uk.co.strangeskies.reflection

Class BoundSet

java.lang.Object

uk.co.strangeskies.reflection.BoundSet

All Implemented Interfaces:

Copyable<BoundSet>, DeepCopyable<BoundSet>, Self<BoundSet>

public class BoundSet
extends java.lang.Object
implements DeepCopyable<BoundSet>

A bound set as described in chapter 18 of the Java 8 language specification. (Note that some sorts of bounds present in the document are missing from this implementation, as this API is not intended to offer the full capabilities of the compiler with respect to method references and closures.)

A bound set contains a number of InferenceVariable instances, and maintains a set of bounds between them and between other types. Types which are not inference variables, and do not mention inference variables, are considered proper types.

Note that instances of InferenceVariable which are not contained within a bound set are not considered inference variables within that context, and are treated as proper types. Inference variables are considered contained within a bound set if they were added through withInferenceVariables(Collection) , or as part of a capture conversion added through a BoundSet.IncorporationTarget belonging to that bound set.

The types of bounds which may be included in a bound set are as follows:

• Equalities between inference variables and other types, which may or may not be inference variables.
• Upper bounds on inference variables, to types which may or may not themselves be inference variables.
• Lower bounds on inference variables, from types which may or may not themselves be inference variables.
• Instances of CaptureConversion which mention inference variables.
• The bound 'false', typically meaning that a type inference attempt has failed.

An equality bound between an inference variable and a proper type is considered that inference variable's instantiation.

When you add such a bound to a bound set, it may imply the addition of further bounds, or the reduction of any number of ConstraintFormula instances into the bound set.

Bound sets, along with the processes of incorporation and reduction described, are typically used to facilitate inference of the type arguments of a generic method invocations, and to resolve overloads for such invocations between multiple methods when some are generic. This implementation therefore allows us to type check and resolve such an invocations at runtime.

We may also employ these processes towards other ends, such as type checking for data serialization formats and libraries, injection frameworks, etc., which may have slightly different rules and requirements to generic method invocation. There are also applications further outside these areas, such as inference of the type arguments of a generic supertype of a given type.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	BoundSet.IncorporationTarget Consumer of different sorts of bounds which can be a applied to inference variables, as per chapter 18 of the Java 8 language specification.

Constructor Summary

Constructors

Constructor and Description
BoundSet(BoundSet boundSet)

Method Summary

Modifier and Type	Method and Description
boolean	containsInferenceVariable(java.lang.reflect.Type type)
BoundSet	copy() Create a copy of an existing bound set.
protected BoundSet	copyInternal()
BoundSet	deepCopy(Isomorphism isomorphism) Create a copy of an existing bound set.
static BoundSet	emptyBoundSet()
InferenceVariableBounds	getBoundsOn(InferenceVariable inferenceVariable)
java.util.stream.Stream<CaptureConversion>	getCaptureConversions()
java.util.stream.Stream<InferenceVariableBounds>	getInferenceVariableBounds()
java.util.stream.Stream<InferenceVariable>	getInferenceVariables()
java.util.stream.Stream<CaptureConversion>	getRelatedCaptureConversions(java.util.Collection<? extends InferenceVariable> variables)
protected void	incorporateCaptureConversion(CaptureConversion captureConversion)
protected void	incorporateEquality(java.lang.reflect.Type first, java.lang.reflect.Type second)
protected void	incorporateFalsehood(java.lang.String message)
protected void	incorporateSubtype(java.lang.reflect.Type subtype, java.lang.reflect.Type supertype)
boolean	isEmpty()
java.lang.String	toString()
BoundSet	withBounds(BoundSet boundSet) Incorporate each bound from this given bound set into the receiver bound set.
BoundSet.IncorporationTarget	withIncorporated()
BoundSet	withInferenceVariables(java.util.Collection<? extends InferenceVariable> inferenceVariables) Add an inference variable to this bound set such that bounds can be inferred over it.
BoundSet	withInferenceVariables(InferenceVariable... inferenceVariables) Add an inference variable to this bound set such that bounds can be inferred over it.
protected BoundSet	withInferenceVariableSubstitution(Isomorphism isomorphism)
BoundSet	withInstantiations(java.util.Map<InferenceVariable,java.lang.reflect.Type> typeVariableCaptures)

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.co.strangeskies.utility.DeepCopyable

deepCopy

Methods inherited from interface uk.co.strangeskies.utility.Self

getThis

Constructor Detail

BoundSet

public BoundSet(BoundSet boundSet)

Method Detail

emptyBoundSet

public static BoundSet emptyBoundSet()

copy

public BoundSet copy()

Create a copy of an existing bound set. All the inference variables contained within the given bound set will also be contained in the new bound set, and all the bounds on them will also be copied. Subsequent modifications to the given bound set will not affect the new one, and vice versa.

