Use import type

Closes #390

Author: sindresorhus

package.json

@@ -33,9 +33,9 @@
 	],
 	"devDependencies": {
 		"@sindresorhus/tsconfig": "~0.7.0",
-		"expect-type": "^0.12.0",
-		"tsd": "^0.17.0",
-		"typescript": ">=4.2",
+		"expect-type": "^0.13.0",
+		"tsd": "^0.20.0",
+		"typescript": "^4.6.3",
 		"xo": "^0.43.0"
 	},
 	"types": "./index.d.ts",

readme.md

@@ -67,7 +67,7 @@ npm install type-fest
 ## Usage
 
 ```ts
-import {Except} from 'type-fest';
+import type {Except} from 'type-fest';
 
 type Foo = {
 	unicorn: string;

source/async-return-type.d.ts

@@ -1,4 +1,4 @@
-import {PromiseValue} from './promise-value';
+import type {PromiseValue} from './promise-value';
 
 type AsyncFunction = (...args: any[]) => Promise<unknown>;
 
@@ -9,7 +9,7 @@ There has been [discussion](https://github.com/microsoft/TypeScript/pull/35998)
 
 @example
 ```ts
-import {AsyncReturnType} from 'type-fest';
+import type {AsyncReturnType} from 'type-fest';
 import {asyncFunction} from 'api';
 
 // This type resolves to the unwrapped return type of `asyncFunction`.

source/asyncify.d.ts

@@ -1,5 +1,5 @@
-import {PromiseValue} from './promise-value';
-import {SetReturnType} from './set-return-type';
+import type {PromiseValue} from './promise-value';
+import type {SetReturnType} from './set-return-type';
 
 /**
 Create an async version of the given function type, by boxing the return type in `Promise` while keeping the same parameter types.
@@ -8,7 +8,7 @@ Use-case: You have two functions, one synchronous and one asynchronous that do t
 
 @example
 ```
-import {Asyncify} from 'type-fest';
+import type {Asyncify} from 'type-fest';
 
 // Synchronous function.
 function getFooSync(someArg: SomeType): Foo {

source/camel-case.d.ts

@@ -1,5 +1,5 @@
-import {WordSeparators} from '../source/utilities';
-import {Split} from './split';
+import type {WordSeparators} from '../source/utilities';
+import type {Split} from './split';
 
 /**
 Step by step takes the first item in an array literal, formats it and adds it to a string literal, and then recursively appends the remainder.
@@ -36,7 +36,7 @@ This can be useful when, for example, converting some kebab-cased command-line f
 
 @example
 ```
-import {CamelCase} from 'type-fest';
+import type {CamelCase} from 'type-fest';
 
 // Simple
 

source/camel-cased-properties-deep.d.ts

@@ -1,4 +1,4 @@
-import {CamelCase} from './camel-case';
+import type {CamelCase} from './camel-case';
 
 /**
 Convert object properties to camel case recursively.
@@ -10,6 +10,8 @@ This can be useful when, for example, converting some API types from a different
 
 @example
 ```
+import type {CamelCasedPropertiesDeep} from 'type-fest';
+
 interface User {
 	UserId: number;
 	UserName: string;

source/camel-cased-properties.d.ts

@@ -1,4 +1,4 @@
-import {CamelCase} from './camel-case';
+import type {CamelCase} from './camel-case';
 
 /**
 Convert object properties to camel case but not recursively.
@@ -10,6 +10,8 @@ This can be useful when, for example, converting some API types from a different
 
 @example
 ```
+import type {CamelCasedProperties} from 'type-fest';
+
 interface User {
 	UserId: number;
 	UserName: string;

source/conditional-except.d.ts

@@ -1,5 +1,5 @@
-import {Except} from './except';
-import {ConditionalKeys} from './conditional-keys';
+import type {Except} from './except';
+import type {ConditionalKeys} from './conditional-keys';
 
 /**
 Exclude keys from a shape that matches the given `Condition`.
@@ -8,7 +8,7 @@ This is useful when you want to create a new type with a specific set of keys fr
 
 @example
 ```
-import {Primitive, ConditionalExcept} from 'type-fest';
+import type {Primitive, ConditionalExcept} from 'type-fest';
 
 class Awesome {
 	name: string;
@@ -24,7 +24,7 @@ type ExceptPrimitivesFromAwesome = ConditionalExcept<Awesome, Primitive>;
 
 @example
 ```
-import {ConditionalExcept} from 'type-fest';
+import type {ConditionalExcept} from 'type-fest';
 
 interface Example {
 	a: string;

source/conditional-keys.d.ts

@@ -5,7 +5,7 @@ Internally this is used for the `ConditionalPick` and `ConditionalExcept` types.
 
