/**
* Return the greatest lower bound of two types. That is, return the largest type that is a
* subtype of both inputs.
*/
public JReferenceType strongerType(JReferenceType type1, JReferenceType type2) {
if (type1 == type2) {
return type1;
}
if (type1 instanceof JNullType || type2 instanceof JNullType) {
return JNullType.INSTANCE;
}
if (type1 instanceof JNonNullType != type2 instanceof JNonNullType) {
// If either is non-nullable, the result should be non-nullable.
return strongerType(type1.getNonNull(), type2.getNonNull());
}
if (typeOracle.canTriviallyCast(type1, type2)) {
return type1;
}
if (typeOracle.canTriviallyCast(type2, type1)) {
return type2;
}
// cannot determine a strong type, just return the first one (this makes two
// "unrelated" interfaces work correctly in TypeTightener
return type1;
}
public boolean isJavaScriptObject(JType type) {
if (type instanceof JReferenceType && typeSpecialJavaScriptObject != null) {
return typeOracle.canTriviallyCast((JReferenceType) type, typeSpecialJavaScriptObject);
}
return false;
}
/**
* Return the least upper bound of two types. That is, the smallest type that is a supertype of
* both types.
*/
public JReferenceType generalizeTypes(JReferenceType type1, JReferenceType type2) {
if (type1 == type2) {
return type1;
}
if (type1 instanceof JNonNullType && type2 instanceof JNonNullType) {
// Neither can be null.
type1 = type1.getUnderlyingType();
type2 = type2.getUnderlyingType();
return generalizeTypes(type1, type2).getNonNull();
} else if (type1 instanceof JNonNullType) {
// type2 can be null, so the result can be null
type1 = type1.getUnderlyingType();
} else if (type2 instanceof JNonNullType) {
// type1 can be null, so the result can be null
type2 = type2.getUnderlyingType();
}
assert !(type1 instanceof JNonNullType);
assert !(type2 instanceof JNonNullType);
int classify1 = classifyType(type1);
int classify2 = classifyType(type2);
if (classify1 == IS_NULL) {
return type2;
}
if (classify2 == IS_NULL) {
return type1;
}
if (classify1 == classify2) {
// same basic kind of type
if (classify1 == IS_INTERFACE) {
if (typeOracle.canTriviallyCast(type1, type2)) {
return type2;
}
if (typeOracle.canTriviallyCast(type2, type1)) {
return type1;
}
// unrelated
return typeJavaLangObject;
} else if (classify1 == IS_ARRAY) {
JArrayType aType1 = (JArrayType) type1;
JArrayType aType2 = (JArrayType) type2;
int dims1 = aType1.getDims();
int dims2 = aType2.getDims();
int minDims = Math.min(dims1, dims2);
/*
* At a bare minimum, any two arrays generalize to an Object array with
* one less dim than the lesser of the two; that is, int[][][][] and
* String[][][] generalize to Object[][]. If minDims is 1, then they
* just generalize to Object.
*/
JReferenceType minimalGeneralType;
if (minDims > 1) {
minimalGeneralType = getTypeArray(typeJavaLangObject, minDims - 1);
} else {
minimalGeneralType = typeJavaLangObject;
}
if (dims1 == dims2) {
// Try to generalize by leaf types
JType leafType1 = aType1.getLeafType();
JType leafType2 = aType2.getLeafType();
if (!(leafType1 instanceof JReferenceType) || !(leafType2 instanceof JReferenceType)) {
return minimalGeneralType;
}
/*
* Both are reference types; the result is the generalization of the
* leaf types combined with the number of dims; that is, Foo[] and
* Bar[] generalize to X[] where X is the generalization of Foo and
* Bar.
*/
JReferenceType leafRefType1 = (JReferenceType) leafType1;
JReferenceType leafRefType2 = (JReferenceType) leafType2;
/**
* Never generalize arrays to arrays of {@link JNonNullType} as null array initialization
* is not accounted for in {@link TypeTightener}.
*/
JReferenceType leafGeneralization =
generalizeTypes(leafRefType1, leafRefType2).getUnderlyingType();
return getTypeArray(leafGeneralization, dims1);
} else {
// Conflicting number of dims
// int[][] and Object[] generalize to Object[]
JArrayType lesser = dims1 < dims2 ? aType1 : aType2;
if (lesser.getLeafType() == typeJavaLangObject) {
return lesser;
}
// Totally unrelated
return minimalGeneralType;
}
} else {
assert (classify1 == IS_CLASS);
JClassType class1 = (JClassType) type1;
JClassType class2 = (JClassType) type2;
/*
* see how far each type is from object; walk the one who's farther up
* until they're even; then walk them up together until they meet (worst
* case at Object)
*/
int distance1 = countSuperTypes(class1);
int distance2 = countSuperTypes(class2);
for (; distance1 > distance2; --distance1) {
class1 = class1.getSuperClass();
}
for (; distance1 < distance2; --distance2) {
class2 = class2.getSuperClass();
}
while (class1 != class2) {
class1 = class1.getSuperClass();
class2 = class2.getSuperClass();
}
return class1;
}
} else {
// different kinds of types
int lesser = Math.min(classify1, classify2);
int greater = Math.max(classify1, classify2);
JReferenceType tLesser = classify1 < classify2 ? type1 : type2;
JReferenceType tGreater = classify1 > classify2 ? type1 : type2;
if (lesser == IS_INTERFACE && greater == IS_CLASS) {
// just see if the class implements the interface
if (typeOracle.canTriviallyCast(tGreater, tLesser)) {
return tLesser;
}
// unrelated
return typeJavaLangObject;
} else if (greater == IS_ARRAY
&& ((tLesser == typeJavaLangCloneable) || (tLesser == typeJavaIoSerializable))) {
return tLesser;
} else {
// unrelated: the best commonality between an interface and array, or
// between an array and a class is Object
return typeJavaLangObject;
}
}
}
