Enforce GPBFieldHasEnumDescriptor always being set.

Going back to the first ObjC support commit, there never really was support for
not have the EnumDescriptors, so start removing that partial support.

PiperOrigin-RevId: 488381501

objectivec/GPBDescriptor.m

@@ -443,16 +443,12 @@ uint32_t GPBFieldAlternateTag(GPBFieldDescriptor *self) {
   Class msgClass_;
 
   // Enum ivars.
-  // If protos are generated with GenerateEnumDescriptors on then it will
+  GPBEnumDescriptor *enumDescriptor_;
-  // be a enumDescriptor, otherwise it will be a enumVerifier.
-  union {
-    GPBEnumDescriptor *enumDescriptor_;
-    GPBEnumValidationFunc enumVerifier_;
-  } enumHandling_;
 }
 
 @synthesize msgClass = msgClass_;
 @synthesize containingOneof = containingOneof_;
+@synthesize enumDescriptor = enumDescriptor_;
 
 - (instancetype)initWithFieldDescription:(void *)description
                          includesDefault:(BOOL)includesDefault
@@ -518,11 +514,9 @@ uint32_t GPBFieldAlternateTag(GPBFieldDescriptor *self) {
         NSAssert(msgClass_, @"Class %s not defined", className);
       }
     } else if (dataType == GPBDataTypeEnum) {
-      if ((coreDesc->flags & GPBFieldHasEnumDescriptor) != 0) {
+      NSAssert((coreDesc->flags & GPBFieldHasEnumDescriptor) != 0,
-        enumHandling_.enumDescriptor_ = coreDesc->dataTypeSpecific.enumDescFunc();
+               @"Field must have GPBFieldHasEnumDescriptor set");
-      } else {
+      enumDescriptor_ = coreDesc->dataTypeSpecific.enumDescFunc();
-        enumHandling_.enumVerifier_ = coreDesc->dataTypeSpecific.enumVerifier;
-      }
     }
 
     // Non map<>/repeated fields can have defaults in proto2 syntax.
@@ -626,19 +620,7 @@ uint32_t GPBFieldAlternateTag(GPBFieldDescriptor *self) {
 
 - (BOOL)isValidEnumValue:(int32_t)value {
   NSAssert(description_->dataType == GPBDataTypeEnum, @"Field Must be of type GPBDataTypeEnum");
-  if (description_->flags & GPBFieldHasEnumDescriptor) {
+  return enumDescriptor_.enumVerifier(value);
-    return enumHandling_.enumDescriptor_.enumVerifier(value);
-  } else {
-    return enumHandling_.enumVerifier_(value);
-  }
-}
-
-- (GPBEnumDescriptor *)enumDescriptor {
-  if (description_->flags & GPBFieldHasEnumDescriptor) {
-    return enumHandling_.enumDescriptor_;
-  } else {
-    return nil;
-  }
 }
 
 - (GPBGenericValue)defaultValue {

objectivec/GPBDescriptor_PackagePrivate.h

@@ -52,7 +52,7 @@ typedef NS_OPTIONS(uint16_t, GPBFieldFlags) {
   // Indicates the field needs custom handling for the TextFormat name, if not
   // set, the name can be derived from the ObjC name.
   GPBFieldTextFormatNameCustom = 1 << 6,
-  // Indicates the field has an enum descriptor.
+  // This flag has never had any meaning, it was set on all enum fields.
   GPBFieldHasEnumDescriptor = 1 << 7,
 
   // These are not standard protobuf concepts, they are specific to the
@@ -89,10 +89,8 @@ typedef struct GPBMessageFieldDescription {
     // clazz is used iff GPBDescriptorInitializationFlag_UsesClassRefs is set.
     char *className;  // Name of the class of the message.
     Class clazz;      // Class of the message.
-    // For enums only: If EnumDescriptors are compiled in, it will be that,
+    // For enums only.
-    // otherwise it will be the verifier.
     GPBEnumDescriptorFunc enumDescFunc;
-    GPBEnumValidationFunc enumVerifier;
   } dataTypeSpecific;
   // The field number for the ivar.
   uint32_t number;