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java.lang.Objectcom.google.javascript.rhino.jstype.JSType
com.google.javascript.rhino.jstype.UnionType
public class UnionType
The UnionType
implements a common JavaScript idiom in which the
code is specifically designed to work with multiple input types. Because
JavaScript always knows the runtime type of an object value, this is safer
than a C union.
For instance, values of the union type (String,boolean)
can be of
type String
or of type boolean
. The commutativity of the
statement is captured by making (String,boolean)
and
(boolean,String)
equal.
The implementation of this class prevents the creation of nested unions.
Nested Class Summary |
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Nested classes/interfaces inherited from class com.google.javascript.rhino.jstype.JSType |
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JSType.TypePair |
Field Summary |
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Fields inherited from class com.google.javascript.rhino.jstype.JSType |
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EMPTY_TYPE_COMPONENT, ENUMDECL, NOT_A_CLASS, NOT_A_TYPE, NOT_ENUMDECL, UNKNOWN_NAME |
Method Summary | ||
---|---|---|
JSType |
autobox()
Dereference a type for property access. |
|
boolean |
canAssignTo(JSType that)
Tests whether values of this type can be safely assigned
to values of that type. |
|
boolean |
canBeCalled()
This predicate is used to test whether a given type can be used as the 'function' in a function call. |
|
JSType |
collapseUnion()
Gets the least supertype of this that's not a union. |
|
boolean |
contains(JSType type)
A UnionType contains a given type (alternate) iff the member
vector contains it. |
|
JSType |
findPropertyType(String propertyName)
Coerces this type to an Object type, then gets the type of the property whose name is given. |
|
Iterable<JSType> |
getAlternates()
Gets the alternate types of this union type. |
|
JSType |
getLeastSupertype(JSType that)
Gets the least supertype of this and that . |
|
BooleanLiteralSet |
getPossibleToBooleanOutcomes()
Computes the set of possible outcomes of the ToBoolean predicate
for this type. |
|
JSType |
getRestrictedTypeGivenToBooleanOutcome(boolean outcome)
Computes the restricted type of this type knowing that the ToBoolean predicate has a specific value. |
|
JSType |
getRestrictedUnion(JSType type)
Returns a more restricted union type than this one, in which all
subtypes of type have been removed. |
|
JSType.TypePair |
getTypesUnderEquality(JSType that)
Computes the subset of this and that types if equality
is observed. |
|
JSType.TypePair |
getTypesUnderInequality(JSType that)
Computes the subset of this and that types if inequality
is observed. |
|
JSType.TypePair |
getTypesUnderShallowInequality(JSType that)
Computes the subset of this and that types under
shallow inequality. |
|
int |
hashCode()
|
|
boolean |
isEquivalentTo(JSType object)
Two union types are equal if they have the same number of alternates and all alternates are equal. |
|
boolean |
isNullable()
This predicate determines whether objects of this type can have the null value, and therefore can appear in contexts where
null is expected. |
|
boolean |
isObject()
Tests whether this type is an Object , or any subtype thereof. |
|
boolean |
isSubtype(JSType that)
Checks whether this is a subtype of that . |
|
boolean |
isUnknownType()
|
|
void |
matchConstraint(ObjectType constraintObj)
Modify this type so that it matches the specified type. |
|
boolean |
matchesNumberContext()
This predicate is used to test whether a given type can appear in a numeric context, such as an operand of a multiply operator. |
|
boolean |
matchesObjectContext()
This predicate is used to test whether a given type can appear in an Object context, such as the expression in a with
statement. |
|
boolean |
matchesStringContext()
This predicate is used to test whether a given type can appear in a String context, such as an operand of a string concat (+ )
operator. |
|
JSType |
restrictByNotNullOrUndefined()
If this is a union type, returns a union type that does not include the null or undefined type. |
|
boolean |
setValidator(com.google.common.base.Predicate<JSType> validator)
Certain types have constraints on them at resolution-time. |
|
TernaryValue |
testForEquality(JSType that)
Compares this and that . |
|
String |
toDebugHashCodeString()
A hash code function for diagnosing complicated issues around type-identity. |
|
UnionType |
toMaybeUnionType()
Downcasts this to a UnionType, or returns null if this is not a UnionType. |
|
|
visit(Visitor<T> visitor)
Visit this type with the given visitor. |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Method Detail |
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public Iterable<JSType> getAlternates()
public boolean matchesNumberContext()
matchesNumberContext
in class JSType
public boolean matchesStringContext()
String
context, such as an operand of a string concat (+
)
operator.
All types have at least the potential for converting to String
.
When we add externally defined types, such as a browser OM, we may choose
to add types that do not automatically convert to String
.
matchesStringContext
in class JSType
true
if not VoidType
public boolean matchesObjectContext()
Object
context, such as the expression in a with
statement.
Most types we will encounter, except notably null
, have at least
the potential for converting to Object
. Host defined objects can
get peculiar.
VOID type is included here because while it is not part of the JavaScript language, functions returning 'void' type can't be used as operands of any operator or statement.
matchesObjectContext
in class JSType
true
if the type is not NullType
or
VoidType
public JSType findPropertyType(String propertyName)
JSType
ObjectType.getPropertyType(java.lang.String)
, returns null if the property
is not found.
findPropertyType
in class JSType
null
if the current type cannot
have properties, or if the type is not found.public boolean canAssignTo(JSType that)
JSType
this
type can be safely assigned
to values of that
type.
