`@typescript-eslint/type-utils`

Type utilities for working with TypeScript types ✨

This package contains public utilities for working with TypeScript types. Rules declared in @typescript-eslint/eslint-plugin use these utility functions.

The utilities in this package are both:

More generally ESLint-focused than the broad TypeScript utilities in ts-api-utils
Separated from @typescript-eslint/utils so that that package does not require a dependency on typescript

tip

See Custom Rules for documentation on creating your own custom ESLint rules for TypeScript code.

The following documentation is auto-generated from source code.

Functions

containsAllTypesByName()

function containsAllTypesByName(
   type, 
   allowAny, 
   allowedNames, 
   matchAnyInstead): boolean

Parameters

Parameter	Type	Default value	Description
`type`	`Type`	`undefined`	Type being checked by name.
`allowAny`	`boolean`	`undefined`	Whether to consider `any` and `unknown` to match.
`allowedNames`	`Set`<`string`>	`undefined`	Symbol names checking on the type.
`matchAnyInstead`	`boolean`	`false`	Whether to instead just check if any parts match, rather than all parts.

Returns

boolean

Whether the type is, extends, or contains the allowed names (or all matches the allowed names, if mustMatchAll is true).

Defined in

containsAllTypesByName.ts:13

discriminateAnyType()

function discriminateAnyType(
   type, 
   checker, 
   program, 
   tsNode): AnyType

Parameters

Parameter	Type
`type`	`Type`
`checker`	`TypeChecker`
`program`	`Program`
`tsNode`	`Node`

Returns

AnyType

AnyType.Any if the type is any, AnyType.AnyArray if the type is any[] or readonly any[], AnyType.PromiseAny if the type is Promise<any>, otherwise it returns AnyType.Safe.

Defined in

predicates.ts:121

getConstrainedTypeAtLocation()

function getConstrainedTypeAtLocation(services, node): ts.Type

Resolves the given node's type. Will resolve to the type's generic constraint, if it has one.

Parameters

Parameter	Type
`services`	`ParserServicesWithTypeInformation`
`node`	`Node`

Returns

ts.Type

Defined in

getConstrainedTypeAtLocation.ts:10

getContextualType()

function getContextualType(checker, node): ts.Type | undefined

Returns the contextual type of a given node. Contextual type is the type of the target the node is going into. i.e. the type of a called function's parameter, or the defined type of a variable declaration

Parameters

Parameter	Type
`checker`	`TypeChecker`
`node`	`Expression`

Returns

ts.Type | undefined

Defined in

getContextualType.ts:8

getDeclaration()

function getDeclaration(services, node): ts.Declaration | null

Gets the declaration for the given variable

Parameters

Parameter	Type
`services`	`ParserServicesWithTypeInformation`
`node`	`Node`

Returns

ts.Declaration | null

Defined in

getDeclaration.ts:10

getSourceFileOfNode()

function getSourceFileOfNode(node): ts.SourceFile

Gets the source file for a given node

Parameters

Parameter	Type
`node`	`Node`

Returns

ts.SourceFile

Defined in

getSourceFileOfNode.ts:6

getTypeFlags()

function getTypeFlags(type): ts.TypeFlags

Gets all of the type flags in a type, iterating through unions automatically.

Parameters

Parameter	Type
`type`	`Type`

Returns

ts.TypeFlags

Defined in

typeFlagUtils.ts:9

getTypeName()

function getTypeName(typeChecker, type): string

Get the type name of a given type.

Parameters

Parameter	Type	Description
`typeChecker`	`TypeChecker`	The context sensitive TypeScript TypeChecker.
`type`	`Type`	The type to get the name of.

Returns

string

Defined in

getTypeName.ts:8

getTypeOfPropertyOfName()

function getTypeOfPropertyOfName(
   checker, 
   type, 
   name, 
   escapedName?): ts.Type | undefined

Parameters

Parameter	Type
`checker`	`TypeChecker`
`type`	`Type`
`name`	`string`
`escapedName`?	`__String`

Returns

ts.Type | undefined

Defined in

propertyTypes.ts:3

getTypeOfPropertyOfType()

function getTypeOfPropertyOfType(
   checker, 
   type, 
   property): ts.Type | undefined

Parameters

Parameter	Type
`checker`	`TypeChecker`
`type`	`Type`
`property`	`Symbol`

Returns

ts.Type | undefined

Defined in

propertyTypes.ts:25

isBuiltinSymbolLike()

function isBuiltinSymbolLike(
   program, 
   type, 
   symbolName): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`
`symbolName`	`string` \| `string`[]

Returns

boolean

Defined in

builtinSymbolLikes.ts:121

isBuiltinSymbolLikeRecurser()

function isBuiltinSymbolLikeRecurser(
   program, 
   type, 
   predicate): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`
`predicate`	(`subType`) => `null` \| `boolean`

