any禁止 絶対に型付けを諦めないための便利なユーティリティ関数 / techstand6

Transcript

1. BOZېࢭ
   ઈରʹܕ෇͚ΛఘΊͳ͍ͨΊͷ
   ศརͳϢʔςΟ ϦςΟؔ਺ /PW
   
   
   
   TUBOEGN
   5&$)
   45"/%
   
   5ZQF4DSJQU
   !PLVOPLFOUBSP

2. ୭ w Ԟ໺
   ݡଠ࿠
   !PLVOPLFOUBSP
   w ΫϨε΢ΣΞגࣜձࣾ
   w 5ZQF4DSJQUྺ
   ೥

3. ܕɺ ͪΌΜͱ෇͚ͯ·͔͢ const res = await fetch('/api/users', {method: 'GET'}); const

   users = await res.json();

4. ͜ΕͰຬ଍ͯ͠ͳ͍ ʁ const res = await fetch('/api/users', {method: 'GET'}); const

   users = await res.json() as User[];

5. anyܕʹas TΛࢦఆ͢Δͷ͸ةݥ wʮanyܕ͸ةݥʯ 
 ʜͱ͍͏࿩୊͸ཧղ͍ͯͯ͠΋ɺ as TͳΒฏؾͰ࢖ͬͯ͠· ͏ݱ৔͸গͳ͘ͳ͍
   w Ͱ΋

   ʮany as T΋ةݥʯ
   w anyܕͷ஋ʹas T ʢas User[]ͳͲʣ Λ෇͚ͯ΋ίϯύΠϧΤϥʔʹͳΒͳ͍

6. ͳʹ͕ةݥͳͷ͔ w ͍͘ ΒͰ΋ӕ͕͚ͭΔ
   w ίϯύΠϧ͸௨͍ͬͯͯ΋ɺ ࣮ࡍʹͦ͜ʹྲྀΕͯ͘ Δ஋ͷߏ଄͸ҟͳΔঢ়گ
   w as

   T͸ ʮίϯύΠ ϥΛ͍͍ٗͯΔ͚ͩʯ Ͱ͋Δ

7. ͜ͷίʔ υ͸ΤϥʔʹͳΒͳ͍ const res1 = await fetch('/api/users', {method: 'GET'}); const

   users = await res1.json() as User[]; const res2 = await fetch('/api/items', {method: 'GET'}); const items = await res2.json() as User[]; as Item[] Ͱ͸ʁʁ

8. asΛ࢖Θͣ҆શʹܕ෇͚Λ͢Δ w anyېࢭ
   
   asېࢭ
   w 5ZQF
   QSFEJDBUFTΛ࢖͏ 

   IUUQTXXXUZQFTDSJQUMBOHPSHEPDTIBOECPPLOBSSPXJOHIUNMVTJOHUZQFQSFEJDBUFT
   w

   function isSomething(v: unknown): v is Something { ... 
 Έ͍ͨͳ΍ͭ
   w JG৚݅ࣜʹͯisSomething(v)Λ࢖ͬͨΒɺ 
 ͦͷJGϒϩοΫ಺Ͱ͸v͕Somethingܕͱͯ͠ѻ͑Δ

9. type User = { id: number; name: string; }; function

   hasId(v: unknown): v is { id: unknown } { if (typeof v !== "object" || v === null) { return false; } return "id" in v; } function hasName(v: unknown): v is { name: unknown } { if (typeof v !== "object" || v === null) { return false; } return "name" in v; } function isUser(v: unknown): v is User { if (!hasId(v) || !hasName(v)) { return false; } if (typeof v.id !== "number") { return false; } if (typeof v.name !== "string") { return false; } return true; }

10. ׂͱखؒ w asΛઈ໓ͤ͞Α ͏ ͱͨ͠Βɺ 5ZQF
    QSFEJDBUFTؔ਺͕ͨ͘ ͞Μඞཁ
    w JGϒϩοΫͷதͰ͔͠ਪ࿦͞Εͳ͍ͷͰɺ ίʔ

