Package com.google.javascript.rhino.jstype

Class JSType

java.lang.Object
com.google.javascript.rhino.jstype.JSType
Direct Known Subclasses:
AllType, BigIntType, BooleanType, NullType, NumberType, ObjectType, StringType, SymbolType, UnionType, VoidType
public abstract class JSType extends Object
Represents JavaScript value types.

Types are split into two separate families: value types and object types.

A special UnknownType exists to represent a wildcard type on which no information can be gathered. In particular, it can assign to everyone, is a subtype of everyone (and everyone is a subtype of it).

If you remove the UnknownType, the set of types in the type system forms a lattice with the isSubtype(com.google.javascript.rhino.jstype.JSType) relation defining the partial order of types. All types are united at the top of the lattice by the AllType and at the bottom by the NoType.

  • Field Details

  • 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.

    • getPropertyKind

      public JSType.HasPropertyKind getPropertyKind(String pname)
      Checks whether the property is present on the object.
      Parameters:
      pname - The property name.

    • getPropertyKind

      public JSType.HasPropertyKind getPropertyKind(String pname, boolean autobox)
      Checks whether the property is present on the object.
      Parameters:
      pname - The property name.
      autobox - Whether to check for the presents on an autoboxed type

    • hasProperty

      public final 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()

    • isBigIntObjectType

      public boolean isBigIntObjectType()

    • isBigIntValueType

      public boolean isBigIntValueType()

    • isFunctionPrototypeType

      public boolean isFunctionPrototypeType()
      Whether this is the prototype of a function.

    • isStringObjectType

      public boolean isStringObjectType()

    • isSymbolObjectType

      public boolean isSymbolObjectType()

    • isStringValueType

      public boolean isStringValueType()

    • isSymbolValueType

      public boolean isSymbolValueType()

    • 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)

    • isSymbol

      public final boolean isSymbol()

    • isBigIntOrNumber

      public final boolean isBigIntOrNumber()

    • isOnlyBigInt

      public final boolean isOnlyBigInt()
      Checks whether the type is a bigint and *only* a bigint (value or Object).

    • isArrayType

      public boolean isArrayType()

    • isReadonlyArrayType

      public boolean isReadonlyArrayType()

    • 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()

    • isSomeUnknownType

      public final boolean isSomeUnknownType()

    • isCheckedUnknownType

      public boolean isCheckedUnknownType()

    • isUnionType

      public final boolean isUnionType()

    • isRawTypeOfTemplatizedType

      public final boolean isRawTypeOfTemplatizedType()

    • 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.

    • containsReferenceAncestor

      public final boolean containsReferenceAncestor(JSType target)
      This function searchers for a type `target` in the reference chain of ProxyObjectTypes

    • isLiteralObject

      public final boolean isLiteralObject()

    • 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.

    • assertFunctionType

      public FunctionType assertFunctionType()
      Returns this object cast to FunctionType or throws an exception if it isn't a FunctionType.

    • assertObjectType

      public ObjectType assertObjectType()
      Returns this object cast to ObjectType or throws an exception if it isn't an ObjectType.

    • toMaybeFunctionType

      public static @Nullable FunctionType toMaybeFunctionType(JSType type)
      Null-safe version of toMaybeFunctionType().

    • isEnumElementType

      public final boolean isEnumElementType()

    • getEnumeratedTypeOfEnumElement

      public final @Nullable JSType getEnumeratedTypeOfEnumElement()

    • 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.

    • isNamedType

      public boolean isNamedType()

    • toMaybeNamedType

      public NamedType toMaybeNamedType()

    • isRecordType

      public boolean isRecordType()

    • isStructuralInterface

      public boolean isStructuralInterface()

    • isStructuralType

      public boolean isStructuralType()

    • toMaybeRecordType

      public RecordType toMaybeRecordType()
      Downcasts this to a RecordType, or returns null if this is not a RecordType.

    • isTemplatizedType

      public final boolean isTemplatizedType()

    • toMaybeTemplatizedType

      public TemplatizedType toMaybeTemplatizedType()
      Downcasts this to a TemplatizedType, or returns null if this is not a templatized type.

    • isTemplateType

      public final boolean isTemplateType()

    • toMaybeTemplateType

      public TemplateType toMaybeTemplateType()
      Downcasts this to a TemplateType, or returns null if this is not a template type.

    • hasAnyTemplateTypes

      public boolean hasAnyTemplateTypes()

    • getTemplateTypeMap

      public TemplateTypeMap getTemplateTypeMap()
      Returns the template type map associated with this type.

    • getTypeParameters

      public final com.google.common.collect.ImmutableList<TemplateType> getTypeParameters()
      Return, in order, the sequence of type parameters declared for this type.

      In general, this value corresponds to an element for every `@template` declaration on the type definition. It does not include template parameters from superclasses or superinterfaces.

    • getTemplateParamCount

      public int getTemplateParamCount()
      Return the number of template parameters declared for this type.

      In general, this value corresponds to the number of `@template` declarations on the type definition. It does not include template parameters from superclasses or superinterfaces.

    • mergeSupertypeTemplateTypes

      public void mergeSupertypeTemplateTypes(ObjectType other)
      Prepends the template type map associated with this type, merging in the keys and values of the specified map.

    • isObject

      public boolean isObject()
      Tests whether this type is an Object, or any subtype thereof.
      Returns:
      this <: Object

    • isObjectType

      public final boolean isObjectType()
      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).

    • isNominalConstructorOrInterface

      public final boolean isNominalConstructorOrInterface()
      Whether this type is the original constructor of a nominal type. Does not include structural constructors.

