@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;

Defined in: containsAllTypesByName.ts:13

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).

---

discriminateAnyType()

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

Defined in: discriminateAnyType.ts:17

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.

---

getConstrainedTypeAtLocation()

function getConstrainedTypeAtLocation(services, node): Type;

Defined in: getConstrainedTypeAtLocation.ts:16

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

Warning - if the type is generic and does not have a constraint, the type will be returned as-is, rather than returning an unknown type. This can be checked for by checking for the type flag ts.TypeFlags.TypeParameter.

Parameters

Parameter	Type
services	ParserServicesWithTypeInformation
node	Node

Returns

Type

See

https://github.com/typescript-eslint/typescript-eslint/issues/10438

---

getContextualType()

function getContextualType(checker, node): undefined | Type;

Defined in: getContextualType.ts:8

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

undefined | Type

---

getDeclaration()

function getDeclaration(services, node): null | Declaration;

Defined in: getDeclaration.ts:10

Gets the declaration for the given variable

Parameters

Parameter	Type
services	ParserServicesWithTypeInformation
node	Node

Returns

null | Declaration

---

getSourceFileOfNode()

function getSourceFileOfNode(node): SourceFile;

Defined in: getSourceFileOfNode.ts:6

Gets the source file for a given node

Parameters

Parameter	Type
node	Node

Returns

SourceFile

---

getTypeFlags()

function getTypeFlags(type): TypeFlags;

Defined in: typeFlagUtils.ts:9

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

Parameters

Parameter	Type
type	Type

Returns

TypeFlags

---

getTypeName()

function getTypeName(typeChecker, type): string;

Defined in: getTypeName.ts:8

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

---

getTypeOfPropertyOfName()

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

Defined in: propertyTypes.ts:3

Parameters

Parameter	Type
checker	TypeChecker
type	Type
name	string
escapedName?	__String

Returns

undefined | Type

---

getTypeOfPropertyOfType()

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

Defined in: propertyTypes.ts:25

Parameters

Parameter	Type
checker	TypeChecker
type	Type
property	Symbol

Returns

undefined | Type

---

isBuiltinSymbolLike()

function isBuiltinSymbolLike(
   program, 
   type, 
   symbolName): boolean;

Defined in: builtinSymbolLikes.ts:121

Parameters

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

Returns

boolean

---

isBuiltinSymbolLikeRecurser()

function isBuiltinSymbolLikeRecurser(
   program, 
   type, 
   predicate): boolean;

Defined in: builtinSymbolLikes.ts:147

Parameters

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

Returns

boolean

---

isBuiltinTypeAliasLike()

function isBuiltinTypeAliasLike(
   program, 
   type, 
   predicate): boolean;

Defined in: builtinSymbolLikes.ts:88

Parameters

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

Returns

boolean

---

isErrorLike()

function isErrorLike(program, type): boolean;

Defined in: builtinSymbolLikes.ts:41

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

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

---

isNullableType()

function isNullableType(type): boolean;

Defined in: predicates.ts:12

Checks if the given type is (or accepts) nullable

Parameters

Parameter	Type
type	Type

Returns

boolean

---

isPromiseConstructorLike()

function isPromiseConstructorLike(program, type): boolean;

Defined in: builtinSymbolLikes.ts:26

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

const value = Promise
value.reject
// ^ PromiseConstructorLike

---

isPromiseLike()

function isPromiseLike(program, type): boolean;

Defined in: builtinSymbolLikes.ts:14

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

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

---

isReadonlyErrorLike()

function isReadonlyErrorLike(program, type): boolean;

Defined in: builtinSymbolLikes.ts:52

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

type T = Readonly<Error>
//   ^ ReadonlyErrorLike

---

isReadonlyTypeLike()

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

Defined in: builtinSymbolLikes.ts:72

Parameters

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

Returns

boolean

Example

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

---

isSymbolFromDefaultLibrary()

function isSymbolFromDefaultLibrary(program, symbol): boolean;

Defined in: isSymbolFromDefaultLibrary.ts:3

Parameters

Parameter	Type
program	Program
symbol	undefined | Symbol

Returns

boolean

---

isTypeAnyArrayType()

function isTypeAnyArrayType(type, checker): boolean;

Defined in: predicates.ts:88

Parameters

Parameter	Type
type	Type
checker	TypeChecker

Returns

boolean

true if the type is any[]

---

isTypeAnyType()

function isTypeAnyType(type): boolean;

Defined in: predicates.ts:75

Parameters

Parameter	Type
type	Type

Returns

boolean

true if the type is any

---

isTypeArrayTypeOrUnionOfArrayTypes()

function isTypeArrayTypeOrUnionOfArrayTypes(type, checker): boolean;

Defined in: predicates.ts:27

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

---

isTypeBigIntLiteralType()

function isTypeBigIntLiteralType(type): type is BigIntLiteralType;

Defined in: predicates.ts:140

Parameters

Parameter	Type
type	Type

Returns

type is BigIntLiteralType

---

isTypeFlagSet()

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

Defined in: typeFlagUtils.ts:27

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.

