@Override
public boolean isSubtype(JSType that) {
if (JSType.isSubtypeHelper(this, that)) {
return true;
}
// Union types
if (that.isUnionType()) {
// The static {@code JSType.isSubtype} check already decomposed
// union types, so we don't need to check those again.
return false;
}
// record types
if (that.isRecordType()) {
return RecordType.isSubtype(this, that.toMaybeRecordType());
}
// Interfaces
// Find all the interfaces implemented by this class and compare each one
// to the interface instance.
ObjectType thatObj = that.toObjectType();
ObjectType thatCtor = thatObj == null ? null : thatObj.getConstructor();
if (thatCtor != null && thatCtor.isInterface()) {
Iterable<ObjectType> thisInterfaces = getCtorImplementedInterfaces();
for (ObjectType thisInterface : thisInterfaces) {
if (thisInterface.isSubtype(that)) {
return true;
}
}
}
if (getConstructor() != null && getConstructor().isInterface()) {
for (ObjectType thisInterface : getCtorExtendedInterfaces()) {
if (thisInterface.isSubtype(that)) {
return true;
}
}
}
// other prototype based objects
if (isUnknownType() || implicitPrototypeChainIsUnknown()) {
// If unsure, say 'yes', to avoid spurious warnings.
// TODO(user): resolve the prototype chain completely in all cases,
// to avoid guessing.
return true;
}
return this.isImplicitPrototype(thatObj);
}
/**
* A function is a subtype of another if their call methods are related via subtyping and {@code
* this} is a subtype of {@code that} with regard to the prototype chain.
*/
@Override
public boolean isSubtype(JSType that) {
if (JSType.isSubtypeHelper(this, that)) {
return true;
}
if (that.isFunctionType()) {
FunctionType other = that.toMaybeFunctionType();
if (other.isInterface()) {
// Any function can be assigned to an interface function.
return true;
}
if (isInterface()) {
// An interface function cannot be assigned to anything.
return false;
}
// If functionA is a subtype of functionB, then their "this" types
// should be contravariant. However, this causes problems because
// of the way we enforce overrides. Because function(this:SubFoo)
// is not a subtype of function(this:Foo), our override check treats
// this as an error. Let's punt on all this for now.
// TODO(nicksantos): fix this.
boolean treatThisTypesAsCovariant =
// An interface 'this'-type is non-restrictive.
// In practical terms, if C implements I, and I has a method m,
// then any m doesn't necessarily have to C#m's 'this'
// type doesn't need to match I.
(other.typeOfThis.toObjectType() != null
&& other.typeOfThis.toObjectType().getConstructor() != null
&& other.typeOfThis.toObjectType().getConstructor().isInterface())
||
// If one of the 'this' types is covariant of the other,
// then we'll treat them as covariant (see comment above).
other.typeOfThis.isSubtype(this.typeOfThis)
|| this.typeOfThis.isSubtype(other.typeOfThis);
return treatThisTypesAsCovariant && this.call.isSubtype(other.call);
}
return getNativeType(JSTypeNative.FUNCTION_PROTOTYPE).isSubtype(that);
}
@Override
public boolean isSubtype(JSType that) {
if (JSType.isSubtypeHelper(this, that)) {
return true;
}
// Top of the record types is the empty record, or OBJECT_TYPE.
if (registry.getNativeObjectType(JSTypeNative.OBJECT_TYPE).isSubtype(that)) {
return true;
}
// A type is a subtype of a record type if it itself is a record
// type and it has at least the same members as the parent record type
// with the same types.
if (!that.isRecordType()) {
return false;
}
return RecordType.isSubtype(this, that.toMaybeRecordType());
}