private void checkVariance(
boolean covariant,
boolean contravariant,
Declaration declaration,
List<TypeParameter> errors) {
// TODO: fix this to allow reporting multiple errors!
if (getDeclaration() instanceof TypeParameter) {
TypeParameter tp = (TypeParameter) getDeclaration();
boolean ok =
tp.getDeclaration().equals(declaration)
|| ((covariant || !tp.isCovariant()) && (contravariant || !tp.isContravariant()));
if (!ok) {
// a covariant type parameter appears in a contravariant location, or
// a contravariant type parameter appears in a covariant location.
errors.add(tp);
}
} else if (getDeclaration() instanceof UnionType) {
for (ProducedType ct : getCaseTypes()) {
ct.checkVariance(covariant, contravariant, declaration, errors);
}
} else if (getDeclaration() instanceof IntersectionType) {
for (ProducedType ct : getSatisfiedTypes()) {
ct.checkVariance(covariant, contravariant, declaration, errors);
}
} else {
for (TypeParameter tp : getDeclaration().getTypeParameters()) {
ProducedType pt = getTypeArguments().get(tp);
if (pt != null) {
if (tp.isCovariant()) {
pt.checkVariance(covariant, contravariant, declaration, errors);
} else if (tp.isContravariant()) {
if (covariant | contravariant) {
pt.checkVariance(!covariant, !contravariant, declaration, errors);
} else {
// else if we are in a nonvariant position, it stays nonvariant
pt.checkVariance(covariant, contravariant, declaration, errors);
}
} else {
pt.checkVariance(false, false, declaration, errors);
}
}
}
}
}
/**
* Check that this type can appear at a position, given the variance of the position (covariant,
* contravariant, or invariant.)
*
* @param covariant true for a covariant position
* @param contravariant true for a contravariant position
* @param declaration TODO!
* @return a list of type parameters which appear in illegal positions
*/
public List<TypeParameter> checkVariance(
boolean covariant, boolean contravariant, Declaration declaration) {
List<TypeParameter> errors = new ArrayList<TypeParameter>();
checkVariance(covariant, contravariant, declaration, errors);
return errors;
}