1 | import type {IsNever} from './is-never';
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2 | import type {UnionToIntersection} from './union-to-intersection';
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3 |
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4 | /**
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5 | Returns the last element of a union type.
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6 |
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7 | @example
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8 | ```
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9 | type Last = LastOfUnion<1 | 2 | 3>;
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10 | //=> 3
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11 | ```
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12 | */
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13 | type LastOfUnion<T> =
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14 | UnionToIntersection<T extends any ? () => T : never> extends () => (infer R)
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15 | ? R
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16 | : never;
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17 |
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18 | /**
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19 | Convert a union type into an unordered tuple type of its elements.
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20 |
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21 | This can be useful when you have objects with a finite set of keys and want a type defining only the allowed keys, but do not want to repeat yourself.
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22 |
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23 | @example
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24 | ```
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25 | import type {UnionToTuple} from 'type-fest';
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26 |
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27 | type Numbers = 1 | 2 | 3;
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28 | type NumbersTuple = UnionToTuple<Numbers>;
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29 | //=> [1, 2, 3]
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30 | ```
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31 |
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32 | @example
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33 | ```
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34 | import type {UnionToTuple} from 'type-fest';
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35 |
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36 | const pets = {
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37 | dog: '🐶',
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38 | cat: '🐱',
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39 | snake: '🐍',
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40 | };
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41 |
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42 | type Pet = keyof typeof pets;
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43 | //=> 'dog' | 'cat' | 'snake'
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44 |
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45 | const petList = Object.keys(pets) as UnionToTuple<Pet>;
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46 | //=> ['dog', 'cat', 'snake']
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47 | ```
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48 |
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49 | @category Array
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50 | */
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51 | export type UnionToTuple<T, L = LastOfUnion<T>> =
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52 | IsNever<T> extends false
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53 | ? [...UnionToTuple<Exclude<T, L>>, L]
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54 | : [];
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