[Frontend/Serialization] Remove ExtensibleEnums experimental flag

For now the semantics provided by `@extensible` keyword on per-enum
basis. We might return this as an upcoming feature in the future with
a way to opt-out.

(cherry picked from commit bf19481)

Author: xedin

include/swift/AST/Decl.h

@@ -751,7 +751,7 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl>, public Swi
     HasAnyUnavailableDuringLoweringValues : 1
   );
 
-  SWIFT_INLINE_BITFIELD(ModuleDecl, TypeDecl, 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+8,
+  SWIFT_INLINE_BITFIELD(ModuleDecl, TypeDecl, 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+8,
     /// If the module is compiled as static library.
     StaticLibrary : 1,
 
@@ -820,10 +820,7 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl>, public Swi
     SerializePackageEnabled : 1,
 
     /// Whether this module has enabled strict memory safety checking.
-    StrictMemorySafety : 1,
-
-    /// Whether this module has enabled `ExtensibleEnums` feature.
-    ExtensibleEnums : 1
+    StrictMemorySafety : 1
   );
 
   SWIFT_INLINE_BITFIELD(PrecedenceGroupDecl, Decl, 1+2,

include/swift/AST/Module.h

@@ -835,14 +835,6 @@ class ModuleDecl
     Bits.ModuleDecl.ObjCNameLookupCachePopulated = value;
   }
 
-  bool supportsExtensibleEnums() const {
-    return Bits.ModuleDecl.ExtensibleEnums;
-  }
-
-  void setSupportsExtensibleEnums(bool value = true) {
-    Bits.ModuleDecl.ExtensibleEnums = value;
-  }
-
   /// For the main module, retrieves the list of primary source files being
   /// compiled, that is, the files we're generating code for.
   ArrayRef<SourceFile *> getPrimarySourceFiles() const;

include/swift/Basic/Features.def

@@ -505,11 +505,6 @@ SUPPRESSIBLE_EXPERIMENTAL_FEATURE(AddressableTypes, true)
 /// Allow custom availability domains to be defined and referenced.
 EXPERIMENTAL_FEATURE(CustomAvailability, true)
 
-/// Allow public enumerations to be extensible by default
-/// regardless of whether the module they are declared in
-/// is resilient or not.
-EXPERIMENTAL_FEATURE(ExtensibleEnums, true)
-
 /// Syntax sugar features for concurrency.
 EXPERIMENTAL_FEATURE(ConcurrencySyntaxSugar, true)
 

include/swift/Serialization/Validation.h

@@ -150,7 +150,6 @@ class ExtendedValidationInfo {
     unsigned AllowNonResilientAccess: 1;
     unsigned SerializePackageEnabled: 1;
     unsigned StrictMemorySafety: 1;
-    unsigned SupportsExtensibleEnums : 1;
   } Bits;
 
 public:
@@ -272,11 +271,6 @@ class ExtendedValidationInfo {
             version, SourceLoc(), /*Diags=*/nullptr))
       SwiftInterfaceCompilerVersion = genericVersion.value();
   }
-
-  bool supportsExtensibleEnums() const { return Bits.SupportsExtensibleEnums; }
-  void setSupportsExtensibleEnums(bool val) {
-    Bits.SupportsExtensibleEnums = val;
-  }
 };
 
 struct SearchPath {

lib/AST/FeatureSet.cpp

@@ -124,7 +124,6 @@ UNINTERESTING_FEATURE(Volatile)
 UNINTERESTING_FEATURE(SuppressedAssociatedTypes)
 UNINTERESTING_FEATURE(StructLetDestructuring)
 UNINTERESTING_FEATURE(MacrosOnImports)
-UNINTERESTING_FEATURE(ExtensibleEnums)
 UNINTERESTING_FEATURE(NonisolatedNonsendingByDefault)
 UNINTERESTING_FEATURE(KeyPathWithMethodMembers)
 UNINTERESTING_FEATURE(NoExplicitNonIsolated)