    υ͕ෳࡶʹͳΓ͕ͪ
    w JGϒϩοΫ͕ඞਢͳͷ͸໘౗

11. JGจΛ࢖Θͳ͍ w "TTFSUJPO
    GVODUJPOTΛ࢖͏ 

    IUUQTXXXUZQFTDSJQUMBOHPSHEPDTIBOECPPLSFMFBTFOPUFTUZQFTDSJQUIUNMBTTFSUJPOGVODUJPOT
    w function assertSomething( 


    v: unknown): asserts v is Something { ... 
 Έ͍ͨͳ΍ͭ
    w assertSomething(v)Λ࢖ͬͨΒɺ ͦͷؔ਺͕ྫ֎Λ౤͛ͳ͍ݶΓ 
 ಉҰείʔϓͷҎ߱ͷεςʔ τϝϯ τͰ͸v͕Somethingܕͱͯ͠ѻ͑Δ

12. type User = { id: number; name: string; }; function

    assertId(v: unknown): asserts v is { id: unknown } { if (typeof v !== "object" || v === null) { throw new Error("Value should be non-null object"); } if (!("id" in v)) { throw new Error('Value should have the property "id"'); } // noop } function assertName(v: unknown): asserts v is { name: unknown } { if (typeof v !== "object" || v === null) { throw new Error("Value should be non-null object"); } if (!("name" in v)) { throw new Error('Value should have the property "name"'); } // noop } function assertUser(v: unknown): asserts v is User { assertId(v); assertName(v); if (typeof v.id !== "number") { throw new Error('"id" should be a number'); } if (typeof v.name !== "string") { throw new Error('"name" should be a string'); } // noop }

13. ΍ͬͺΓखؒ w asΛઈ໓ͤ͞ΔͨΊʹ͜͜·Ͱ͢Δ ʁ
    w ҰͭͷΦϒδΣΫ τʹ͍ͭͯݕূ͢Δ͚ͩͰؔ਺ଟ͗͢͡Όͳ͍ ʁ
    

    w ΋͏asΛ࢖ͬͯ΋͍͍Μ͡Όʜ ʁ
    w ઈରʹఘΊͳ͍

14. ศརؔ਺Λ࡞ͬͯΈͨ w ϓϩύςΟ͕ੜ͍͑ͯΔ͜ͱΛϥϯλΠϜͰݕূͭͭ͠
    w ܕ΋ͪΌΜͱ෇͍ͯ͘Εͯ
    w ͔͠΋ܕఆٛΛमਖ਼ͨ͠ΒϥϯλΠϜͰ 
 ݕূ͞ΕΔϓϩύςΟ ΋௥ैͯ͠΄͍͠

