C++ CanType::getEnumOrBoundGenericEnum方法代码示例

static DynamicCastFeasibility
classifyDynamicCastFromProtocol(ModuleDecl *M, CanType source, CanType target,
                                bool isWholeModuleOpts) {
  assert(source.isExistentialType() &&
         "source should be an existential type");

  if (source == target)
    return DynamicCastFeasibility::WillSucceed;

  // Casts from class existential into a non-class can never succeed.
  if (source->isClassExistentialType() &&
      !target.isAnyExistentialType() &&
      !target.getClassOrBoundGenericClass() &&
      !isa<ArchetypeType>(target) &&
      !mayBridgeToObjectiveC(M, target)) {
    assert((target.getEnumOrBoundGenericEnum() ||
            target.getStructOrBoundGenericStruct() ||
            isa<TupleType>(target) ||
            isa<SILFunctionType>(target) ||
            isa<FunctionType>(target) ||
            isa<MetatypeType>(target)) &&
           "Target should be an enum, struct, tuple, metatype or function type");
    return DynamicCastFeasibility::WillFail;
  }

  // TODO: maybe prove that certain conformances are impossible?

  return DynamicCastFeasibility::MaySucceed;
}

//.........这里部分代码省略.........

    // Casts from class existential metatype into a concrete non-class metatype
    // can never succeed.
    if (source->isClassExistentialType() &&
        !target.isAnyExistentialType() &&
        !target.getClassOrBoundGenericClass())
      return DynamicCastFeasibility::WillFail;

    // TODO: prove that some conversions to existential metatype will
    // obviously succeed/fail.
    // TODO: prove that some conversions from class existential metatype
    // to a concrete non-class metatype will obviously fail.
    // TODO: class metatype to/from AnyObject
    // TODO: protocol concrete metatype to/from ObjCProtocol
    if (isa<ExistentialMetatypeType>(sourceMetatype) ||
        isa<ExistentialMetatypeType>(targetMetatype))
      return (getAnyMetatypeDepth(source) == getAnyMetatypeDepth(target)
              ? DynamicCastFeasibility::MaySucceed
              : DynamicCastFeasibility::WillFail);

    // If both metatypes are class metatypes, check if classes can be
    // cast.
    if (source.getClassOrBoundGenericClass() &&
        target.getClassOrBoundGenericClass())
      return classifyClassHierarchyCast(source, target);

    // Different structs cannot be cast to each other.
    if (source.getStructOrBoundGenericStruct() &&
        target.getStructOrBoundGenericStruct() &&
        source != target)
      return DynamicCastFeasibility::WillFail;

    // Different enums cannot be cast to each other.
    if (source.getEnumOrBoundGenericEnum() &&
        target.getEnumOrBoundGenericEnum() &&
        source != target)
      return DynamicCastFeasibility::WillFail;

    // If we don't know any better, assume that the cast may succeed.
    return DynamicCastFeasibility::MaySucceed;
  }

  // Function casts.
  if (auto sourceFunction = dyn_cast<FunctionType>(source)) {
    if (auto targetFunction = dyn_cast<FunctionType>(target)) {
      // A function cast can succeed if the function types can be identical,
      // or if the target type is throwier than the original.

      // A non-throwing source function can be cast to a throwing target type,
      // but not vice versa.
      if (sourceFunction->throws() && !targetFunction->throws())
        return DynamicCastFeasibility::WillFail;
      
      // The cast can't change the representation at runtime.
      if (targetFunction->getRepresentation()
            != sourceFunction->getRepresentation())
        return DynamicCastFeasibility::WillFail;
      
      if (sourceFunction.getInput() == targetFunction.getInput()
          && sourceFunction.getResult() == targetFunction.getResult())
        return DynamicCastFeasibility::WillSucceed;

      auto isSubstitutable = [](CanType a, CanType b) -> bool {
        // FIXME: Unnecessarily conservative; should structurally check for
        // substitutability.
        return a == b || a->hasArchetype() || b->hasArchetype();

