/// Can the given cast be performed by the scalar checked-cast
/// instructions?
///
/// CAUTION: if you introduce bridging conversions to the set of
/// things handleable by the scalar checked casts --- and that's not
/// totally unreasonable --- you will need to make the scalar checked
/// casts take a cast consumption kind.
bool swift::canUseScalarCheckedCastInstructions(SILModule &M,
CanType sourceType,
CanType targetType) {
// Look through one level of optionality on the source.
auto objectType = sourceType;
if (auto type = objectType.getAnyOptionalObjectType())
objectType = type;
// Casting to NSError needs to go through the indirect-cast case,
// since it may conform to ErrorType and require ErrorType-to-NSError
// bridging, unless we can statically see that the source type inherits
// NSError.
// A class-constrained archetype may be bound to NSError, unless it has a
// non-NSError superclass constraint. Casts to archetypes thus must always be
// indirect.
if (auto archetype = targetType->getAs<ArchetypeType>()) {
auto super = archetype->getSuperclass();
if (super.isNull())
return false;
// A base class constraint that isn't NSError rules out the archetype being
// bound to NSError.
if (auto nserror = M.Types.getNSErrorType())
return !super->isEqual(nserror);
// If NSError wasn't loaded, any base class constraint must not be NSError.
return true;
}
if (targetType == M.Types.getNSErrorType()) {
// If we statically know the target is an NSError subclass, then the cast
// can go through the scalar path (and it's trivially true so can be
// killed).
return targetType->isSuperclassOf(objectType, nullptr);
}
// Three supported cases:
// - metatype to metatype
// - metatype to object
// - object to object
if ((objectType.isAnyClassReferenceType() || isa<AnyMetatypeType>(objectType))
&& targetType->isAnyClassReferenceType())
return true;
if (isa<AnyMetatypeType>(objectType) && isa<AnyMetatypeType>(targetType))
return true;
// Otherwise, we need to use the general indirect-cast functions.
return false;
}
/// 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() &&
!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 classifyDynamicCast(M, source, target, false, isWholeModuleOpts);
// 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;
// A noreturn source function can be cast to a returning target type,
// but not vice versa.
// (noreturn isn't really reified at runtime though.)
if (targetFunction->isNoReturn() && !sourceFunction->isNoReturn())
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();
};
if (isSubstitutable(sourceFunction.getInput(), targetFunction.getInput())
&& isSubstitutable(targetFunction.getInput(),
targetFunction.getResult()))
return DynamicCastFeasibility::MaySucceed;
return DynamicCastFeasibility::WillFail;
}
}
// Class casts.
auto sourceClass = source.getClassOrBoundGenericClass();
auto targetClass = target.getClassOrBoundGenericClass();
if (sourceClass) {
if (targetClass) {
if (target->isSuperclassOf(source, nullptr))
return DynamicCastFeasibility::WillSucceed;
if (source->isSuperclassOf(target, nullptr))
return DynamicCastFeasibility::MaySucceed;
// FIXME: bridged types, e.g. CF <-> NS (but not for metatypes).
return DynamicCastFeasibility::WillFail;
}
// In the Objective-C runtime, class metatypes are also class instances.
// The cast may succeed if the target type can be inhabited by a class
// metatype.
// TODO: Narrow this to the sourceClass being exactly NSObject.
if (M->getASTContext().LangOpts.EnableObjCInterop) {
if (auto targetMeta = dyn_cast<MetatypeType>(target)) {
if (isa<ArchetypeType>(targetMeta.getInstanceType())
|| targetMeta.getInstanceType()->mayHaveSuperclass())
return DynamicCastFeasibility::MaySucceed;
} else if (isa<ExistentialMetatypeType>(target)) {
return DynamicCastFeasibility::MaySucceed;
}
}
}
// If the source is not existential, an archetype, or (under the ObjC runtime)
// a class, and the destination is a metatype, there is no way the cast can
// succeed.
if (target->is<AnyMetatypeType>()) return DynamicCastFeasibility::WillFail;
// FIXME: tuple conversions?
// FIXME: Be more careful with briding conversions from
// NSArray, NSDictionary and NSSet as they may fail?
// Check if there might be a bridging conversion.
if (source->isBridgeableObjectType() && mayBridgeToObjectiveC(M, target)) {
// Try to get the ObjC type which is bridged to target type.
assert(!target.isAnyExistentialType());
Optional<Type> ObjCTy = M->getASTContext().getBridgedToObjC(
M, target, nullptr);
if (ObjCTy && ObjCTy.getValue()) {
// If the bridged ObjC type is known, check if
// source type can be cast into it.
return classifyDynamicCast(M, source,
ObjCTy.getValue().getCanonicalTypeOrNull(),
/* isSourceTypeExact */ false, isWholeModuleOpts);
}
return DynamicCastFeasibility::MaySucceed;
}
if (target->isBridgeableObjectType() && mayBridgeToObjectiveC(M, source)) {
// Try to get the ObjC type which is bridged to source type.
assert(!source.isAnyExistentialType());
Optional<Type> ObjCTy = M->getASTContext().getBridgedToObjC(
M, source, nullptr);
if (ObjCTy && ObjCTy.getValue()) {
// If the bridged ObjC type is known, check if
// this type can be cast into target type.
return classifyDynamicCast(M,
ObjCTy.getValue().getCanonicalTypeOrNull(),
target,
/* isSourceTypeExact */ false, isWholeModuleOpts);
}
return DynamicCastFeasibility::MaySucceed;
}
// Check if it is a cast between bridged error types.
if (isErrorType(M, source) && isErrorType(M, target)) {
// TODO: Cast to NSError succeeds always.
return DynamicCastFeasibility::MaySucceed;
}
return DynamicCastFeasibility::WillFail;
}