Class JSType

Method Details

• getJSDocInfo

  public JSDocInfo getJSDocInfo()

  Gets the docInfo for this type. By default, documentation cannot be attached to arbitrary types. This must be overridden for programmer-defined types.

• getDisplayName

  public String getDisplayName()

  Returns a user meaningful label for the JSType instance. For example, Functions and Enums will return their declaration name (if they have one). Some types will not have a meaningful display name. Calls to hasDisplayName() will return true IFF getDisplayName() will return null or a zero length string.

  Returns:

  the display name of the type, or null if one is not available

• hasDisplayName

  public boolean hasDisplayName()

  Returns:

  true if the JSType has a user meaningful label.

• hasProperty

  public boolean hasProperty(String pname)

  Checks whether the property is present on the object.

  Parameters:

  pname - The property name.

• isNoType

  public boolean isNoType()

• isNoResolvedType

  public boolean isNoResolvedType()

• isNoObjectType

  public boolean isNoObjectType()

• isEmptyType

  public final boolean isEmptyType()

• isNumberObjectType

  public boolean isNumberObjectType()

• isNumberValueType

  public boolean isNumberValueType()

• isFunctionPrototypeType

  public boolean isFunctionPrototypeType()

  Whether this is the prototype of a function.

• isStringObjectType

  public boolean isStringObjectType()

• isStringValueType

  public boolean isStringValueType()

• isString

  public final boolean isString()

  Tests whether the type is a string (value or Object).

  Returns:

  this <: (String, string)

• isNumber

  public final boolean isNumber()

  Tests whether the type is a number (value or Object).

  Returns:

  this <: (Number, number)

• isArrayType

  public boolean isArrayType()

• isBooleanObjectType

  public boolean isBooleanObjectType()

• isBooleanValueType

  public boolean isBooleanValueType()

• isRegexpType

  public boolean isRegexpType()

• isDateType

  public boolean isDateType()

• isNullType

  public boolean isNullType()

• isVoidType

  public boolean isVoidType()

• isAllType

  public boolean isAllType()

• isUnknownType

  public boolean isUnknownType()

• isCheckedUnknownType

  public boolean isCheckedUnknownType()

• isUnionType

  public final boolean isUnionType()

• isStruct

  public boolean isStruct()

  Returns true iff this can be a struct. UnionType overrides the method, assume this is not a union here.

• isDict

  public boolean isDict()

  Returns true iff this can be a dict. UnionType overrides the method, assume this is not a union here.

• toMaybeUnionType

  public UnionType toMaybeUnionType()

  Downcasts this to a UnionType, or returns null if this is not a UnionType. Named in honor of Haskell's Maybe type constructor.

• isGlobalThisType

  public final boolean isGlobalThisType()

  Returns true if this is a global this type.

• isFunctionType

  public final boolean isFunctionType()

  Returns true if toMaybeFunctionType returns a non-null FunctionType.

• toMaybeFunctionType

  public FunctionType toMaybeFunctionType()

  Downcasts this to a FunctionType, or returns null if this is not a function. For the purposes of this function, we define a MaybeFunctionType as any type in the sub-lattice { x | LEAST_FUNCTION_TYPE <= x <= GREATEST_FUNCTION_TYPE } This definition excludes bottom types like NoType and NoObjectType. This definition is somewhat arbitrary and axiomatic, but this is the definition that makes the most sense for the most callers.

• toMaybeFunctionType

  public static FunctionType toMaybeFunctionType(JSType type)

  Null-safe version of toMaybeFunctionType().

• isEnumElementType

  public final boolean isEnumElementType()

• toMaybeEnumElementType

  public EnumElementType toMaybeEnumElementType()

  Downcasts this to an EnumElementType, or returns null if this is not an EnumElementType.

• isEnumType

  public boolean isEnumType()

• toMaybeEnumType

  public EnumType toMaybeEnumType()

  Downcasts this to an EnumType, or returns null if this is not an EnumType.

• isRecordType

  public boolean isRecordType()

• isTemplatizedType

  public final boolean isTemplatizedType()

• toMaybeTemplatizedType

  public TemplatizedType toMaybeTemplatizedType()

  Downcasts this to a TemplatizedType, or returns null if this is not a function.

• toMaybeTemplatizedType

  public static TemplatizedType toMaybeTemplatizedType(JSType type)

  Null-safe version of toMaybeTemplatizedType().

• isTemplateType

  public final boolean isTemplateType()

• toMaybeTemplateType

  public TemplateType toMaybeTemplateType()

  Downcasts this to a TemplateType, or returns null if this is not a function.

• toMaybeTemplateType

  public static TemplateType toMaybeTemplateType(JSType type)

  Null-safe version of toMaybeTemplateType().

• hasAnyTemplateTypes

  public boolean hasAnyTemplateTypes()

• getTemplateTypeMap

  public TemplateTypeMap getTemplateTypeMap()

  Returns the template type map associated with this type.

• isObject

  public boolean isObject()

  Tests whether this type is an Object, or any subtype thereof.