lib/Frontend/Frontend.cpp

@@ -1501,8 +1501,6 @@ ModuleDecl *CompilerInstance::getMainModule() const {
       MainModule->setSerializePackageEnabled();
     if (Invocation.getLangOptions().hasFeature(Feature::StrictMemorySafety))
       MainModule->setStrictMemorySafety(true);
-    if (Invocation.getLangOptions().hasFeature(Feature::ExtensibleEnums))
-      MainModule->setSupportsExtensibleEnums(true);
 
     configureAvailabilityDomains(getASTContext(),
                                  Invocation.getFrontendOptions(), MainModule);

lib/Serialization/ModuleFile.h

@@ -714,11 +714,6 @@ class ModuleFile
   /// \c true if this module was built with strict memory safety.
   bool strictMemorySafety() const { return Core->strictMemorySafety(); }
 
-  /// \c true if this module was built with `ExtensibleEnums` feature enabled.
-  bool supportsExtensibleEnums() const {
-    return Core->supportsExtensibleEnums();
-  }
-
   /// Associates this module file with the AST node representing it.
   ///
   /// Checks that the file is compatible with the AST module it's being loaded

lib/Serialization/ModuleFileSharedCore.cpp

@@ -225,9 +225,6 @@ static bool readOptionsBlock(llvm::BitstreamCursor &cursor,
     case options_block::STRICT_MEMORY_SAFETY:
       extendedInfo.setStrictMemorySafety(true);
       break;
-    case options_block::EXTENSIBLE_ENUMS:
-      extendedInfo.setSupportsExtensibleEnums(true);
-      break;
     default:
       // Unknown options record, possibly for use by a future version of the
       // module format.
@@ -1507,7 +1504,6 @@ ModuleFileSharedCore::ModuleFileSharedCore(
       Bits.AllowNonResilientAccess = extInfo.allowNonResilientAccess();
       Bits.SerializePackageEnabled = extInfo.serializePackageEnabled();
       Bits.StrictMemorySafety = extInfo.strictMemorySafety();
-      Bits.SupportsExtensibleEnums = extInfo.supportsExtensibleEnums();
       MiscVersion = info.miscVersion;
       SDKVersion = info.sdkVersion;
       ModuleABIName = extInfo.getModuleABIName();

lib/Serialization/ModuleFileSharedCore.h

@@ -421,11 +421,8 @@ class ModuleFileSharedCore {
     /// Whether this module enabled strict memory safety.
     unsigned StrictMemorySafety : 1;
 
-    /// Whether this module enabled has `ExtensibleEnums` feature enabled.
-    unsigned SupportsExtensibleEnums : 1;
-
     // Explicitly pad out to the next word boundary.
-    unsigned : 1;
+    unsigned : 2;
   } Bits = {};
   static_assert(sizeof(ModuleBits) <= 8, "The bit set should be small");
 
@@ -688,8 +685,6 @@ class ModuleFileSharedCore {
 
   bool strictMemorySafety() const { return Bits.StrictMemorySafety; }
 
-  bool supportsExtensibleEnums() const { return Bits.SupportsExtensibleEnums; }
-
   /// How should \p dependency be loaded for a transitive import via \c this?
   ///
   /// If \p importNonPublicDependencies, more transitive dependencies

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 945;  // @extensible attribute
+const uint16_t SWIFTMODULE_VERSION_MINOR = 946; // remove ExtensibleEnums feature
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -987,8 +987,7 @@ namespace options_block {
     CXX_STDLIB_KIND,
     PUBLIC_MODULE_NAME,
     SWIFT_INTERFACE_COMPILER_VERSION,
-    STRICT_MEMORY_SAFETY,
-    EXTENSIBLE_ENUMS,
+    STRICT_MEMORY_SAFETY
   };
 
   using SDKPathLayout = BCRecordLayout<
@@ -1098,10 +1097,6 @@ namespace options_block {
     SWIFT_INTERFACE_COMPILER_VERSION,
     BCBlob // version tuple
   >;
-
-  using ExtensibleEnumsLayout = BCRecordLayout<
-    EXTENSIBLE_ENUMS
-  >;
 }
 
 /// The record types within the input block.