org.checkerframework.framework.type.visitor

Class VisitHistory

java.lang.Object

org.checkerframework.framework.type.visitor.VisitHistory

public class VisitHistory
extends Object

IMPORTANT: DO NOT USE VisitHistory FOR VISITORS THAT UPDATE AN ANNOTATED TYPE MIRROR'S ANNOTATIONS OR YOU VIOLATE THE CONTRACT OF equals/Hashcode. THIS CLASS IS DESIGNED FOR USE WITH The DefaultTypeHierarchy AND RELATED CLASSES

VisitHistory keeps track of all visits and allows clients of this class to check whether or not they have visited a pair of AnnotatedTypeMirrors already. This is necessary in order to halt visiting on recursive bounds. Normally, this could be done using a HashSet; this class is necessary because of two properties of wildcards:

1. there are times when we encounter wildcards that have recursive bounds.
2. Since getEffectiveSuperBound and getEffectiveExtendsBound copy the bound before returning it, two calls that should return the same bound will NOT return objects that are .equals to each other. E.g.

   
    AnnotatedWildcardType wc = ...
        wc.getEffectiveSuperBound().equals(wc.getEffectiveSuperBound());
    // the above line will return false if the super bound is a wildcard
    // because two wildcards are .equals only if they are also referentially (==) equal
    // and each call to getEffectiveSuperBound returns a copy of the original bound
    

When we encounter types with property 1, property 2 ensures we cannot stop recursively comparing the bounds because the equals method will not return true when we encounter a copy of a bound we have already explored. This class defines a "Visit" inner class which consists of a pair of AnnotatedTypeMirrors. Its equalityCompare method compares AnnotatedTypeMirrors in a way that identifies wildcards that have already been compared.

Constructor Summary

Constructors

Constructor and Description
VisitHistory()

Method Summary

Modifier and Type	Method and Description
void	add(AnnotatedTypeMirror type1, AnnotatedTypeMirror type2) Add a visit for type1 and type2.
void	clear()
boolean	contains(AnnotatedTypeMirror type1, AnnotatedTypeMirror type2) Returns true if type1 and type2 (or an equivalent pair) have been passed to the add method previously.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

VisitHistory

public VisitHistory()

Method Detail

clear

public void clear()

add

public void add(AnnotatedTypeMirror type1,
                AnnotatedTypeMirror type2)

Add a visit for type1 and type2.

contains

public boolean contains(AnnotatedTypeMirror type1,
                        AnnotatedTypeMirror type2)

Returns true if type1 and type2 (or an equivalent pair) have been passed to the add method previously.

Returns:

true if an equivalent pair has already been added to the history

toString

public String toString()

Overrides:

toString in class Object