/**
* Check if cast from supertype to subtype is erased. It is an error in "is" statement and warning
* in "as".
*/
public static boolean isCastErased(
@NotNull KotlinType supertype,
@NotNull KotlinType subtype,
@NotNull KotlinTypeChecker typeChecker) {
// cast between T and T? is always OK
if (supertype.isMarkedNullable() || subtype.isMarkedNullable()) {
return isCastErased(
TypeUtils.makeNotNullable(supertype), TypeUtils.makeNotNullable(subtype), typeChecker);
}
// if it is a upcast, it's never erased
if (typeChecker.isSubtypeOf(supertype, subtype)) return false;
// downcasting to a non-reified type parameter is always erased
if (TypeUtils.isNonReifiedTypeParemeter(subtype)) return true;
// Check that we are actually casting to a generic type
// NOTE: this does not account for 'as Array<List<T>>'
if (allParametersReified(subtype)) return false;
KotlinType staticallyKnownSubtype =
findStaticallyKnownSubtype(supertype, subtype.getConstructor()).getResultingType();
// If the substitution failed, it means that the result is an impossible type, e.g. something
// like Out<in Foo>
// In this case, we can't guarantee anything, so the cast is considered to be erased
if (staticallyKnownSubtype == null) return true;
// If the type we calculated is a subtype of the cast target, it's OK to use the cast target
// instead.
// If not, it's wrong to use it
return !typeChecker.isSubtypeOf(staticallyKnownSubtype, subtype);
}
/**
* Remember that we are trying to cast something of type {@code supertype} to {@code subtype}.
*
* <p>Since at runtime we can only check the class (type constructor), the rest of the subtype
* should be known statically, from supertype. This method reconstructs all static information
* that can be obtained from supertype.
*
* <p>Example 1: supertype = Collection<String> subtype = List<...> result = List<String>, all
* arguments are inferred
*
* <p>Example 2: supertype = Any subtype = List<...> result = List<*>, some arguments were not
* inferred, replaced with '*'
*/
public static TypeReconstructionResult findStaticallyKnownSubtype(
@NotNull KotlinType supertype, @NotNull TypeConstructor subtypeConstructor) {
assert !supertype.isMarkedNullable() : "This method only makes sense for non-nullable types";
// Assume we are casting an expression of type Collection<Foo> to List<Bar>
// First, let's make List<T>, where T is a type variable
ClassifierDescriptor descriptor = subtypeConstructor.getDeclarationDescriptor();
assert descriptor != null : "Can't create default type for " + subtypeConstructor;
KotlinType subtypeWithVariables = descriptor.getDefaultType();
// Now, let's find a supertype of List<T> that is a Collection of something,
// in this case it will be Collection<T>
KotlinType supertypeWithVariables =
TypeCheckingProcedure.findCorrespondingSupertype(subtypeWithVariables, supertype);
final List<TypeParameterDescriptor> variables =
subtypeWithVariables.getConstructor().getParameters();
Map<TypeConstructor, TypeProjection> substitution;
if (supertypeWithVariables != null) {
// Now, let's try to unify Collection<T> and Collection<Foo> solution is a map from T to Foo
TypeUnifier.UnificationResult solution =
TypeUnifier.unify(
new TypeProjectionImpl(supertype),
new TypeProjectionImpl(supertypeWithVariables),
new Predicate<TypeConstructor>() {
@Override
public boolean apply(TypeConstructor typeConstructor) {
ClassifierDescriptor descriptor = typeConstructor.getDeclarationDescriptor();
return descriptor instanceof TypeParameterDescriptor
&& variables.contains(descriptor);
}
});
substitution = Maps.newHashMap(solution.getSubstitution());
} else {
// If there's no corresponding supertype, no variables are determined
// This may be OK, e.g. in case 'Any as List<*>'
substitution = Maps.newHashMapWithExpectedSize(variables.size());
}
// If some of the parameters are not determined by unification, it means that these parameters
// are lost,
// let's put stars instead, so that we can only cast to something like List<*>, e.g. (a: Any) as
// List<*>
boolean allArgumentsInferred = true;
for (TypeParameterDescriptor variable : variables) {
TypeProjection value = substitution.get(variable.getTypeConstructor());
if (value == null) {
substitution.put(variable.getTypeConstructor(), TypeUtils.makeStarProjection(variable));
allArgumentsInferred = false;
}
}
// At this point we have values for all type parameters of List
// Let's make a type by substituting them: List<T> -> List<Foo>
KotlinType substituted =
TypeSubstitutor.create(substitution).substitute(subtypeWithVariables, Variance.INVARIANT);
return new TypeReconstructionResult(substituted, allArgumentsInferred);
}
/**
* Differs from `isNullableType` only by treating type parameters: acceptsNullable(T) <=> T has
* nullable lower bound Semantics should be the same as `isSubtype(Nothing?, T)`
