// WriteType Unification
#region Unify
/// <summary>
/// This method unifies two type expressions (this and te)
/// </summary>
/// <param name="te">The expression to be unfied with this</param>
/// <param name="unification">Indicates if the kind of unification (equivalent, incremental or override).</param>
/// <param name="previouslyUnified">To detect infinite loops. The previously unified pairs of type expressions.</param>
/// <returns>If the unification was successful</returns>
public override bool Unify(TypeExpression te, SortOfUnification unification, IList <Pair <TypeExpression, TypeExpression> > previouslyUnified)
{
// * Infinite recursion detection
Pair <TypeExpression, TypeExpression> pair = new Pair <TypeExpression, TypeExpression>(this, te);
if (previouslyUnified.Contains(pair))
{
return(true);
}
previouslyUnified.Add(pair);
bool success = false;
ArrayType at = te as ArrayType;
if (at != null)
{
success = this.arrayType.Unify(at.arrayType, unification, previouslyUnified);
}
else if (te is TypeVariable)
{
TypeVariable typeVariable = (TypeVariable)te;
if (unification != SortOfUnification.Incremental)
{
// * Incremental is commutative
success = typeVariable.Unify(this, unification, previouslyUnified);
}
else // * Array(var) should unify to Var=Array(int)
{
if (typeVariable.Substitution != null)
{
success = this.Unify(typeVariable.Substitution, unification, previouslyUnified);
}
else
{
success = false;
}
}
}
else if (te is UnionType)
{
success = te.Unify(this, unification, previouslyUnified);
}
// * Clears the type expression cache
this.ValidTypeExpression = false;
te.ValidTypeExpression = false;
return(success);
}
// WriteType Promotion
#region PromotionLevel()
/// <summary>
/// Returns a value thdat indicates a promotion level.
/// </summary>
/// <param name="type">WriteType to promotion.</param>
/// <returns>Returns a promotion value.</returns>
//public override int PromotionLevel(TypeExpression type) {
// int aux, less = -1;
// // * The same type
// if (this == type)
// return 0;
// // * Equivalent types
// if ((bool)this.AcceptOperation(new EquivalentOperation(type)))
// return 0;
// // * Field type and bounded type variable
// FieldType fieldType = TypeExpression.As<FieldType>(type);
// if (fieldType != null)
// return this.PromotionLevel(fieldType.FieldTypeExpression);
// // * WriteType variable
// TypeVariable typeVariable = type as TypeVariable;
// if (typeVariable != null) {
// if (typeVariable.Substitution != null)
// // * If the variable is bounded, the promotion is the one of its substitution
// return this.PromotionLevel(typeVariable.EquivalenceClass.Substitution);
// // * A free variable is complete promotion
// return 0;
// }
// // * Inheritance
// if (this.BaseClass == null)
// // * Object only promotes to object
// return -1;
// if ((bool)this.baseClass.AcceptOperation(new EquivalentOperation(type)))
// return 1;
// else {
// aux = this.baseClass.PromotionLevel(type);
// if (aux != -1)
// return aux + 1;
// }
// // * Interfaces
// if (this.interfaceList.Count != 0) {
// for (int i = 0; i < this.interfaceList.Count; i++) {
// if ((bool)this.interfaceList[i].AcceptOperation( new EquivalentOperation(type))) {
// if ((less > 1) || (less == -1))
// less = 1;
// }
// else {
// aux = this.interfaceList[i].PromotionLevel(type);
// if (aux != -1) {
// if ((less > (aux + 1)) || (less == -1))
// less = aux + 1;
// }
// }
// }
// }
// if (less != -1)
// return less;
// // * Union type
// UnionType unionType = TypeExpression.As<UnionType>(type);
// if (unionType != null)
// return unionType.SuperType(this);
// // * No promotion
// return -1;
//}
#endregion
// WriteType Unification
#region Unify
/// <summary>
/// This method unifies two type expressions (this and te)
/// </summary>
/// <param name="te">The expression to be unfied with this</param>
/// <param name="unification">Indicates if the kind of unification (equivalent, incremental or override).</param>
/// <param name="previouslyUnified">To detect infinite loops. The previously unified pairs of type expressions.</param>
/// <returns>If the unification was successful</returns>
public override bool Unify(TypeExpression te, SortOfUnification unification, IList <Pair <TypeExpression, TypeExpression> > previouslyUnified)
{
// * Infinite recursion detection
Pair <TypeExpression, TypeExpression> pair = new Pair <TypeExpression, TypeExpression>(this, te);
if (previouslyUnified.Contains(pair))
{
return(true);
}
previouslyUnified.Add(pair);
ClassType ct = te as ClassType;
bool success = true;
// * Class WriteType
if (ct != null)
{
// * Inheritance is taken into account
if ((int)ct.AcceptOperation(new PromotionLevelOperation(this), null) == -1)
{
return(false);
}
// * Walk upward in the tree till find the correct class
while (!(bool)ct.AcceptOperation(new EquivalentOperation(this), null))
{
ct = ct.baseClass;
}
// * Now we unify the fields
foreach (string key in this.Fields.Keys)
{
FieldType thisField = (FieldType)this.Fields[key].Type,
teField = (FieldType)ct.Fields[key].Type;
if (thisField.FieldTypeExpression is ClassTypeProxy || teField.FieldTypeExpression is ClassTypeProxy)
{
success = thisField.FieldTypeExpression.FullName.Equals(teField.FieldTypeExpression.FullName);
}
else if (!(thisField.Unify(teField, unification, previouslyUnified)))
{
success = false;
}
if (!success)
{
break;
}
}
if (success && this.baseClass != null)
{
// * The same with the base class
this.baseClass.Unify(ct.baseClass, unification, previouslyUnified);
}
// * If one of the classes is a concrete type, so it is the other
if (success)
{
this.ConcreteType = ct.ConcreteType = this.ConcreteType || ct.ConcreteType;
}
}
// * WriteType variable
else if (te is TypeVariable)
{
TypeVariable typeVariable = (TypeVariable)te;
if (unification != SortOfUnification.Incremental)
{
// * Incremental is commutative
success = typeVariable.Unify(this, unification, previouslyUnified);
}
// * Incremental unification (not commutative)
else if (typeVariable.Substitution != null)
{
// * Class(var) should unify to Var=Class(int)
success = this.Unify(typeVariable.Substitution, unification, previouslyUnified);
}
else
{
success = false;
}
}
// * Union WriteType
else if (te is UnionType)
{
success = te.Unify(this, unification, previouslyUnified);
}
// * Class WriteType Proxy
else if (te is ClassTypeProxy)
{
success = this.Unify(((ClassTypeProxy)te).RealType, unification, previouslyUnified);
}
else if (te is FieldType)
{
success = this.Unify(((FieldType)te).FieldTypeExpression, unification, previouslyUnified);
}
else
{
success = false;
}
// * Clears the type expression cache
this.ValidTypeExpression = false;
te.ValidTypeExpression = false;
return(success);
}