  Returns:

  this <: Object

• isConstructor

  public boolean isConstructor()

  Whether this type is a FunctionType that is a constructor or a named type that points to such a type.

• isNominalType

  public boolean isNominalType()

  Whether this type is a nominal type (a named instance object or a named enum).

• isNominalConstructor

  public final boolean isNominalConstructor()

  Whether this type is the original constructor of a nominal type. Does not include structural constructors.

• isInstanceType

  public boolean isInstanceType()

  Whether this type is an Instance object of some constructor. Does not necessarily mean this is an InstanceObjectType.

• isInterface

  public boolean isInterface()

  Whether this type is a FunctionType that is an interface or a named type that points to such a type.

• isOrdinaryFunction

  public boolean isOrdinaryFunction()

  Whether this type is a FunctionType that is an ordinary function or a named type that points to such a type.

• isEquivalentTo

  public final boolean isEquivalentTo(JSType that)

  Checks if two types are equivalent.

• isInvariant

  public final boolean isInvariant(JSType that)

  Checks if two types are invariant.

  See Also:

  • EquivalenceMethod

• differsFrom

  public final boolean differsFrom(JSType that)

  Whether this type is meaningfully different from that type for the purposes of data flow analysis. This is a trickier check than pure equality, because it has to properly handle unknown types. See EquivalenceMethod for more info.

  See Also:

  • Unknown unknowns

• isEquivalent

  public static boolean isEquivalent(JSType typeA, JSType typeB)

• equals

  public boolean equals(Object jsType)

  Overrides:

  equals in class Object

• hashCode

  public int hashCode()

  Overrides:

  hashCode in class Object

• matchesInt32Context

  public final boolean matchesInt32Context()

  This predicate is used to test whether a given type can appear in a 'Int32' context. This context includes, for example, the operands of a bitwise or operator. Since we do not currently support integer types, this is a synonym for Number.

• matchesUint32Context

  public final boolean matchesUint32Context()

  This predicate is used to test whether a given type can appear in a 'Uint32' context. This context includes the right-hand operand of a shift operator.

• matchesNumberContext

  public 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.

• matchesStringContext

  public 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. 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.

• matchesObjectContext

  public 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. Most types we will encounter, except notably null, have at least the potential for converting to Object. Host defined objects can get peculiar.

• findPropertyType

  public JSType findPropertyType(String propertyName)

  Coerces this type to an Object type, then gets the type of the property whose name is given. Unlike ObjectType.getPropertyType(java.lang.String), returns null if the property is not found.

  Returns:

  The property's type. null if the current type cannot have properties, or if the type is not found.

• canBeCalled

  public boolean canBeCalled()

  This predicate is used to test whether a given type can be used as the 'function' in a function call.

  Returns:

  true if this type might be callable.

• canCastTo

  public boolean canCastTo(JSType that)

  Tests whether values of this type can be safely assigned to values of that type.

  The default implementation verifies that this is a subtype of that.

• autoboxesTo

  public JSType autoboxesTo()

  Turn a scalar type to the corresponding object type.

  Returns:

  the auto-boxed type or null if this type is not a scalar.

• unboxesTo

  public JSType unboxesTo()

  Turn an object type to its corresponding scalar type.

  Returns:

  the unboxed type or null if this type does not unbox.

• toObjectType

  public ObjectType toObjectType()

  Casts this to an ObjectType, or returns null if this is not an ObjectType. If this is a scalar type, it will *not* be converted to an object type. If you want to simulate JS autoboxing or dereferencing, you should use autoboxesTo() or dereference().

• autobox

  public JSType autobox()

  Dereference a type for property access. Filters null/undefined and autoboxes the resulting type. Never returns null.

• dereference

  public final ObjectType dereference()

  Dereference a type for property access. Filters null/undefined, autoboxes the resulting type, and returns it iff it's an object.

• canTestForEqualityWith

  public final boolean canTestForEqualityWith(JSType that)

  Tests whether this and that are meaningfully comparable. By meaningfully, we mean compatible types that do not lead to step 22 of the definition of the Abstract Equality Comparison Algorithm (11.9.3, page 55–56) of the ECMA-262 specification.

• testForEquality

  public TernaryValue testForEquality(JSType that)

  Compares this and that.

  Returns:

  • 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 values

• canTestForShallowEqualityWith

  public final boolean canTestForShallowEqualityWith(JSType that)

  Tests whether this and that are meaningfully comparable using shallow comparison. By meaningfully, we mean compatible types that are not rejected by step 1 of the definition of the Strict Equality Comparison Algorithm (11.9.6, page 56–57) of the ECMA-262 specification.

• isNullable

  public boolean isNullable()

  Tests whether this type is nullable.

• collapseUnion

  public JSType collapseUnion()

  Gets the least supertype of this that's not a union.

• getLeastSupertype

  public JSType getLeastSupertype(JSType that)

  Gets the least supertype of 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

  Returns:

  this ∨ that

• getGreatestSubtype

  public JSType getGreatestSubtype(JSType that)

  Gets the greatest subtype of this and that. The greatest subtype is the meet (∧) or infimum of both types in the type lattice.