15. type UnionToIntersection<U> = (U extends any ? (k: U) =>

    void : never) extends ( k: infer I ) => void ? I : never; type LastOf<T> = UnionToIntersection< T extends any ? () => T : never > extends () => infer R ? R : never; type Push<T extends any[], V> = [...T, V]; type UnionToTuple< T, L = LastOf<T>, N = [T] extends [never] ? true : false > = true extends N ? [] : Push<UnionToTuple<Exclude<T, L>>, L>; type Tuple<TItem, TLength> = [TItem, ...TItem[]] & { length: TLength; }; /** * Tuple<string, 3> ͸ [string, string, string] Λฦ͢ * ͦΕΛԠ༻ͯ͠ 'a' | 'b' Λ ['a' | 'b', 'a' | 'b'] ʹ͢Δ * * 'a' | 'b' * => ['a' | 'b', 'a' | 'b'] * 'a' | 'b' | 'c' * => ['a' | 'b' | 'c', 'a' | 'b' | 'c', 'a' | 'b' | 'c'] */ type UnionToUnionTuple<T> = Tuple<T, UnionToTuple<T>["length"]>; type TypeEq<A, B> = (<T>() => T extends A ? 1 : 2) extends <T>() => T extends B ? 1 : 2 ? true : false; type RemoveNeverProperties<T> = Pick< T, { [P in keyof T]: [T[P]] extends [never] ? never : P; }[keyof T] >; type AnyAs0<T> = { [P in keyof T]: TypeEq<T[P], any> extends true ? 0 : T[P]; }; type UnknownAs0<T> = { [P in keyof T]: TypeEq<T[P], unknown> extends true ? 0 : T[P]; }; type OptionalAsUndefined<T> = { [P in keyof T]: T[P] extends NonNullable<T[P]> ? T[P] : undefined; }; type UndefinedAsNever<T> = { [P in keyof T]-?: T[P] extends undefined ? never : T[P]; }; /** * { a?: string; b: number; c?: any; d: any } Λ * { b: number; d: any } ͚ͩʹ͢Δɻ * * AnyAs0<T> ͕ͳ͍ͱ ?: any ΁ͷରԠ͕࿙ΕΔͷͰ஫ҙɻ */ type RemoveOptionalProperties<T> = { [P in keyof RemoveNeverProperties< UndefinedAsNever<OptionalAsUndefined<UnknownAs0<AnyAs0<T>>>> >]: T[P]; }; function isObject(v: unknown): v is Record<string, unknown> { if (typeof v !== "object") { return false; } return v !== null; } function assertObject( v: unknown, target = "" ): asserts v is Record<string, unknown> { if (!isObject(v)) { throw new Error(`${target} should be object`.trim()); } } function isMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, errorPropsRef: string[], target = "" ): v is T { assertObject(v, target); if (new Set(props).size !== props.length) { throw new Error("Invalid props"); } return props .map((prop) => { if (typeof prop !== "string") { throw new Error("Invalid prop"); } const within = prop in v; if (!within) { errorPropsRef.push(prop); // mutate } return within; }) .every((flag) => flag); } export function assertMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, target = "" ): asserts v is T { const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর if (!isMatchedType(v, props, errorPropsRef, target)) { // ͜͜ʹ֘౰͢Δͱ͖ errorPropsRef ഑ྻͷத਎ʹ͸ΤϥʔՕॴ͕٧·͍ͬͯΔɻ throw new Error( `${target} should be aligned type. ${ 0 < errorPropsRef.length ? `[${errorPropsRef.join(", ")}]` : "" }`.trim() ); } }

16. .map((prop) => { if (typeof prop !== "string") { throw

    new Error("Invalid prop"); } const within = prop in v; if (!within) { errorPropsRef.push(prop); // mutate } return within; }) .every((flag) => flag); } export function assertMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, target = "" ): asserts v is T { const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর if (!isMatchedType(v, props, errorPropsRef, target)) { // ͜͜ʹ֘౰͢Δͱ͖ errorPropsRef ഑ྻͷத਎ʹ͸ΤϥʔՕॴ͕٧·͍ͬͯΔɻ throw new Error( `${target} should be aligned type. ${ 0 < errorPropsRef.length ? `[${errorPropsRef.join(", ")}]` : "" }`.trim() ); } } ͳʹΛ࡞͔ͬͨ w assertMatchedType()ؔ਺Λ࣮૷ͨ͠
    w ୈҾ਺ʹݕূ͍ͨ͠ΦϒδΣΫ τ
    w ୈҾ਺ʹݕূ͍ͨ͠ϓϩύςΟ໊ͷ഑ྻ
    w ܕύϥϝʔλʹཧ૝ͷܕఆٛΛॻ͘

17. .map((prop) => { if (typeof prop !== "string") { throw

    new Error("Invalid prop"); } const within = prop in v; if (!within) { errorPropsRef.push(prop); // mutate } return within; }) .every((flag) => flag); } export function assertMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, target = "" ): asserts v is T { const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর if (!isMatchedType(v, props, errorPropsRef, target)) { // ͜͜ʹ֘౰͢Δͱ͖ errorPropsRef ഑ྻͷத਎ʹ͸ΤϥʔՕॴ͕٧·͍ͬͯΔɻ throw new Error( `${target} should be aligned type. ${ 0 < errorPropsRef.length ? `[${errorPropsRef.join(", ")}]` : "" }`.trim() ); } } ͳʹΛ࡞͔ͬͨ w assertMatchedType()ؔ਺Λ࣮૷ͨ͠
    w ୈҾ਺ʹݕূ͍ͨ͠ΦϒδΣΫ τ
    w ୈҾ਺ʹݕূ͍ͨ͠ϓϩύςΟ໊ͷ഑ྻ
    w ܕύϥϝʔλʹཧ૝ͷܕఆٛΛॻ͘ type User = { id: number; name: string; }; const obj: unknown = { id: 1, name: "foo" }; assertMatchedType<User>(obj, ["id", "name"]); console.log(obj);