    • isNativeObjectType

      public boolean isNativeObjectType()

    • loosenTypecheckingDueToForwardReferencedSupertype

      public boolean loosenTypecheckingDueToForwardReferencedSupertype()
      During type definition, was one of the supertypes of this type a forward reference?

      This is a hack to work around the fact that inheritance chains and template types aren't wired up correctly when this happens, which causes various false positives in checks. The known bugs associated are b/145145406, b/144327372, and b/132980305.

      This method should only be used to suppress potential false positives caused by one of the above bugs, in the case where we think suppressing typechecking is preferable to emitting a false positive.

    • 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 (i.e. not a constructor, nominal interface, or record interface), or a named type that points to such a type.

    • equals

      public final boolean equals(@Nullable Object other)
      Overrides:
      equals in class Object

    • 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 EqMethod for more info.

    • areSimilar

      public static final boolean areSimilar(@Nullable JSType first, @Nullable JSType second)
      Whether the first type is meaningfully same as second type for the purposes of data flow analysis.

    • hashCode

      public final int hashCode()
      Calculates a hash of the object as per Object.hashCode().

      This method is unsafe for multi-threaded use. The implementation mutates instance state to prevent recursion and therefore expects sole access.

      Overrides:
      hashCode in class Object

    • 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.

    • matchesSymbolContext

      public boolean matchesSymbolContext()
      This predicate is used to test whether a given type can appear in a symbol context such as property access.

    • 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 final @Nullable 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.

    • findPropertyTypeWithoutConsideringTemplateTypes

      @ForOverride protected @Nullable JSType findPropertyTypeWithoutConsideringTemplateTypes(String propertyName)
      Looks up a property on this type, but without properly replacing any templates in the result.

      Subclasses can override this if they need more complicated logic for property lookup than just autoboxing to an object.

      This is only for use by findPropertyType(JSType). Call that method instead if you need to lookup a property on a random JSType

    • 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 final 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.

    • isBoxableScalar

      public boolean isBoxableScalar()

    • toObjectType

      public @Nullable 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()
      Dereferences a type for property access. Filters null/undefined and autoboxes the resulting type. Never returns null.

    • dereference

      public final @Nullable ObjectType dereference()
      Dereferences a type for property access.

      Filters null/undefined, autoboxes the resulting type, and returns it iff it's an object. If not an object, returns null.

    • 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 Tri testForEquality(JSType that)
      Compares this and that.
      Returns:
      • Tri.TRUE if the comparison of values of this type and that always succeed (such as undefined compared to null)
      • Tri.FALSE if the comparison of values of this type and that always fails (such as undefined compared to number)
      • Tri.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.

    • isVoidable

      public boolean isVoidable()
      Tests whether this type is voidable.

    • isExplicitlyVoidable

      public boolean isExplicitlyVoidable()
      Tests whether this type explicitly allows undefined, as opposed to ? or *. This is required for a property to be optional.

    • 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

    • getRestrictedTypeGivenOutcome

      public JSType getRestrictedTypeGivenOutcome(Outcome 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, 3rd edition. Its behavior for simple types can be summarized by the following table:
      ToBoolean results by input type
      typeresult
      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 final 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

    • getUnionMembers

      public @Nullable Iterable<JSType> getUnionMembers()

    • restrictByNotNullOrUndefined

      public JSType restrictByNotNullOrUndefined()
      If this is a union type, returns a union type that does not include the null or undefined type.

    • restrictByNotUndefined

      public JSType restrictByNotUndefined()
      If this is a union type, returns a union type that does not include the undefined type.

    • restrictByNotNull

      public JSType restrictByNotNull()
      If this is a union type, returns a union type that does not include the null type.

    • isSubtypeWithoutStructuralTyping

      public final boolean isSubtypeWithoutStructuralTyping(JSType supertype)
      the logic of this method is similar to isSubtype, except that it does not perform structural interface matching

      This function is added for disambiguate properties, and is deprecated for the other use cases.

    • isSubtype

      public final boolean isSubtype(JSType supertype)
      Checks whether this is a subtype of that.

      Note this function also returns true if this type structurally matches the protocol define by that type (if that type is an interface function type)

      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
        (T1, …, Tn) <: U if and only Tk <: 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 <: (T1, …, Tn) if and only if U <: Tk for some index k.
      • (objects) — an Object O1 is a subtype of an object O2 if it has more properties than O2 and all common properties are pairwise subtypes.
      Returns:
      this <: that

    • isSubtype

      @InlineMe(replacement="this.isSubtypeOf(supertype, mode)") @Deprecated public final boolean isSubtype(JSType supertype, JSType.SubtypingMode mode)
      Deprecated.
      Prefer isSubtype(JSType) instead.

    • isSubtypeOf

      public final boolean isSubtypeOf(JSType supertype)

    • isSubtypeOf

      public final boolean isSubtypeOf(JSType supertype, JSType.SubtypingMode mode)

    • 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:

    • resolve

      public final JSType resolve(ErrorReporter reporter)
      Resolve this type in the given scope.

      The returned value must be equal to this, as defined by equals(java.lang.Object). 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()
      Returns whether the type has undergone resolution.

      A value of true does not indicate that resolution was successful, only that it was attempted and has finished.

    • isSuccessfullyResolved

      public final boolean isSuccessfullyResolved()
      Returns whether the type has undergone resolution and resolved to a "useful" type.

    • isUnsuccessfullyResolved

      public final boolean isUnsuccessfullyResolved()
      Returns whether the type has undergone resolution and resolved to a "useless" type.

    • 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

    • toAnnotationString

      public final String toAnnotationString(JSType.Nullability nullability)

    • 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).

    • toMaybeObjectType

      public ObjectType toMaybeObjectType()