---

isTypeNeverType()

function isTypeNeverType(type): boolean;

Defined in: predicates.ts:43

Parameters

Parameter	Type
type	Type

Returns

boolean

true if the type is never

---

isTypeReadonly()

function isTypeReadonly(
   program, 
   type, 
   options): boolean;

Defined in: isTypeReadonly.ts:334

Checks if the given type is readonly

Parameters

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

Returns

boolean

---

isTypeReferenceType()

function isTypeReferenceType(type): type is TypeReference;

Defined in: predicates.ts:64

Parameters

Parameter	Type
type	Type

Returns

type is TypeReference

---

isTypeTemplateLiteralType()

function isTypeTemplateLiteralType(type): type is TemplateLiteralType;

Defined in: predicates.ts:146

Parameters

Parameter	Type
type	Type

Returns

type is TemplateLiteralType

---

isTypeUnknownArrayType()

function isTypeUnknownArrayType(type, checker): boolean;

Defined in: predicates.ts:101

Parameters

Parameter	Type
type	Type
checker	TypeChecker

Returns

boolean

true if the type is unknown[]

---

isTypeUnknownType()

function isTypeUnknownType(type): boolean;

Defined in: predicates.ts:50

Parameters

Parameter	Type
type	Type

Returns

boolean

true if the type is unknown

---

isUnsafeAssignment()

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

Defined in: isUnsafeAssignment.ts:19

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

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

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

Example

See tests for examples

---

requiresQuoting()

function requiresQuoting(name, target): boolean;

Defined in: requiresQuoting.ts:3

• 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

---

typeIsOrHasBaseType()

function typeIsOrHasBaseType(type, parentType): boolean;

Defined in: predicates.ts:114

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.

---

typeMatchesSomeSpecifier()

function typeMatchesSomeSpecifier(
   type, 
   specifiers, 
   program): boolean;

Defined in: TypeOrValueSpecifier.ts:216

Parameters

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

Returns

boolean

---

typeMatchesSpecifier()

function typeMatchesSpecifier(
   type, 
   specifier, 
   program): boolean;

Defined in: TypeOrValueSpecifier.ts:165

Parameters

Parameter	Type
type	Type
specifier	TypeOrValueSpecifier
program	Program

Returns

boolean

Variables

readonlynessOptionsDefaults

const readonlynessOptionsDefaults: ReadonlynessOptions;

Defined in: isTypeReadonly.ts:40

---

readonlynessOptionsSchema

const readonlynessOptionsSchema: object;

Defined in: isTypeReadonly.ts:29

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	[{ type: "string"; }, { additionalProperties: false; properties: { from: { enum: ["file"]; type: "string"; }; name: { oneOf: [{ type: "string"; }, { items: { type: ...; }; minItems: 1; type: "array"; uniqueItems: true; }]; }; path: { type: "string"; }; }; required: ["from", "name"]; type: "object"; }, { additionalProperties: false; properties: { from: { enum: ["lib"]; type: "string"; }; name: { oneOf: [{ type: "string"; }, { items: { type: ...; }; minItems: 1; type: "array"; uniqueItems: true; }]; }; }; required: ["from", "name"]; type: "object"; }, { additionalProperties: false; properties: { from: { enum: ["package"]; type: "string"; }; name: { oneOf: [{ type: "string"; }, { items: { type: ...; }; minItems: 1; type: "array"; uniqueItems: true; }]; }; package: { type: "string"; }; }; required: ["from", "name", "package"]; type: "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

---

typeOrValueSpecifiersSchema

const typeOrValueSpecifiersSchema: object;

Defined in: TypeOrValueSpecifier.ts:70

Type declaration

Name	Type	Default value	Defined in
items	object	-	TypeOrValueSpecifier.ts:71
items.oneOf	[{ type: "string"; }, { additionalProperties: false; properties: { from: { enum: ["file"]; type: "string"; }; name: { oneOf: [{ type: "string"; }, { items: { type: "string"; }; minItems: 1; type: "array"; uniqueItems: true; }]; }; path: { type: "string"; }; }; required: ["from", "name"]; type: "object"; }, { additionalProperties: false; properties: { from: { enum: ["lib"]; type: "string"; }; name: { oneOf: [{ type: "string"; }, { items: { type: "string"; }; minItems: 1; type: "array"; uniqueItems: true; }]; }; }; required: ["from", "name"]; type: "object"; }, { additionalProperties: false; properties: { from: { enum: ["package"]; type: "string"; }; name: { oneOf: [{ type: "string"; }, { items: { type: "string"; }; minItems: 1; type: "array"; uniqueItems: true; }]; }; package: { type: "string"; }; }; required: ["from", "name", "package"]; type: "object"; }]	-	TypeOrValueSpecifier.ts:72
type	"array"	'array'	TypeOrValueSpecifier.ts:162

Enumerations

AnyType

Defined in: discriminateAnyType.ts:7

Enumeration Members

Enumeration Member	Value	Defined in
Any	0	discriminateAnyType.ts:8
AnyArray	2	discriminateAnyType.ts:10
PromiseAny	1	discriminateAnyType.ts:9
Safe	3	discriminateAnyType.ts:11

Interfaces

FileSpecifier

Defined in: TypeOrValueSpecifier.ts:15

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

Defined in: TypeOrValueSpecifier.ts:33

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

Defined in: TypeOrValueSpecifier.ts:46

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

Defined in: isTypeReadonly.ts:24

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;

Defined in: TypeOrValueSpecifier.ts:64

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