18. .map((prop) => { if (typeof prop !== "string") { throw

    new Error("Invalid prop"); } const within = prop in v; if (!within) { errorPropsRef.push(prop); // mutate } return within; }) .every((flag) => flag); } export function assertMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, target = "" ): asserts v is T { const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর if (!isMatchedType(v, props, errorPropsRef, target)) { // ͜͜ʹ֘౰͢Δͱ͖ errorPropsRef ഑ྻͷத਎ʹ͸ΤϥʔՕॴ͕٧·͍ͬͯΔɻ throw new Error( `${target} should be aligned type. ${ 0 < errorPropsRef.length ? `[${errorPropsRef.join(", ")}]` : "" }`.trim() ); } } ศརͳͱ͜Ζ w ܕఆ͕ٛมΘΔͱɺ ୈҾ਺ͰٻΊΒΕΔ 
 Ҿ਺ͷܕ͕มΘΔ
    w ܕఆ͚ٛͩ௚ͯ͠ɺ 
 ϥϯλΠϜଆ͕௚ͬͯͳ͍ঢ়گΛ๷͙ type User = { id: number; name: string; email: string; }; const obj: unknown = { id: 1, name: "foo" }; assertMatchedType<User>(obj, ["id", "name"]); console.log(obj); Argument of type '["id", "name"]' is not assignable to parameter of type 'UnionToUnionTuple<"id" | "name" | "email">'.

19. function assertObject( v: unknown, target = "" ): asserts v

    is Record<string, unknown> { if (!isObject(v)) { throw new Error(`${target} should be object`.trim()); } } function isMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, errorPropsRef: string[], target = "" ): v is T { assertObject(v, target); if (new Set(props).size !== props.length) { throw new Error("Invalid props"); } return props .map((prop) => { if (typeof prop !== "string") { throw new Error("Invalid prop"); } const within = prop in v; if (!within) { errorPropsRef.push(prop); // mutate } return within; }) .every((flag) => flag); } export function assertMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, target = "" ): asserts v is T { const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর w ศརؔ਺ΛassertObject()Λࣄલʹ 
 ࡞͓ͬͯ͘
    w ϓϩύςΟࢦఆ͸͢΂ͯϢχʔΫͰ͋Δ͜ͱΛ 
 อূ
    w ͻͱͭͻͱͭinΛ࢖ͬͯ֬ೝ
    w ͳ͚Ε͹Τϥʔࢀরʹه࿥ ϥϯλΠϜଆͷ࢓૊Έ

20. * { a?: string; b: number; c?: any; d: any

    } Λ * { b: number; d: any } ͚ͩʹ͢Δɻ * * AnyAs0<T> ͕ͳ͍ͱ ?: any ΁ͷରԠ͕࿙ΕΔͷͰ஫ҙɻ */ type RemoveOptionalProperties<T> = { [P in keyof RemoveNeverProperties< UndefinedAsNever<OptionalAsUndefined<UnknownAs0<AnyAs0<T>>>> >]: T[P]; }; function isObject(v: unknown): v is Record<string, unknown> { if (typeof v !== "object") { return false; } return v !== null; } function assertObject( v: unknown, target = "" ): asserts v is Record<string, unknown> { if (!isObject(v)) { throw new Error(`${target} should be object`.trim()); } } function isMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, errorPropsRef: string[], target = "" ): v is T { assertObject(v, target); if (new Set(props).size !== props.length) { throw new Error("Invalid props"); } return props .map((prop) => { w ศརؔ਺assertObject()͸ 
 "TTFSUJPO
    GVODUJPOTͷ 
 ͓खຊͷΑ ͏ͳؔ਺ assertObject()

21. w ͔͜͜Β5ZQF4DSJQUͷຊؾ
    w ͢΂ͯͷϓϩύςΟ Λྻڍ͍ͨ͠
    w PQUJPOBMͳϓϩύςΟ͸ݕূͨ͘͠ͳ͍
    w PQUJPOBMͳϓϩύςΟ͸ॻ͔ͳ͘ ͯ΋