 @example
 ```
-import {ConditionalKeys} from 'type-fest';
+import type {ConditionalKeys} from 'type-fest';
 
 interface Example {
 	a: string;
@@ -22,6 +22,8 @@ To support partial types, make sure your `Condition` is a union of undefined (fo
 
 @example
 ```
+import type {ConditionalKeys} from 'type-fest';
+
 type StringKeysAndUndefined = ConditionalKeys<Example, string | undefined>;
 //=> 'a' | 'c'
 ```

source/conditional-pick.d.ts

@@ -1,4 +1,4 @@
-import {ConditionalKeys} from './conditional-keys';
+import type {ConditionalKeys} from './conditional-keys';
 
 /**
 Pick keys from the shape that matches the given `Condition`.
@@ -7,7 +7,7 @@ This is useful when you want to create a new type from a specific subset of an e
 
 @example
 ```
-import {Primitive, ConditionalPick} from 'type-fest';
+import type {Primitive, ConditionalPick} from 'type-fest';
 
 class Awesome {
 	name: string;
@@ -23,7 +23,7 @@ type PickPrimitivesFromAwesome = ConditionalPick<Awesome, Primitive>;
 
 @example
 ```
-import {ConditionalPick} from 'type-fest';
+import type {ConditionalPick} from 'type-fest';
 
 interface Example {
 	a: string;

source/delimiter-case.d.ts

@@ -1,4 +1,4 @@
-import {UpperCaseCharacters, WordSeparators} from '../source/utilities';
+import type {UpperCaseCharacters, WordSeparators} from '../source/utilities';
 
 /**
 Unlike a simpler split, this one includes the delimiter splitted on in the resulting array literal. This is to enable splitting on, for example, upper-case characters.
@@ -54,7 +54,7 @@ This can be useful when, for example, converting a camel-cased object property t
 
 @example
 ```
-import {DelimiterCase} from 'type-fest';
+import type {DelimiterCase} from 'type-fest';
 
 // Simple
 

source/delimiter-cased-properties-deep.d.ts

@@ -1,4 +1,4 @@
-import {DelimiterCase} from './delimiter-case';
+import type {DelimiterCase} from './delimiter-case';
 
 /**
 Convert object properties to delimiter case recursively.
@@ -10,6 +10,8 @@ This can be useful when, for example, converting some API types from a different
 
 @example
 ```
+import type {DelimiterCasedPropertiesDeep} from 'type-fest';
+
 interface User {
 	userId: number;
 	userName: string;

source/delimiter-cased-properties.d.ts

@@ -1,4 +1,4 @@
-import {DelimiterCase} from './delimiter-case';
+import type {DelimiterCase} from './delimiter-case';
 
 /**
 Convert object properties to delimiter case but not recursively.
@@ -10,6 +10,8 @@ This can be useful when, for example, converting some API types from a different
 
 @example
 ```
+import type {DelimiterCasedProperties} from 'type-fest';
+
 interface User {
 	userId: number;
 	userName: string;

source/entries.d.ts

@@ -1,4 +1,4 @@
-import {ArrayEntry, MapEntry, ObjectEntry, SetEntry} from './entry';
+import type {ArrayEntry, MapEntry, ObjectEntry, SetEntry} from './entry';
 
 type ArrayEntries<BaseType extends readonly unknown[]> = Array<ArrayEntry<BaseType>>;
 type MapEntries<BaseType> = Array<MapEntry<BaseType>>;
@@ -14,7 +14,7 @@ For example the {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/R
 
 @example
 ```
-import {Entries} from 'type-fest';
+import type {Entries} from 'type-fest';
 
 interface Example {
 	someKey: number;

source/entry.d.ts

@@ -15,7 +15,7 @@ For example the {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/R
 
 @example
 ```
-import {Entry} from 'type-fest';
+import type {Entry} from 'type-fest';
 
 interface Example {
 	someKey: number;

source/except.d.ts

@@ -1,4 +1,4 @@
-import {IsEqual} from './internal';
+import type {IsEqual} from './internal';
 
 /**
 Filter out keys from an object.
@@ -38,7 +38,7 @@ This type was proposed to the TypeScript team, which declined it, saying they pr
 