Returns

boolean

Defined in

builtinSymbolLikes.ts:147

isBuiltinTypeAliasLike()

function isBuiltinTypeAliasLike(
   program, 
   type, 
   predicate): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`
`predicate`	(`subType`) => `boolean`

Returns

boolean

Defined in

builtinSymbolLikes.ts:88

isErrorLike()

function isErrorLike(program, type): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`

Returns

boolean

Example

class Foo extends Error {}
new Foo()
//   ^ ErrorLike

Defined in

builtinSymbolLikes.ts:41

isNullableType()

function isNullableType(type): boolean

Checks if the given type is (or accepts) nullable

Parameters

Parameter	Type
`type`	`Type`

Returns

boolean

Defined in

predicates.ts:12

isPromiseConstructorLike()

function isPromiseConstructorLike(program, type): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`

Returns

boolean

Example

const value = Promise
value.reject
// ^ PromiseConstructorLike

Defined in

builtinSymbolLikes.ts:26

isPromiseLike()

function isPromiseLike(program, type): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`

Returns

boolean

Example

class DerivedClass extends Promise<number> {}
DerivedClass.reject
// ^ PromiseLike

Defined in

builtinSymbolLikes.ts:14

isReadonlyErrorLike()

function isReadonlyErrorLike(program, type): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`

Returns

boolean

Example

type T = Readonly<Error>
//   ^ ReadonlyErrorLike

Defined in

builtinSymbolLikes.ts:52

isReadonlyTypeLike()

function isReadonlyTypeLike(
   program, 
   type, 
   predicate?): boolean

Parameters

Parameter	Type
`program`	`Program`
`type`	`Type`
`predicate`?	(`subType`) => `boolean`

Returns

boolean

Example

type T = Readonly<{ foo: 'bar' }>
//   ^ ReadonlyTypeLike

Defined in

builtinSymbolLikes.ts:72

isSymbolFromDefaultLibrary()

function isSymbolFromDefaultLibrary(program, symbol): boolean

Parameters

Parameter	Type
`program`	`Program`
`symbol`	`undefined` \| `Symbol`

Returns

boolean

Defined in

isSymbolFromDefaultLibrary.ts:3

isTypeAnyArrayType()

function isTypeAnyArrayType(type, checker): boolean

Parameters

Parameter	Type
`type`	`Type`
`checker`	`TypeChecker`

Returns

boolean

true if the type is any[]

Defined in

predicates.ts:88

isTypeAnyType()

function isTypeAnyType(type): boolean

Parameters

Parameter	Type
`type`	`Type`

Returns

boolean

true if the type is any

Defined in

predicates.ts:75

isTypeArrayTypeOrUnionOfArrayTypes()

function isTypeArrayTypeOrUnionOfArrayTypes(type, checker): boolean

Checks if the given type is either an array type, or a union made up solely of array types.

Parameters

Parameter	Type
`type`	`Type`
`checker`	`TypeChecker`

Returns

boolean

Defined in

predicates.ts:27

isTypeBigIntLiteralType()

function isTypeBigIntLiteralType(type): type is BigIntLiteralType

Parameters

Parameter	Type
`type`	`Type`

Returns

type is BigIntLiteralType

Defined in

predicates.ts:182

isTypeFlagSet()

function isTypeFlagSet(
   type, 
   flagsToCheck, 
   isReceiver?): boolean

Parameters

Parameter	Type	Description
`type`	`Type`	-
`flagsToCheck`	`TypeFlags`	The composition of one or more `ts.TypeFlags`.
`isReceiver`?	`boolean`	Whether the type is a receiving type (e.g. the type of a called function's parameter).

Returns

boolean

Remarks

Note that if the type is a union, this function will decompose it into the parts and get the flags of every union constituent. If this is not desired, use the isTypeFlag function from tsutils.

Defined in

typeFlagUtils.ts:27

isTypeNeverType()

function isTypeNeverType(type): boolean

Parameters

Parameter	Type
`type`	`Type`

Returns

boolean

true if the type is never

Defined in

predicates.ts:43

isTypeReadonly()

function isTypeReadonly(
   program, 
   type, 
   options): boolean

Checks if the given type is readonly

Parameters

Parameter	Type	Default value
`program`	`Program`	`undefined`
`type`	`Type`	`undefined`
`options`	`ReadonlynessOptions`	`readonlynessOptionsDefaults`

