[ParseableInterface] Turn on -enable-parseable-module-interface always (swiftlang#23331)

...and remove the option. This is ~technically~ CLI-breaking because
Swift 5 shipped this as a hidden driver option, but it wouldn't have
/done/ anything in Swift 5, so I think it's okay to remove.

Note that if a parseable interface (.swiftinterface) and a binary
interface (.swiftmodule) are both present, the binary one will still
be preferred. This just /allows/ parseable interfaces to be used.

rdar://problem/36885834

Author: jrose-apple

include/swift/Frontend/FrontendOptions.h

@@ -220,9 +220,6 @@ class FrontendOptions {
   /// (if asked to emit SIL).
   bool EmitVerboseSIL = false;
 
-  /// If set, find and import parseable modules from .swiftinterface files.
-  bool EnableParseableModuleInterface = false;
-
   /// If set, this module is part of a mixed Objective-C/Swift framework, and
   /// the Objective-C half should implicitly be visible to the Swift sources.
   bool ImportUnderlyingModule = false;

include/swift/Option/Options.td

@@ -346,11 +346,6 @@ def emit_parseable_module_interface_path :
   Flags<[FrontendOption, NoInteractiveOption, DoesNotAffectIncrementalBuild,
          ArgumentIsPath]>,
   MetaVarName<"<path>">, HelpText<"Output parseable interface file to <path>">;
-def enable_parseable_module_interface :
-  Flag<["-"], "enable-parseable-module-interface">,
-  Flags<[FrontendOption, HelpHidden, NoInteractiveOption,
-         DoesNotAffectIncrementalBuild]>,
-  HelpText<"Accept parseable .swiftinterface form of modules">;
 
 def emit_objc_header : Flag<["-"], "emit-objc-header">,
   Flags<[FrontendOption, NoInteractiveOption, DoesNotAffectIncrementalBuild]>,

lib/Driver/ToolChains.cpp

@@ -193,7 +193,6 @@ static void addCommonFrontendArgs(const ToolChain &TC, const OutputInfo &OI,
   inputArgs.AddLastArg(arguments, options::OPT_import_underlying_module);
   inputArgs.AddLastArg(arguments, options::OPT_module_cache_path);
   inputArgs.AddLastArg(arguments, options::OPT_module_link_name);
-  inputArgs.AddLastArg(arguments, options::OPT_enable_parseable_module_interface);
   inputArgs.AddLastArg(arguments, options::OPT_nostdimport);
   inputArgs.AddLastArg(arguments, options::OPT_parse_stdlib);
   inputArgs.AddLastArg(arguments, options::OPT_resource_dir);

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -167,8 +167,6 @@ bool ArgsToFrontendOptionsConverter::convert(
 
   Opts.EnableSourceImport |= Args.hasArg(OPT_enable_source_import);
   Opts.ImportUnderlyingModule |= Args.hasArg(OPT_import_underlying_module);
-  Opts.EnableParseableModuleInterface |=
-      Args.hasArg(OPT_enable_parseable_module_interface);
   Opts.EnableSerializationNestedTypeLookupTable &=
       !Args.hasArg(OPT_disable_serialization_nested_type_lookup_table);
 

lib/Frontend/Frontend.cpp

@@ -293,10 +293,7 @@ bool CompilerInstance::setUpModuleLoaders() {
                                                   enableLibraryEvolution,
                                                   getDependencyTracker()));
   }
-  auto MLM = ModuleLoadingMode::OnlySerialized;
-  if (Invocation.getFrontendOptions().EnableParseableModuleInterface) {
-    MLM = ModuleLoadingMode::PreferSerialized;
-  }
+  auto MLM = ModuleLoadingMode::PreferSerialized;
   if (auto forceModuleLoadingMode =
       llvm::sys::Process::GetEnv("SWIFT_FORCE_MODULE_LOADING")) {
     if (*forceModuleLoadingMode == "prefer-parseable")

lib/Frontend/ParseableInterfaceModuleLoader.cpp

@@ -258,7 +258,6 @@ class swift::ParseableInterfaceBuilder {
   void configureSubInvocationInputsAndOutputs(StringRef OutPath) {
     auto &SubFEOpts = subInvocation.getFrontendOptions();
     SubFEOpts.RequestedAction = FrontendOptions::ActionType::EmitModuleOnly;
-    SubFEOpts.EnableParseableModuleInterface = true;
     SubFEOpts.InputsAndOutputs.addPrimaryInputFile(interfacePath);
     SupplementaryOutputPaths SOPs;
     SOPs.ModuleOutputPath = OutPath.str();
@@ -713,9 +712,6 @@ class ParseableInterfaceModuleLoaderImpl {
     if (validationInfo.status != serialization::Status::Valid)
       return false;
 