 @example
 ```
-import {Except} from 'type-fest';
+import type {Except} from 'type-fest';
 
 type Foo = {
 	a: number;

source/fixed-length-array.d.ts

@@ -15,7 +15,7 @@ Use-cases:
 
 @example
 ```
-import {FixedLengthArray} from 'type-fest';
+import type {FixedLengthArray} from 'type-fest';
 
 type FencingTeam = FixedLengthArray<string, 3>;
 

source/get.d.ts

@@ -1,6 +1,6 @@
-import {StringDigit} from '../source/utilities';
-import {Split} from './split';
-import {StringKeyOf} from './string-key-of';
+import type {StringDigit} from '../source/utilities';
+import type {Split} from './split';
+import type {StringKeyOf} from './string-key-of';
 
 type GetOptions = {
 	strict?: boolean;
@@ -141,7 +141,7 @@ Use-case: Retrieve a property from deep inside an API response or some other com
 
 @example
 ```
-import {Get} from 'type-fest';
+import type {Get} from 'type-fest';
 import * as lodash from 'lodash';
 
 const get = <BaseType, Path extends string | readonly string[]>(object: BaseType, path: Path): Get<BaseType, Path> =>

source/includes.d.ts

@@ -1,4 +1,4 @@
-import {IsEqual} from './internal';
+import type {IsEqual} from './internal';
 
 /**
 Returns a boolean for whether the given array includes the given item.
@@ -7,7 +7,7 @@ This can be useful if another type wants to make a decision based on whether the
 
 @example
 ```
-import {Includes} from 'type-fest';
+import type {Includes} from 'type-fest';
 
 type hasRed<array extends any[]> = Includes<array, 'red'>;
 ```

source/internal.d.ts

@@ -1,4 +1,4 @@
-import {Primitive} from './primitive';
+import type {Primitive} from './primitive';
 
 /**
 Returns a boolean for whether the two given types are equal.

source/invariant-of.d.ts

@@ -1,4 +1,4 @@
-import {Opaque} from './opaque';
+import type {Opaque} from './opaque';
 
 /**
 Create an [invariant type](https://basarat.gitbook.io/typescript/type-system/type-compatibility#footnote-invariance), which is a type that does not accept supertypes and subtypes.
@@ -9,6 +9,8 @@ Use-case:
 
 @example
 ```
+import type {InvariantOf} from 'type-fest';
+
 class Animal {
 	constructor(public name: string){}
 }
@@ -32,6 +34,8 @@ invariantAnimalArray = invariantCatArray; // Error: Type 'InvariantOf<Cat>[]' is
 
 @example
 ```
+import type {InvariantOf} from 'type-fest';
+
 // In covariance (default)
 
 interface FooBar {

source/iterable-element.d.ts

@@ -9,6 +9,8 @@ Here is an example of `IterableElement` in action with a generator function:
 
 @example
 ```
+import type {IterableElement} from 'type-fest';
+
 function * iAmGenerator() {
 	yield 1;
 	yield 2;
@@ -21,6 +23,8 @@ And here is an example with an async generator:
 
 @example
 ```
+import type {IterableElement} from 'type-fest';
+
 async function * iAmGeneratorAsync() {
 	yield 'hi';
 	yield true;
@@ -35,6 +39,8 @@ An example with an array of strings:
 
 @example
 ```
+import type {IterableElement} from 'type-fest';
+
 type MeString = IterableElement<string[]>
 ```
 

source/join.d.ts

@@ -5,7 +5,7 @@ Use-case: Defining key paths in a nested object. For example, for dot-notation f
 
 @example
 ```
-import {Join} from 'type-fest';
+import type {Join} from 'type-fest';
 
 // Mixed (strings & numbers) items; result is: 'foo.0.baz'
 const path: Join<['foo', 0, 'baz'], '.'> = ['foo', 0, 'baz'].join('.');

source/jsonify.d.ts

@@ -1,4 +1,4 @@
-import {JsonPrimitive, JsonValue} from './basic';
+import type {JsonPrimitive, JsonValue} from './basic';
 
 // Note: The return value has to be `any` and not `unknown` so it can match `void`.
 type NotJsonable = ((...args: any[]) => any) | undefined;
@@ -23,6 +23,8 @@ An interface cannot be structurally compared to `JsonValue` because an interface
 
 @example
 ```
+import type {Jsonify} from 'type-fest';
+
 interface Geometry {
 	type: 'Point' | 'Polygon';
 	coordinates: [number, number];
@@ -51,6 +53,8 @@ Non-JSON values such as `Date` implement `.toJSON()`, so they can be transformed
 
 @example
 ```
+import type {Jsonify} from 'type-fest';
+
 const time = {
 	timeValue: new Date()
 };