The default implementation verifies that this
is a subtype
of that
.
canAssignTo
in class JSType
public boolean canBeCalled()
JSType
canBeCalled
in class JSType
true
if this type might be callable.public JSType autobox()
JSType
autobox
in class JSType
public JSType restrictByNotNullOrUndefined()
JSType
restrictByNotNullOrUndefined
in class JSType
public TernaryValue testForEquality(JSType that)
JSType
this
and that
.
testForEquality
in class JSType
TernaryValue.TRUE
if the comparison of values of
this
type and that
always succeed (such as
undefined
compared to null
)TernaryValue.FALSE
if the comparison of values of
this
type and that
always fails (such as
undefined
compared to number
)TernaryValue.UNKNOWN
if the comparison can succeed or
fail depending on the concrete valuespublic boolean isNullable()
null
value, and therefore can appear in contexts where
null
is expected.
isNullable
in class JSType
true
for everything but Number
and
Boolean
types.public boolean isUnknownType()
isUnknownType
in class JSType
public JSType getLeastSupertype(JSType that)
JSType
this
and that
.
The least supertype is the join (∨) or supremum of both types in the
type lattice.Examples:
number ∨ *
= *
number ∨ Object
= (number, Object)
Number ∨ Object
= Object
getLeastSupertype
in class JSType
this ∨ that
public boolean isEquivalentTo(JSType object)
isEquivalentTo
in class JSType
public int hashCode()
hashCode
in class JSType
public UnionType toMaybeUnionType()
JSType
toMaybeUnionType
in class JSType
public boolean isObject()
JSType
Object
, or any subtype thereof.
isObject
in class JSType
this <: Object
public boolean contains(JSType type)
UnionType
contains a given type (alternate) iff the member
vector contains it.
type
- The alternate which might be in this union.
true
if the alternate is in the unionpublic JSType getRestrictedUnion(JSType type)
this
one, in which all
subtypes of type
have been removed.Examples:
(number,string)
restricted by number
is
string
(null, EvalError, URIError)
restricted by
Error
is null
type
- the supertype of the types to remove from this union typepublic boolean isSubtype(JSType that)
JSType
this
is a subtype of that
.Subtyping rules:
(T<sub>1</sub>, …, T<sub>n</sub>) <: U
if and only
T<sub>k</sub> <: U
for all k ∈ 1..n
.U <: (T<sub>1</sub>, …, T<sub>n</sub>)
if and only
if U <: T<sub>k</sub>
for some index k
.O<sub>1</sub>
is a subtype
of an object O<sub>2</sub>
if it has more properties
than O<sub>2</sub>
and all common properties are
pairwise subtypes.
isSubtype
in class JSType
this <: that
public JSType getRestrictedTypeGivenToBooleanOutcome(boolean outcome)
JSType
ToBoolean
predicate has a specific value. For more information
about the ToBoolean
predicate, see
JSType.getPossibleToBooleanOutcomes()
.
getRestrictedTypeGivenToBooleanOutcome
in class JSType
outcome
- the value of the ToBoolean
predicate
public BooleanLiteralSet getPossibleToBooleanOutcomes()
JSType
ToBoolean
predicate
for this type. The ToBoolean
predicate is defined by the ECMA-262
standard, 3rd edition. Its behavior for simple types can be
summarized by the following table:
type | result |
---|---|
undefined | {false} |
null | {false} |
boolean | {true, false} |
number | {true, false} |
string | {true, false} |
Object | {true} |
getPossibleToBooleanOutcomes
in class JSType
public JSType.TypePair getTypesUnderEquality(JSType that)
JSType
this
and that
types if equality
is observed. If a value v1
of type null
is equal to a value
v2
of type (undefined,number)
, we can infer that the
type of v1
is null
and the type of v2
is
undefined
.
getTypesUnderEquality
in class JSType
this
as the first
component and the restricted type of that
as the second
element. The returned pair is never null
even though its
components may be null
public JSType.TypePair getTypesUnderInequality(JSType that)
JSType
this
and that
types if inequality
is observed. If a value v1
of type number
is not equal to a
value v2
of type (undefined,number)
, we can infer that the
type of v1
is number
and the type of v2
is
number
as well.
getTypesUnderInequality
in class JSType
this
as the first
component and the restricted type of that
as the second
element. The returned pair is never null
even though its
components may be null
public JSType.TypePair getTypesUnderShallowInequality(JSType that)
JSType
this
and that
types under
shallow inequality.
getTypesUnderShallowInequality
in class JSType
this
as the first
component and the restricted type of that
as the second
element. The returned pair is never null
even though its
components may be null
public <T> T visit(Visitor<T> visitor)
JSType
visit
in class JSType
Visitor
public String toDebugHashCodeString()
JSType
toDebugHashCodeString
in class JSType
public boolean setValidator(com.google.common.base.Predicate<JSType> validator)
JSType
@extends
annotation must be an
object. Clients should inject a validator that emits a warning
if the type does not validate, and return false.
setValidator
in class JSType
public JSType collapseUnion()
JSType
collapseUnion
in class JSType
public void matchConstraint(ObjectType constraintObj)
JSType
matchConstraint
in class JSType
|
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