Returns

boolean

Defined in

isTypeReadonly.ts:334

isTypeReferenceType()

function isTypeReferenceType(type): type is TypeReference

Parameters

Parameter	Type
`type`	`Type`

Returns

type is TypeReference

Defined in

predicates.ts:64

isTypeTemplateLiteralType()

function isTypeTemplateLiteralType(type): type is TemplateLiteralType

Parameters

Parameter	Type
`type`	`Type`

Returns

type is TemplateLiteralType

Defined in

predicates.ts:188

isTypeUnknownArrayType()

function isTypeUnknownArrayType(type, checker): boolean

Parameters

Parameter	Type
`type`	`Type`
`checker`	`TypeChecker`

Returns

boolean

true if the type is unknown[]

Defined in

predicates.ts:101

isTypeUnknownType()

function isTypeUnknownType(type): boolean

Parameters

Parameter	Type
`type`	`Type`

Returns

boolean

true if the type is unknown

Defined in

predicates.ts:50

isUnsafeAssignment()

function isUnsafeAssignment(
   type, 
   receiver, 
   checker, 
   senderNode): {
  receiver: ts.Type;
  sender: ts.Type;
 } | false

Does a simple check to see if there is an any being assigned to a non-any type.

This also checks generic positions to ensure there's no unsafe sub-assignments. Note: in the case of generic positions, it makes the assumption that the two types are the same.

Parameters

Parameter	Type
`type`	`Type`
`receiver`	`Type`
`checker`	`TypeChecker`
`senderNode`	`null` \| `Node`

Returns

{ receiver: ts.Type; sender: ts.Type; } | false

false if it's safe, or an object with the two types if it's unsafe

Example

See tests for examples

Defined in

isUnsafeAssignment.ts:19

requiresQuoting()

function requiresQuoting(name, target): boolean

Indicates whether identifiers require the use of quotation marks when accessing property definitions and dot notation.

Parameters

Parameter	Type	Default value
`name`	`string`	`undefined`
`target`	`ScriptTarget`	`ts.ScriptTarget.ESNext`

Returns

boolean

Defined in

requiresQuoting.ts:3

typeIsOrHasBaseType()

function typeIsOrHasBaseType(type, parentType): boolean

Parameters

Parameter	Type
`type`	`Type`
`parentType`	`Type`

Returns

boolean

Whether a type is an instance of the parent type, including for the parent's base types.

Defined in

predicates.ts:156

typeMatchesSomeSpecifier()

function typeMatchesSomeSpecifier(
   type, 
   specifiers, 
   program): boolean

Parameters

Parameter	Type	Default value
`type`	`Type`	`undefined`
`specifiers`	`TypeOrValueSpecifier`[]	`[]`
`program`	`Program`	`undefined`

Returns

boolean

Defined in

TypeOrValueSpecifier.ts:199

typeMatchesSpecifier()

function typeMatchesSpecifier(
   type, 
   specifier, 
   program): boolean

Parameters

Parameter	Type
`type`	`Type`
`specifier`	`TypeOrValueSpecifier`
`program`	`Program`

Returns

boolean

Defined in

TypeOrValueSpecifier.ts:165

Variables

readonlynessOptionsDefaults

const readonlynessOptionsDefaults: ReadonlynessOptions;

Defined in

isTypeReadonly.ts:40

readonlynessOptionsSchema

const readonlynessOptionsSchema: object;

Type declaration

Name	Type	Default value	Defined in
`additionalProperties`	`false`	false	isTypeReadonly.ts:30
`properties`	`object`	-	isTypeReadonly.ts:31
`properties.allow`	`object`	typeOrValueSpecifiersSchema	isTypeReadonly.ts:32
`properties.allow.items`	`object`	-	TypeOrValueSpecifier.ts:71
`properties.allow.items.oneOf`	[`object`, `object`, `object`, `object`]	-	TypeOrValueSpecifier.ts:72
`properties.allow.type`	`"array"`	'array'	TypeOrValueSpecifier.ts:162
`properties.treatMethodsAsReadonly`	`object`	-	isTypeReadonly.ts:33
`properties.treatMethodsAsReadonly.type`	`"boolean"`	'boolean'	isTypeReadonly.ts:34
`type`	`"object"`	'object'	isTypeReadonly.ts:37

Defined in

isTypeReadonly.ts:29

typeOrValueSpecifiersSchema

const typeOrValueSpecifiersSchema: object;

Type declaration

Name	Type	Default value	Defined in
`items`	`object`	-	TypeOrValueSpecifier.ts:71
`items.oneOf`	[`object`, `object`, `object`, `object`]	-	TypeOrValueSpecifier.ts:72
`type`	`"array"`	'array'	TypeOrValueSpecifier.ts:162

Defined in

TypeOrValueSpecifier.ts:70

Enumerations

AnyType

Enumeration Members

Enumeration Member	Value	Defined in
`Any`	`0`	predicates.ts:112
`AnyArray`	`2`	predicates.ts:114
`PromiseAny`	`1`	predicates.ts:113
`Safe`	`3`	predicates.ts:115

Interfaces

FileSpecifier

Describes specific types or values declared in local files. See TypeOrValueSpecifier > FileSpecifier.