    
 ίϯύΠϧΤϥʔʹͨ͘͠ͳ͍
    w ͦΕΛ͢ΔͨΊͷܕύζϧ ܕύζϧ : false; type RemoveNeverProperties<T> = Pick< T, { [P in keyof T]: [T[P]] extends [never] ? never : P; }[keyof T] >; type AnyAs0<T> = { [P in keyof T]: TypeEq<T[P], any> extends true ? 0 : T[P]; }; type UnknownAs0<T> = { [P in keyof T]: TypeEq<T[P], unknown> extends true ? 0 : T[P]; }; type OptionalAsUndefined<T> = { [P in keyof T]: T[P] extends NonNullable<T[P]> ? T[P] : undefined; }; type UndefinedAsNever<T> = { [P in keyof T]-?: T[P] extends undefined ? never : T[P]; }; /** * { a?: string; b: number; c?: any; d: any } Λ * { b: number; d: any } ͚ͩʹ͢Δɻ * * AnyAs0<T> ͕ͳ͍ͱ ?: any ΁ͷରԠ͕࿙ΕΔͷͰ஫ҙɻ */ type RemoveOptionalProperties<T> = { [P in keyof RemoveNeverProperties< UndefinedAsNever<OptionalAsUndefined<UnknownAs0<AnyAs0<T>>>> >]: T[P]; }; function isObject(v: unknown): v is Record<string, unknown> {

22. : false; type RemoveNeverProperties<T> = Pick< T, { [P in

    keyof T]: [T[P]] extends [never] ? never : P; }[keyof T] >; type AnyAs0<T> = { [P in keyof T]: TypeEq<T[P], any> extends true ? 0 : T[P]; }; type UnknownAs0<T> = { [P in keyof T]: TypeEq<T[P], unknown> extends true ? 0 : T[P]; }; type OptionalAsUndefined<T> = { [P in keyof T]: T[P] extends NonNullable<T[P]> ? T[P] : undefined; }; type UndefinedAsNever<T> = { [P in keyof T]-?: T[P] extends undefined ? never : T[P]; }; /** * { a?: string; b: number; c?: any; d: any } Λ * { b: number; d: any } ͚ͩʹ͢Δɻ * * AnyAs0<T> ͕ͳ͍ͱ ?: any ΁ͷରԠ͕࿙ΕΔͷͰ஫ҙɻ */ type RemoveOptionalProperties<T> = { [P in keyof RemoveNeverProperties< UndefinedAsNever<OptionalAsUndefined<UnknownAs0<AnyAs0<T>>>> >]: T[P]; }; function isObject(v: unknown): v is Record<string, unknown> { Ṗͷຐ๏ w AnyAs0ͱUnknownAs0Ͱɺ anyܕͱ 
 unknownܕΛҰ୴͢΂ͯ 
 0ܕ ʢ਺஋Ϧςϥϧܕʣ ʹஔ͖׵͑Δ
    w PQUJPOBMͰ͋Ε͹ 
 ͢΂ͯundefinedʹ͢Δ
    w 0ܕʹஔ͖׵͓͔͑ͯͳ͍ͱ 
 PQUJPOBM
    anyͱPQUJPOBM
    unknown͕ 
 ਖ਼͘͠ॲཧ͞Εͳ͍

23. : false; type RemoveNeverProperties<T> = Pick< T, { [P in

    keyof T]: [T[P]] extends [never] ? never : P; }[keyof T] >; type AnyAs0<T> = { [P in keyof T]: TypeEq<T[P], any> extends true ? 0 : T[P]; }; type UnknownAs0<T> = { [P in keyof T]: TypeEq<T[P], unknown> extends true ? 0 : T[P]; }; type OptionalAsUndefined<T> = { [P in keyof T]: T[P] extends NonNullable<T[P]> ? T[P] : undefined; }; type UndefinedAsNever<T> = { [P in keyof T]-?: T[P] extends undefined ? never : T[P]; }; /** * { a?: string; b: number; c?: any; d: any } Λ * { b: number; d: any } ͚ͩʹ͢Δɻ * * AnyAs0<T> ͕ͳ͍ͱ ?: any ΁ͷରԠ͕࿙ΕΔͷͰ஫ҙɻ */ type RemoveOptionalProperties<T> = { [P in keyof RemoveNeverProperties< UndefinedAsNever<OptionalAsUndefined<UnknownAs0<AnyAs0<T>>>> >]: T[P]; }; function isObject(v: unknown): v is Record<string, unknown> { Ṗͷຐ๏ w undefinedΛ͢΂ͯPQUJPOBMΛ֎ͭͭ͠ 
 neverʹஔ͖׵͑Δ
    w neverͰ͋Ε͹ɺ ͦΕΒΛ͢΂ͯ 
 Pick<T, U>Λ࢖ͬͯআڈ͢Δ
    w ͜Ε͸undefinedΛؚΊଞͷܕͰ͸ 
 ͜ͷΑ ͏ͳॲཧ͕࣮ݱͰ͖ͣ 
 neverͷΈআڈͰ͖Δ