Specified by:

copy in interface Copyable<BoundSet>

Returns:

a copy of the receiving instance

copyInternal

protected BoundSet copyInternal()

deepCopy

public BoundSet deepCopy(Isomorphism isomorphism)

Create a copy of an existing bound set. All the inference variables contained within the given bound set will be substituted for new inference variables in the new bound set, and all the bounds on them will be substituted for equivalent bounds. Any such inference variable substitutions made will be put into the given map.

Inference variables which already have proper instantiations may not be substituted, as this is generally unnecessary in practice and so avoiding it can save time.

Specified by:

deepCopy in interface Copyable<BoundSet>

Specified by:

deepCopy in interface DeepCopyable<BoundSet>

Parameters:

isomorphism - an isomorphism for inference variables

Returns:

A deep copy of this bound set.

withInferenceVariableSubstitution

protected BoundSet withInferenceVariableSubstitution(Isomorphism isomorphism)

incorporateFalsehood

protected void incorporateFalsehood(java.lang.String message)

incorporateEquality

protected void incorporateEquality(java.lang.reflect.Type first,
                                   java.lang.reflect.Type second)

incorporateSubtype

protected void incorporateSubtype(java.lang.reflect.Type subtype,
                                  java.lang.reflect.Type supertype)

incorporateCaptureConversion

protected void incorporateCaptureConversion(CaptureConversion captureConversion)

getInferenceVariables

public java.util.stream.Stream<InferenceVariable> getInferenceVariables()

Returns:

A set of all inference variables contained by this bound set.

isEmpty

public boolean isEmpty()

Returns:

true if the set contains no actual bounds, false otherwise

getInferenceVariableBounds

public java.util.stream.Stream<InferenceVariableBounds> getInferenceVariableBounds()

Returns:

A set of all inference variables contained by this bound set.

getBoundsOn

public InferenceVariableBounds getBoundsOn(InferenceVariable inferenceVariable)

Parameters:

inferenceVariable - An inference variable whose state we wish to query.

Returns:

A container representing the state of the given inference variable with respect to its bounds.

getCaptureConversions

public java.util.stream.Stream<CaptureConversion> getCaptureConversions()

Returns:

all capture conversion bounds contained within this bound set

getRelatedCaptureConversions

public java.util.stream.Stream<CaptureConversion> getRelatedCaptureConversions(java.util.Collection<? extends InferenceVariable> variables)

Parameters:

variables - inference variables mentioned by the capture conversions we wish to identify

Returns:

all capture conversion bounds contained within this bound set related to the given inference variables

containsInferenceVariable

public boolean containsInferenceVariable(java.lang.reflect.Type type)

Parameters:

type - the type we wish to classify

Returns:

true if the given type an inference variable within the context of this bound set, false otherwise

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

withIncorporated

public BoundSet.IncorporationTarget withIncorporated()

Returns:

A consumer through which bounds may be added to this bound set.

withBounds

public BoundSet withBounds(BoundSet boundSet)

Incorporate each bound from this given bound set into the receiver bound set. Inference variables which are contained in the given bound set will also be contained within the receiver bound set after incorporation.

Parameters:

boundSet - The bound set whose bounds we wish to incorporate.

Returns:

the derived bound set

withInferenceVariables

public BoundSet withInferenceVariables(InferenceVariable... inferenceVariables)

Add an inference variable to this bound set such that bounds can be inferred over it.

Parameters:

inferenceVariables - the inference variables to add to the bound set

Returns:

the newly added bounds, or the existing bounds

withInferenceVariables

public BoundSet withInferenceVariables(java.util.Collection<? extends InferenceVariable> inferenceVariables)

Add an inference variable to this bound set such that bounds can be inferred over it.

Parameters:

inferenceVariables - the inference variable to add to the bound set

Returns:

the newly added bounds, or the existing bounds

withInstantiations

public BoundSet withInstantiations(java.util.Map<InferenceVariable,java.lang.reflect.Type> typeVariableCaptures)