  Examples

  • Number ∧ Any = Any
  • number ∧ Object = Any
  • Number ∧ Object = Number

  Returns:

  this ∨ that

• getRestrictedTypeGivenToBooleanOutcome

  public JSType getRestrictedTypeGivenToBooleanOutcome(boolean outcome)

  Computes the restricted type of this type knowing that the ToBoolean predicate has a specific value. For more information about the ToBoolean predicate, see getPossibleToBooleanOutcomes().

  Parameters:

  outcome - the value of the ToBoolean predicate

  Returns:

  the restricted type, or the Any Type if the underlying type could not have yielded this ToBoolean value TODO(user): Move this method to the SemanticRAI and use the visit method of types to get the restricted type.

• getPossibleToBooleanOutcomes

  public abstract BooleanLiteralSet getPossibleToBooleanOutcomes()

  Computes the set of possible outcomes of the ToBoolean predicate for this type. The ToBoolean predicate is defined by the ECMA-262 standard, 3^rd 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}

  Returns:

  the set of boolean literals for this type

• getTypesUnderEquality

  public JSType.TypePair getTypesUnderEquality(JSType that)

  Computes the subset of 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.

  Returns:

  a pair containing the restricted type of 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

• getTypesUnderInequality

  public JSType.TypePair getTypesUnderInequality(JSType that)

  Computes the subset of 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.

  Returns:

  a pair containing the restricted type of 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

• getTypesUnderShallowEquality

  public JSType.TypePair getTypesUnderShallowEquality(JSType that)

  Computes the subset of this and that types under shallow equality.

  Returns:

  a pair containing the restricted type of 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.

• getTypesUnderShallowInequality

  public JSType.TypePair getTypesUnderShallowInequality(JSType that)

  Computes the subset of this and that types under shallow inequality.

  Returns:

  A pair containing the restricted type of 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

• restrictByNotNullOrUndefined

  public JSType restrictByNotNullOrUndefined()

  If this is a union type, returns a union type that does not include the null or undefined type.

• isSubtype

  public boolean isSubtype(JSType that)

  Checks whether this is a subtype of that.

  Subtyping rules:

  • (unknown) — every type is a subtype of the Unknown type.
  • (no) — the No type is a subtype of every type.
  • (no-object) — the NoObject type is a subtype of every object type (i.e. subtypes of the Object type).
  • (ref) — a type is a subtype of itself.
  • (union-l) — A union type is a subtype of a type U if all the union type's constituents are a subtype of U. Formally
    (T<sub>1</sub>, &hellip;, T<sub>n</sub>) &lt;: U if and only T<sub>k</sub> &lt;: U for all k ∈ 1..n.
  • (union-r) — A type U is a subtype of a union type if it is a subtype of one of the union type's constituents. Formally
    U &lt;: (T<sub>1</sub>, &hellip;, T<sub>n</sub>) if and only if U &lt;: T<sub>k</sub> for some index k.
  • (objects) — an Object 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.

  Returns:

  this <: that

• visit

  public abstract <T> T visit(Visitor<T> visitor)

  Visit this type with the given visitor.

  Returns:

  the value returned by the visitor

  See Also:

  • Visitor

• forceResolve

  public final JSType forceResolve(ErrorReporter t, StaticScope<JSType> scope)

  Force this type to resolve, even if the registry is in a lazy resolving mode.

  See Also:

  • resolve(com.google.javascript.rhino.ErrorReporter, com.google.javascript.rhino.jstype.StaticScope<com.google.javascript.rhino.jstype.JSType>)

• resolve

  public final JSType resolve(ErrorReporter t, StaticScope<JSType> scope)

  Resolve this type in the given scope. The returned value must be equal to this, as defined by isEquivalentTo(com.google.javascript.rhino.jstype.JSType). It may or may not be the same object. This method may modify the internal state of this, as long as it does so in a way that preserves Object equality. For efficiency, we should only resolve a type once per compilation job. For incremental compilations, one compilation job may need the artifacts from a previous generation, so we will eventually need a generational flag instead of a boolean one.

• isResolved

  public final boolean isResolved()

  Whether the type has been resolved.

• clearResolved

  public final void clearResolved()

  Clears the resolved field.

• setValidator

  public boolean setValidator(com.google.common.base.Predicate<JSType> validator)

  Certain types have constraints on them at resolution-time. For example, a type in an @extends annotation must be an object. Clients should inject a validator that emits a warning if the type does not validate, and return false.

• toString

  public String toString()

  A string representation of this type, suitable for printing in warnings.

  Overrides:

  toString in class Object

• toDebugHashCodeString

  public String toDebugHashCodeString()

  A hash code function for diagnosing complicated issues around type-identity.

• toAnnotationString

  public final String toAnnotationString()

  A string representation of this type, suitable for printing in type annotations at code generation time.

• matchConstraint

  public void matchConstraint(JSType constraint)

  Modify this type so that it matches the specified type. This is useful for reverse type-inference, where we want to infer that an object literal matches its constraint (much like how the java compiler does reverse-inference to figure out generics).

  Parameters:

  constraint -