24. ܕύζϧͷ൪ਓ w ܕύζϧΛॻ͍͍ͯΔͱ͖͸ݕূ͕ࠔ೉
    w TypeEqʻA, BʼΛ࢖ͬͯ 
 ܕςε τΛॻ͘ ͱΑ͍
    

    w AnyAs0
    UnknownAs0Ͱ΋࢖༻ > = true extends N ? [] : Push<UnionToTuple<Exclude<T, L>>, L>; type Tuple<TItem, TLength> = [TItem, ...TItem[]] & { length: TLength; }; /** * Tuple<string, 3> ͸ [string, string, string] Λฦ͢ * ͦΕΛԠ༻ͯ͠ 'a' | 'b' Λ ['a' | 'b', 'a' | 'b'] ʹ͢Δ * * 'a' | 'b' * => ['a' | 'b', 'a' | 'b'] * 'a' | 'b' | 'c' * => ['a' | 'b' | 'c', 'a' | 'b' | 'c', 'a' | 'b' | 'c'] */ type UnionToUnionTuple<T> = Tuple<T, UnionToTuple<T>["length"]>; type TypeEq<A, B> = (<T>() => T extends A ? 1 : 2) extends <T>() => T extends B ? 1 : 2 ? true : false; type RemoveNeverProperties<T> = Pick< T, { [P in keyof T]: [T[P]] extends [never] ? never : P; }[keyof T] >; type AnyAs0<T> = { [P in keyof T]: TypeEq<T[P], any> extends true ? 0 : T[P]; }; type UnknownAs0<T> = { [P in keyof T]: TypeEq<T[P], unknown> extends true ? 0 : T[P]; }; type OptionalAsUndefined<T> = { https://qiita.com/kgtkr/items/2a8290d1b1314063a524

25. type UnionToIntersection<U> = (U extends any ? (k: U) =>

    void : never) extends ( k: infer I ) => void ? I : never; type LastOf<T> = UnionToIntersection< T extends any ? () => T : never > extends () => infer R ? R : never; type Push<T extends any[], V> = [...T, V]; type UnionToTuple< T, L = LastOf<T>, N = [T] extends [never] ? true : false > = true extends N ? [] : Push<UnionToTuple<Exclude<T, L>>, L>; type Tuple<TItem, TLength> = [TItem, ...TItem[]] & { length: TLength; }; /** * Tuple<string, 3> ͸ [string, string, string] Λฦ͢ * ͦΕΛԠ༻ͯ͠ 'a' | 'b' Λ ['a' | 'b', 'a' | 'b'] ʹ͢Δ * * 'a' | 'b' * => ['a' | 'b', 'a' | 'b'] * 'a' | 'b' | 'c' * => ['a' | 'b' | 'c', 'a' | 'b' | 'c', 'a' | 'b' | 'c'] */ type UnionToUnionTuple<T> = Tuple<T, UnionToTuple<T>["length"]>; Ṗͷຐ๏ w PQUJPOBMͳϓϩύςΟ Λ͢΂ͯ 
 আڈͨ͠ͷͰɺ ࢒ΓͷඞਢϓϩύςΟ Λ 
 ྻڍ͠λϓϧͰड͚औΓ͍ͨ
    w UnionToTupleΛ࢖͑͹keyof Tͷ 
 ݁ՌΛλϓϧͱͯ͠ѻ͑Δ
    w ͔͠͠ॱෆಉͰ͋Δ ʢఆ͕ٛهड़ॱʹ 
 ͳΒͳ͍ʣ ͜ͱͰ௚ײతͰ͸ͳ͍ͨΊ 
 UnionToUnionTupleͰهड़ॱΛ 
 ࣗ༝ʹ͢Δ
    w ϥϯλΠϜͰnew Set()Λͨ͠ͷ͸ 
 ͜Εରࡦ