*
* @return true if `null` can be assigned to storage of this type
*/
public static boolean acceptsNullable(@NotNull KotlinType type) {
if (type.isMarkedNullable()) {
return true;
}
if (FlexibleTypesKt.isFlexible(type)
&& acceptsNullable(FlexibleTypesKt.flexibility(type).getUpperBound())) {
return true;
}
return false;
}
@Nullable
public static KotlinType createSubstitutedSupertype(
@NotNull KotlinType subType,
@NotNull KotlinType superType,
@NotNull TypeSubstitutor substitutor) {
KotlinType substitutedType = substitutor.substitute(superType, Variance.INVARIANT);
if (substitutedType != null) {
return makeNullableIfNeeded(substitutedType, subType.isMarkedNullable());
}
return null;
}
public static boolean hasNullableSuperType(@NotNull KotlinType type) {
if (type.getConstructor().getDeclarationDescriptor() instanceof ClassDescriptor) {
// A class/trait cannot have a nullable supertype
return false;
}
for (KotlinType supertype : getImmediateSupertypes(type)) {
if (supertype.isMarkedNullable()) return true;
if (hasNullableSuperType(supertype)) return true;
}
return false;
}
/**
* A work-around of the generic nullability problem in the type checker Semantics should be the
* same as `!isSubtype(T, Any)`
*
* @return true if a value of this type can be null
*/
public static boolean isNullableType(@NotNull KotlinType type) {
if (type.isMarkedNullable()) {
return true;
}
if (FlexibleTypesKt.isFlexible(type)
&& isNullableType(FlexibleTypesKt.flexibility(type).getUpperBound())) {
return true;
}
if (isTypeParameter(type)) {
return hasNullableSuperType(type);
}
return false;
}
@NotNull
public static KotlinType makeNullableAsSpecified(@NotNull KotlinType type, boolean nullable) {
Flexibility flexibility = type.getCapability(Flexibility.class);
if (flexibility != null) {
return flexibility.makeNullableAsSpecified(nullable);
}
// Wrapping serves two purposes here
// 1. It's requires less memory than copying with a changed nullability flag: a copy has many
// fields, while a wrapper has only one
// 2. It preserves laziness of types
// Unwrap to avoid long delegation call chains
if (type instanceof AbstractTypeWithKnownNullability) {
return makeNullableAsSpecified(((AbstractTypeWithKnownNullability) type).delegate, nullable);
}
// checking to preserve laziness
if (!(type instanceof LazyType) && type.isMarkedNullable() == nullable) {
return type;
}
return nullable ? new NullableType(type) : new NotNullType(type);
}
private static boolean isNotNullConstructedFromGivenClass(
@NotNull KotlinType type, @NotNull FqNameUnsafe fqName) {
return !type.isMarkedNullable() && isConstructedFromGivenClass(type, fqName);
}
public static boolean isPrimitiveType(@NotNull KotlinType type) {
ClassifierDescriptor descriptor = type.getConstructor().getDeclarationDescriptor();
return !type.isMarkedNullable()
&& descriptor instanceof ClassDescriptor
&& isPrimitiveClass((ClassDescriptor) descriptor);
}
public static boolean isNullableAny(@NotNull KotlinType type) {
return isAnyOrNullableAny(type) && type.isMarkedNullable();
}
public static boolean isNullableNothing(@NotNull KotlinType type) {
return isNothingOrNullableNothing(type) && type.isMarkedNullable();
}
public static boolean canHaveSubtypes(KotlinTypeChecker typeChecker, @NotNull KotlinType type) {
if (type.isMarkedNullable()) {
return true;
}
if (!type.getConstructor().isFinal()) {
return true;
}
List<TypeParameterDescriptor> parameters = type.getConstructor().getParameters();
List<TypeProjection> arguments = type.getArguments();
for (int i = 0, parametersSize = parameters.size(); i < parametersSize; i++) {
TypeParameterDescriptor parameterDescriptor = parameters.get(i);
TypeProjection typeProjection = arguments.get(i);
if (typeProjection.isStarProjection()) return true;
Variance projectionKind = typeProjection.getProjectionKind();
KotlinType argument = typeProjection.getType();
switch (parameterDescriptor.getVariance()) {
case INVARIANT:
switch (projectionKind) {
case INVARIANT:
if (lowerThanBound(typeChecker, argument, parameterDescriptor)
|| canHaveSubtypes(typeChecker, argument)) {
return true;
}
break;
case IN_VARIANCE:
if (lowerThanBound(typeChecker, argument, parameterDescriptor)) {
return true;
}
break;
case OUT_VARIANCE:
if (canHaveSubtypes(typeChecker, argument)) {
return true;
}
break;
}
break;
case IN_VARIANCE:
if (projectionKind != Variance.OUT_VARIANCE) {
if (lowerThanBound(typeChecker, argument, parameterDescriptor)) {
return true;
}
} else {
if (canHaveSubtypes(typeChecker, argument)) {
return true;
}
}
break;
case OUT_VARIANCE:
if (projectionKind != Variance.IN_VARIANCE) {
if (canHaveSubtypes(typeChecker, argument)) {
return true;
}
} else {
if (lowerThanBound(typeChecker, argument, parameterDescriptor)) {
return true;
}
}
break;
}
}
return false;
}