Properties

Property	Type	Description	Defined in
`from`	`"file"`	-	TypeOrValueSpecifier.ts:16
`name`	`string` \| `string`[]	Type or value name(s) to match on.	TypeOrValueSpecifier.ts:21
`path?`	`string`	A specific file the types or values must be declared in.	TypeOrValueSpecifier.ts:26

LibSpecifier

Describes specific types or values declared in TypeScript's built-in lib definitions. See TypeOrValueSpecifier > LibSpecifier.

Properties

Property	Type	Description	Defined in
`from`	`"lib"`	-	TypeOrValueSpecifier.ts:34
`name`	`string` \| `string`[]	Type or value name(s) to match on.	TypeOrValueSpecifier.ts:39

PackageSpecifier

Describes specific types or values imported from packages. See TypeOrValueSpecifier > PackageSpecifier.

Properties

Property	Type	Description	Defined in
`from`	`"package"`	-	TypeOrValueSpecifier.ts:47
`name`	`string` \| `string`[]	Type or value name(s) to match on.	TypeOrValueSpecifier.ts:52
`package`	`string`	Package name the type or value must be declared in.	TypeOrValueSpecifier.ts:57

ReadonlynessOptions

Properties

Property	Modifier	Type	Defined in
`allow?`	`readonly`	`TypeOrValueSpecifier`[]	isTypeReadonly.ts:25
`treatMethodsAsReadonly?`	`readonly`	`boolean`	isTypeReadonly.ts:26

Type Aliases

TypeOrValueSpecifier

type TypeOrValueSpecifier: string | FileSpecifier | LibSpecifier | PackageSpecifier;

A centralized format for rule options to describe specific types and/or values. See TypeOrValueSpecifier.

Defined in

TypeOrValueSpecifier.ts:64

Functions​

containsAllTypesByName()​

Parameters​

Returns​

Defined in​

discriminateAnyType()​

Parameters​

Returns​

Defined in​

getConstrainedTypeAtLocation()​

Parameters​

Returns​

Defined in​

getContextualType()​

Parameters​

Returns​

Defined in​

getDeclaration()​

Parameters​

Returns​

Defined in​

getSourceFileOfNode()​

Parameters​

Returns​

Defined in​

getTypeFlags()​

Parameters​

Returns​

Defined in​

getTypeName()​

Parameters​

Returns​

Defined in​

getTypeOfPropertyOfName()​

Parameters​

Returns​

Defined in​

getTypeOfPropertyOfType()​

Parameters​

Returns​

Defined in​

isBuiltinSymbolLike()​

Parameters​

Returns​

Defined in​

isBuiltinSymbolLikeRecurser()​

Parameters​

Returns​

Defined in​

isBuiltinTypeAliasLike()​

Parameters​

Returns​

Defined in​

isErrorLike()​

Parameters​

Returns​

Example​

Defined in​

isNullableType()​

Parameters​

Returns​

Defined in​

isPromiseConstructorLike()​

Parameters​

Returns​

Example​

Defined in​

isPromiseLike()​

Parameters​

Returns​

Example​

Defined in​

isReadonlyErrorLike()​

Parameters​

Returns​

Example​

Defined in​

isReadonlyTypeLike()​

Parameters​

Returns​

Functions

containsAllTypesByName()

Parameters

Returns

Defined in

discriminateAnyType()

Parameters

Returns

Defined in

getConstrainedTypeAtLocation()

Parameters

Returns

Defined in

getContextualType()

Parameters

Returns

Defined in

getDeclaration()

Parameters

Returns

Defined in

getSourceFileOfNode()

Parameters

Returns

Defined in

getTypeFlags()

Parameters

Returns

Defined in

getTypeName()

Parameters

Returns

Defined in

getTypeOfPropertyOfName()

Parameters

Returns

Defined in

getTypeOfPropertyOfType()

Parameters

Returns

Defined in

isBuiltinSymbolLike()

Parameters

Returns

Defined in

isBuiltinSymbolLikeRecurser()

Parameters

Returns

Defined in

isBuiltinTypeAliasLike()

Parameters

Returns

Defined in

isErrorLike()

Parameters

Returns

Example

Defined in

isNullableType()

Parameters

Returns

Defined in

isPromiseConstructorLike()

Parameters

Returns

Example

Defined in

isPromiseLike()

Parameters

Returns

Example

Defined in

isReadonlyErrorLike()

Parameters

Returns

Example

Defined in

isReadonlyTypeLike()

Parameters

Returns