/** Check that the assignment to a field is correct. */
protected void checkFieldAssign(
FlowGraph graph, FieldAssign a, DataFlowItem dfIn, DataFlowItem dfOut)
throws SemanticException {
Field f = (Field) a.left();
FieldInstance fi = f.fieldInstance();
if (fi.flags().isFinal()) {
if ((currCBI.currCodeDecl instanceof ConstructorDecl
|| currCBI.currCodeDecl instanceof Initializer)
&& isFieldsTargetAppropriate(f)) {
// we are in a constructor or initializer block and
// if the field is static then the target is the class
// at hand, and if it is not static then the
// target of the field is this.
// So a final field in this situation can be
// assigned to at most once.
MinMaxInitCount initCount = (MinMaxInitCount) dfOut.initStatus.get(fi);
if (InitCount.MANY.equals(initCount.getMax())) {
throw new SemanticException(
"field \"" + fi.name() + "\" might already have been assigned to", a.position());
}
} else {
// not in a constructor or intializer, or the target is
// not appropriate. So we cannot assign
// to a final field at all.
throw new SemanticException(
"Cannot assign a value " + "to final field \"" + fi.name() + "\"", a.position());
}
}
}
/**
* Determine if we are interested in this field on the basis of the target of the field. To wit,
* if the field is static, then the target of the field must be the current class; if the field is
* not static then the target must be "this".
*/
protected boolean isFieldsTargetAppropriate(Field f) {
if (f.fieldInstance().flags().isStatic()) {
ClassType containingClass = (ClassType) currCBI.currCodeDecl.codeInstance().container();
return containingClass.equals(f.fieldInstance().container());
} else {
return (f.target() instanceof Special && Special.THIS.equals(((Special) f.target()).kind()));
}
}
/** Perform the appropriate flow operations for assignment to a field */
protected Map flowFieldAssign(
DataFlowItem inItem, FlowGraph graph, FieldAssign a, Set succEdgeKeys) {
Field f = (Field) a.left();
FieldInstance fi = f.fieldInstance();
if (fi.flags().isFinal() && isFieldsTargetAppropriate(f)) {
// this field is final and the target for this field is
// appropriate for what we are interested in.
Map m = new HashMap(inItem.initStatus);
MinMaxInitCount initCount = (MinMaxInitCount) m.get(fi);
// initCount may be null if the field is defined in an
// outer class.
if (initCount != null) {
initCount =
new MinMaxInitCount(initCount.getMin().increment(), initCount.getMax().increment());
m.put(fi, initCount);
return itemToMap(new DataFlowItem(m), succEdgeKeys);
}
}
return null;
}
protected NodeVisitor enterCall(Node n) throws SemanticException {
if (n instanceof FieldDecl) {
FieldDecl fd = (FieldDecl) n;
FwdReferenceChecker frc = (FwdReferenceChecker) this.copy();
frc.inInitialization = true;
frc.inStaticInit = fd.flags().flags().isStatic();
frc.declaredFields = new HashSet<FieldDef>(declaredFields);
declaredFields.add(fd.fieldDef());
return frc;
} else if (n instanceof Initializer) {
FwdReferenceChecker frc = (FwdReferenceChecker) this.copy();
frc.inInitialization = true;
frc.inStaticInit = ((Initializer) n).flags().flags().isStatic();
return frc;
} else if (n instanceof FieldAssign) {
FwdReferenceChecker frc = (FwdReferenceChecker) this.copy();
return frc;
} else if (n instanceof Field) {
if (inInitialization) {
// we need to check if this is an illegal fwd reference.
Field f = (Field) n;
// an illegal fwd reference if a usage of an instance
// (resp. static) field occurs in an instance (resp. static)
// initialization, and the innermost enclosing class or
// interface of the usage is the same as the container of
// the field, and we have not yet seen the field declaration.
//
// In addition, if a field is not accessed as a simple name,
// then all is ok
ClassType currentClass = context().currentClass();
StructType fContainer = f.fieldInstance().container();
if (inStaticInit == f.fieldInstance().flags().isStatic()
&& currentClass.typeEquals(fContainer, context)
&& !declaredFields.contains(f.fieldInstance().def())
&& f.isTargetImplicit()) {
throw new SemanticException("Illegal forward reference", f.position());
}
}
}
return this;
}
public Field createField(DataInputStream in) throws IOException {
Field f = new Field(in, this);
f.initialize();
return f;
}