/// Try to classify the dynamic-cast relationship between two types.
DynamicCastFeasibility
swift::classifyDynamicCast(Module *M,
                           CanType source,
                           CanType target,
                           bool isSourceTypeExact,
                           bool isWholeModuleOpts) {
  if (source == target) return DynamicCastFeasibility::WillSucceed;

  auto sourceObject = source.getAnyOptionalObjectType();
  auto targetObject = target.getAnyOptionalObjectType();

  // A common level of optionality doesn't affect the feasibility.
  if (sourceObject && targetObject) {
    return classifyDynamicCast(M, sourceObject, targetObject);

  // Nor does casting to a more optional type.
  } else if (targetObject) {
    return classifyDynamicCast(M, source, targetObject,
                               /* isSourceTypeExact */ false,
                               isWholeModuleOpts);

  // Casting to a less-optional type can always fail.
  } else if (sourceObject) {
    return weakenSuccess(classifyDynamicCast(M, sourceObject, target,
                                             /* isSourceTypeExact */ false,
                                             isWholeModuleOpts));
  }
  assert(!sourceObject && !targetObject);

  // Assume that casts to or from existential types or involving
  // dependent types can always succeed.  This is over-conservative.
  if (source->hasArchetype() || source.isExistentialType() ||
      target->hasArchetype() || target.isExistentialType()) {

    auto *SourceNominalTy = source.getAnyNominal();

    // Check conversions from non-protocol types into protocol types.
    if (!source.isExistentialType() &&
        SourceNominalTy &&
        target.isExistentialType())
      return classifyDynamicCastToProtocol(source, target, isWholeModuleOpts);

    // Casts from class existential into a non-class can never succeed.
    if (source->isClassExistentialType() &&
        !target.isAnyExistentialType() &&
        !target.getClassOrBoundGenericClass() &&
        !isa<ArchetypeType>(target) &&
        !mayBridgeToObjectiveC(M, target)) {
      assert((target.getEnumOrBoundGenericEnum() ||
              target.getStructOrBoundGenericStruct() ||
              isa<TupleType>(target) ||
              isa<SILFunctionType>(target) ||
              isa<FunctionType>(target) ||
              isa<MetatypeType>(target)) &&
             "Target should be an enum, struct, tuple, metatype or function type");
      return DynamicCastFeasibility::WillFail;
    }

    return DynamicCastFeasibility::MaySucceed;
  }

  // Metatype casts.
  if (auto sourceMetatype = dyn_cast<AnyMetatypeType>(source)) {
    auto targetMetatype = dyn_cast<AnyMetatypeType>(target);
    if (!targetMetatype) return DynamicCastFeasibility::WillFail;

    source = sourceMetatype.getInstanceType();
    target = targetMetatype.getInstanceType();

    if (source == target &&
        targetMetatype.isAnyExistentialType() ==
            sourceMetatype.isAnyExistentialType())
      return DynamicCastFeasibility::WillSucceed;

    if (targetMetatype.isAnyExistentialType() &&
        (isa<ProtocolType>(target) || isa<ProtocolCompositionType>(target))) {
      auto Feasibility = classifyDynamicCastToProtocol(source,
                                                       target,
                                                       isWholeModuleOpts);
      // Cast from existential metatype to existential metatype may still
      // succeed, even if we cannot prove anything statically.
      if (Feasibility != DynamicCastFeasibility::WillFail ||
          !sourceMetatype.isAnyExistentialType())
        return Feasibility;
    }

    // If isSourceTypeExact is true, we know we are casting the result of a
    // MetatypeInst instruction.
    if (isSourceTypeExact) {
      // If source or target are existentials, then it can be cast
      // successfully only into itself.
      if ((target.isAnyExistentialType() || source.isAnyExistentialType()) &&
          target != source)
        return DynamicCastFeasibility::WillFail;
    }

    // Casts from class existential metatype into a concrete non-class metatype
    // can never succeed.
    if (source->isClassExistentialType() &&
//.........这里部分代码省略.........