26. ͜Ε͕࣮ݱͰ͖Δ w ܕఆ͕ٛมΘΔͱɺ ୈҾ਺ͰٻΊΒΕΔ 
 Ҿ਺ͷܕ͕มΘΔ
    w ܕఆ͚ٛͩ௚ͯ͠ɺ 
 ϥϯλΠϜଆ͕௚ͬͯͳ͍ঢ়گΛ๷͙

    .map((prop) => { if (typeof prop !== "string") { throw new Error("Invalid prop"); } const within = prop in v; if (!within) { errorPropsRef.push(prop); // mutate } return within; }) .every((flag) => flag); } export function assertMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, target = "" ): asserts v is T { const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর if (!isMatchedType(v, props, errorPropsRef, target)) { // ͜͜ʹ֘౰͢Δͱ͖ errorPropsRef ഑ྻͷத਎ʹ͸ΤϥʔՕॴ͕٧·͍ͬͯΔɻ throw new Error( `${target} should be aligned type. ${ 0 < errorPropsRef.length ? `[${errorPropsRef.join(", ")}]` : "" }`.trim() ); } } type User = { id: number; name: string; email: string; }; const obj: unknown = { id: 1, name: "foo" }; assertMatchedType<User>(obj, ["id", "name"]); console.log(obj); Argument of type '["id", "name"]' is not assignable to parameter of type 'UnionToUnionTuple<"id" | "name" | "email">'.

27. .map((prop) => { if (typeof prop !== "string") { throw

    new Error("Invalid prop"); } const within = prop in v; if (!within) { errorPropsRef.push(prop); // mutate } return within; }) .every((flag) => flag); } export function assertMatchedType<T extends object>( v: unknown, props: UnionToUnionTuple<keyof RemoveOptionalProperties<T>>, target = "" ): asserts v is T { const errorPropsRef: string[] = []; // ࢠʹ஋Λ֨ೲͤ͞ΔͨΊͷۭ഑ྻࢀর if (!isMatchedType(v, props, errorPropsRef, target)) { // ͜͜ʹ֘౰͢Δͱ͖ errorPropsRef ഑ྻͷத਎ʹ͸ΤϥʔՕॴ͕٧·͍ͬͯΔɻ throw new Error( `${target} should be aligned type. ${ 0 < errorPropsRef.length ? `[${errorPropsRef.join(", ")}]` : "" }`.trim() ); } } ࿙Εʹ͍ͭͯ w id͕number
    name͕stringͰ͋Δ͜ͱ 
 ·Ͱ͸Έͯ͘Εͳ͍
    w Α Γ҆શʹ͍ͨ͠ͳΒ͢΂ͯͷϓϩύςΟͷܕΛ 
 unknownܕʹ͢Δͷ͕Α͍
    w ͦͷ৔߹͸assertString()
    assertNumber()ͳͲͷؔ਺ͱ૊Έ߹ΘͤΔ type User = { id: unknown; name: unknown; email: unknown; }; const obj: unknown = { id: 1, name: "foo" }; assertMatchedType<User>(obj, ["id", "name"]); console.log(obj);

28. $POEJUJPOBM
    5ZQFTΛۃΊΔͱָ͍͠ w $POEJUJPOBM
    5ZQFT͸࣮͸͔ͳΓͷදݱྗ͕͋Δ 
 IUUQTXXXUZQFTDSJQUMBOHPSHEPDTIBOECPPLDPOEJUJPOBMUZQFTIUNM
    w Ұݟݫͦ͠͏ͳܕਪ࿦Ͱ΋࣮͸ॻ͚ͨΓ͢Δ
    w $POEJUJPOBM
    5ZQFTΛۃΊΑ

    ͏
    w as͸ېࢭͰ͖Δ

29. 5IBOL
    ZPV https://gist.github.com/okunokentaro/74361c2683bd8e0f349d21ddebe189cf