@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).

Source

containsAllTypesByName.ts:13

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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

Source

getConstrainedTypeAtLocation.ts:10

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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

Source

getContextualType.ts:8

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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

Source

getDeclaration.ts:10

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getSourceFileOfNode()

function getSourceFileOfNode(node): ts.SourceFile

Gets the source file for a given node

Parameters

Parameter	Type
node	Node

Returns

ts.SourceFile

Source

getSourceFileOfNode.ts:6

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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

Source

typeFlagUtils.ts:9

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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

Source

getTypeName.ts:8

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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

Source

propertyTypes.ts:3

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getTypeOfPropertyOfType()

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

Parameters

Parameter	Type
checker	TypeChecker
type	Type
property	Symbol

Returns

ts.Type | undefined

Source

propertyTypes.ts:25

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isAnyOrAnyArrayTypeDiscriminated()

function isAnyOrAnyArrayTypeDiscriminated(node, checker): AnyType

Parameters

Parameter	Type
node	Node
checker	TypeChecker

Returns

AnyType

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

Source

predicates.ts:119

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isBuiltinSymbolLike()

function isBuiltinSymbolLike(
   program, 
   type, 
   symbolName): boolean

Parameters

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

Returns

boolean

Source

builtinSymbolLikes.ts:120

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isBuiltinSymbolLikeRecurser()

function isBuiltinSymbolLikeRecurser(
   program, 
   type, 
   predicate): boolean

Parameters

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

Returns

boolean

Source

builtinSymbolLikes.ts:146

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isBuiltinTypeAliasLike()

function isBuiltinTypeAliasLike(
   program, 
   type, 
   predicate): boolean

Parameters

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

Returns

boolean

Source

builtinSymbolLikes.ts:87

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isErrorLike()

function isErrorLike(program, type): boolean

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

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

Source

builtinSymbolLikes.ts:40

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isNullableType()

function isNullableType(type): boolean

Checks if the given type is (or accepts) nullable

Parameters

Parameter	Type
type	Type

Returns

boolean

Source

predicates.ts:12

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isPromiseConstructorLike()

function isPromiseConstructorLike(program, type): boolean

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

const value = Promise
value.reject
// ^ PromiseConstructorLike

Source

builtinSymbolLikes.ts:25

---

isPromiseLike()

function isPromiseLike(program, type): boolean

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

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

Source

builtinSymbolLikes.ts:13

---

isReadonlyErrorLike()

function isReadonlyErrorLike(program, type): boolean

Parameters

Parameter	Type
program	Program
type	Type

Returns

boolean

Example

type T = Readonly<Error>
//   ^ ReadonlyErrorLike

Source

builtinSymbolLikes.ts:51

---

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

Source

builtinSymbolLikes.ts:71

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isSymbolFromDefaultLibrary()

function isSymbolFromDefaultLibrary(program, symbol): boolean

Parameters

Parameter	Type
program	Program
symbol	undefined | Symbol

Returns

boolean

Source

isSymbolFromDefaultLibrary.ts:3

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isTypeAnyArrayType()

function isTypeAnyArrayType(type, checker): boolean

Parameters

Parameter	Type
type	Type
checker	TypeChecker

Returns

boolean

true if the type is any[]

Source

predicates.ts:87

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isTypeAnyType()

function isTypeAnyType(type): boolean

Parameters

Parameter	Type
type	Type

Returns

boolean

true if the type is any

Source

predicates.ts:74

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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

Source

predicates.ts:26

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isTypeBigIntLiteralType()

function isTypeBigIntLiteralType(type): type is BigIntLiteralType

Parameters

Parameter	Type
type	Type

Returns

type is BigIntLiteralType

Source

predicates.ts:162

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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.

Source

typeFlagUtils.ts:27

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isTypeNeverType()

function isTypeNeverType(type): boolean

Parameters

Parameter	Type
type	Type

Returns

boolean

true if the type is never

Source

predicates.ts:42

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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

Source

isTypeReadonly.ts:339

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isTypeReferenceType()

function isTypeReferenceType(type): type is TypeReference

Parameters

Parameter	Type
type	Type

Returns

type is TypeReference

Source

predicates.ts:63

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isTypeTemplateLiteralType()

function isTypeTemplateLiteralType(type): type is TemplateLiteralType

Parameters

Parameter	Type
type	Type

Returns

type is TemplateLiteralType

Source

predicates.ts:168

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isTypeUnknownArrayType()

function isTypeUnknownArrayType(type, checker): boolean

Parameters

Parameter	Type
type	Type
checker	TypeChecker

Returns

boolean

true if the type is unknown[]

Source

predicates.ts:100

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isTypeUnknownType()

function isTypeUnknownType(type): boolean

Parameters

Parameter	Type
type	Type

Returns

boolean

true if the type is unknown

Source

predicates.ts:49

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isUnsafeAssignment()

function isUnsafeAssignment(
   type, 
   receiver, 
   checker, 
   senderNode): false | object

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 | object

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

Example

See tests for examples

Source

isUnsafeAssignment.ts:18

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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

Source

requiresQuoting.ts:3

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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.

Source

predicates.ts:136

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typeMatchesSpecifier()

function typeMatchesSpecifier(
   type, 
   specifier, 
   program): boolean

Parameters

Parameter	Type
type	Type
specifier	TypeOrValueSpecifier
program	Program

Returns

boolean

Source

TypeOrValueSpecifier.ts:125

Variables

readonlynessOptionsDefaults

const readonlynessOptionsDefaults: ReadonlynessOptions;

Source

isTypeReadonly.ts:41

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readonlynessOptionsSchema

const readonlynessOptionsSchema: object;

Type declaration

Member	Type	Value
additionalProperties	false	false
properties	object	...
properties.allow	object	...
properties.allow.items	JSONSchema4	typeOrValueSpecifierSchema
properties.allow.type	"array"	'array'
properties.treatMethodsAsReadonly	object	...
properties.treatMethodsAsReadonly.type	"boolean"	'boolean'
type	"object"	'object'

Source

isTypeReadonly.ts:27

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typeOrValueSpecifierSchema

const typeOrValueSpecifierSchema: JSONSchema4;

Source

TypeOrValueSpecifier.ts:33

Enumerations

AnyType

Enumeration Members

Enumeration Member	Value
Any	0
AnyArray	1
Safe	2

Interfaces

FileSpecifier

Properties

Property	Type
from	"file"
name	string | string[]
path?	string

---

LibSpecifier

Properties

Property	Type
from	"lib"
name	string | string[]

---

PackageSpecifier

Properties

Property	Type
from	"package"
name	string | string[]
package	string

---

ReadonlynessOptions

Properties

Property	Modifier	Type
allow?	readonly	TypeOrValueSpecifier[]
treatMethodsAsReadonly?	readonly	boolean

Type Aliases

TypeOrValueSpecifier

type TypeOrValueSpecifier: FileSpecifier | LibSpecifier | PackageSpecifier | string;

Source

TypeOrValueSpecifier.ts:27