t/expose.h