-    assert(validationInfo.name == moduleName &&
-           "we built a module at this path with a different name?");
-
     return dependenciesAreUpToDate(allDeps);
   }
 

test/ParseableInterface/ModuleCache/ObjCAttrWithoutFoundation.swiftinterface

@@ -2,7 +2,7 @@
 // swift-module-flags: -module-name ObjCAttrWithoutFoundation -enable-library-evolution -enable-objc-interop
 
 // RUN: %empty-directory(%t)
-// RUN: echo 'import ObjCAttrWithoutFoundation' | %target-swift-frontend -typecheck -enable-parseable-module-interface -module-cache-path %t -I %S -
+// RUN: echo 'import ObjCAttrWithoutFoundation' | %target-swift-frontend -typecheck -module-cache-path %t -I %S -
 
 public class MyClass {
   public init()

test/ParseableInterface/ModuleCache/SerializedSIL.swiftinterface

@@ -2,7 +2,7 @@
 // swift-module-flags: -module-name SerializedSIL -enable-library-evolution
 
 // RUN: %empty-directory(%t)
-// RUN: echo 'import SerializedSIL' | %target-swift-frontend -typecheck -enable-parseable-module-interface -module-cache-path %t -I %S -
+// RUN: echo 'import SerializedSIL' | %target-swift-frontend -typecheck -module-cache-path %t -I %S -
 // RUN: %target-sil-opt -disable-sil-linking %t/SerializedSIL-*.swiftmodule -module-name SerializedSIL > %t/SerializedSIL.sil
 // RUN: %FileCheck %s < %t/SerializedSIL.sil
 // RUN: %FileCheck -check-prefix NEGATIVE %s < %t/SerializedSIL.sil

test/ParseableInterface/ModuleCache/WrongName.swiftinterface

@@ -2,6 +2,6 @@
 // swift-module-flags: -module-name DreadPirateRoberts
 
 // RUN: %empty-directory(%t)
-// RUN: echo 'import WrongName' | not %target-swift-frontend -typecheck -enable-parseable-module-interface -module-cache-path %t -I %S - 2>&1 | %FileCheck %s
+// RUN: echo 'import WrongName' | not %target-swift-frontend -typecheck -module-cache-path %t -I %S - 2>&1 | %FileCheck %s
 
 // CHECK: :1:8: error: cannot load module 'DreadPirateRoberts' as 'WrongName'

test/ParseableInterface/ModuleCache/force-module-loading-mode-archs.swift

@@ -16,7 +16,7 @@
 // RUN: not env SWIFT_FORCE_MODULE_LOADING=only-parseable %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP %s -I %t 2>&1 | %FileCheck -check-prefix=FROM-INTERFACE %s
 // RUN: not env SWIFT_FORCE_MODULE_LOADING=only-serialized %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP %s -I %t 2>&1 | %FileCheck -check-prefix=NO-SUCH-MODULE %s
 // (default)
-// RUN: not %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP -I %t %s 2>&1 | %FileCheck -check-prefix=NO-SUCH-MODULE %s
+// RUN: not %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP -I %t %s 2>&1 | %FileCheck -check-prefix=FROM-INTERFACE %s
 
 // 3. Only module is present.
 // RUN: %empty-directory(%t/Lib.swiftmodule)
@@ -53,7 +53,7 @@
 // RUN: not env SWIFT_FORCE_MODULE_LOADING=only-parseable %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP %s -I %t 2>&1 | %FileCheck -check-prefix=FROM-INTERFACE %s
 // RUN: not env SWIFT_FORCE_MODULE_LOADING=only-serialized %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP %s -I %t 2>&1 | %FileCheck -check-prefix=BAD-MODULE %s
 // (default)
-// RUN: not %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP -I %t %s 2>&1 | %FileCheck -check-prefix=BAD-MODULE %s
+// RUN: not %target-swift-frontend -typecheck -parse-stdlib -module-cache-path %t/MCP -I %t %s 2>&1 | %FileCheck -check-prefix=FROM-INTERFACE %s
 
 // 6. Both are present but the module can't be opened.
 // RUN: chmod a-r %t/Lib.swiftmodule/%target-swiftmodule-name