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Sep 8, 2021
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Tail recursive evaluation of conditional types #45711

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1610e19
Implement tail-recursion for conditional types and lower general inst…
ahejlsberg Sep 2, 2021
093f76a
Add tests
ahejlsberg Sep 3, 2021
a4224d6
Skip caching for tail recursive temporary conditional types
ahejlsberg Sep 4, 2021
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Add tests
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@ahejlsberg
ahejlsberg committed Sep 3, 2021
commit 093f76af3b71fe627724c898ac4189ecce89781d
49 changes: 49 additions & 0 deletions tests/baselines/reference/tailRecursiveConditionalTypes.js
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//// [tailRecursiveConditionalTypes.ts]
type Trim<S extends string> =
S extends ` ${infer T}` ? Trim<T> :
S extends `${infer T} ` ? Trim<T> :
S;

type T10 = Trim<' hello '>;
type T11 = Trim<' hello '>;

type GetChars<S> = GetCharsRec<S, never>;
type GetCharsRec<S, Acc> =
S extends `${infer Char}${infer Rest}` ? GetCharsRec<Rest, Char | Acc> : Acc;

type T20 = GetChars<'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'>;

type Reverse<T> = any[] extends T ? T : ReverseRec<T, []>;
type ReverseRec<T, Acc extends unknown[]> =
T extends [infer Head, ...infer Tail] ? ReverseRec<Tail, [Head, ...Acc]> : Acc;

type T30 = Reverse<[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>;
type T31 = Reverse<string[]>;

type TupleOf<T, N extends number> = number extends N ? T[] : TupleOfRec<T, N, []>;
type TupleOfRec<T, N extends number, Acc extends unknown[]> =
Acc["length"] extends N ? Acc : TupleOfRec<T, N, [T, ...Acc]>;

type T40 = TupleOf<any, 200>;
type T41 = TupleOf<any, number>;


//// [tailRecursiveConditionalTypes.js]
"use strict";


//// [tailRecursiveConditionalTypes.d.ts]
declare type Trim<S extends string> = S extends ` ${infer T}` ? Trim<T> : S extends `${infer T} ` ? Trim<T> : S;
declare type T10 = Trim<' hello '>;
declare type T11 = Trim<' hello '>;
declare type GetChars<S> = GetCharsRec<S, never>;
declare type GetCharsRec<S, Acc> = S extends `${infer Char}${infer Rest}` ? GetCharsRec<Rest, Char | Acc> : Acc;
declare type T20 = GetChars<'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'>;
declare type Reverse<T> = any[] extends T ? T : ReverseRec<T, []>;
declare type ReverseRec<T, Acc extends unknown[]> = T extends [infer Head, ...infer Tail] ? ReverseRec<Tail, [Head, ...Acc]> : Acc;
declare type T30 = Reverse<[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>;
declare type T31 = Reverse<string[]>;
declare type TupleOf<T, N extends number> = number extends N ? T[] : TupleOfRec<T, N, []>;
declare type TupleOfRec<T, N extends number, Acc extends unknown[]> = Acc["length"] extends N ? Acc : TupleOfRec<T, N, [T, ...Acc]>;
declare type T40 = TupleOf<any, 200>;
declare type T41 = TupleOf<any, number>;
118 changes: 118 additions & 0 deletions tests/baselines/reference/tailRecursiveConditionalTypes.symbols
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=== tests/cases/compiler/tailRecursiveConditionalTypes.ts ===
type Trim<S extends string> =
>Trim : Symbol(Trim, Decl(tailRecursiveConditionalTypes.ts, 0, 0))
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 0, 10))

S extends ` ${infer T}` ? Trim<T> :
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 0, 10))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 1, 23))
>Trim : Symbol(Trim, Decl(tailRecursiveConditionalTypes.ts, 0, 0))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 1, 23))

S extends `${infer T} ` ? Trim<T> :
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 0, 10))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 2, 22))
>Trim : Symbol(Trim, Decl(tailRecursiveConditionalTypes.ts, 0, 0))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 2, 22))

S;
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 0, 10))

type T10 = Trim<' hello '>;
>T10 : Symbol(T10, Decl(tailRecursiveConditionalTypes.ts, 3, 6))
>Trim : Symbol(Trim, Decl(tailRecursiveConditionalTypes.ts, 0, 0))

type T11 = Trim<' hello '>;
>T11 : Symbol(T11, Decl(tailRecursiveConditionalTypes.ts, 5, 170))
>Trim : Symbol(Trim, Decl(tailRecursiveConditionalTypes.ts, 0, 0))

type GetChars<S> = GetCharsRec<S, never>;
>GetChars : Symbol(GetChars, Decl(tailRecursiveConditionalTypes.ts, 6, 170))
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 8, 14))
>GetCharsRec : Symbol(GetCharsRec, Decl(tailRecursiveConditionalTypes.ts, 8, 41))
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 8, 14))

type GetCharsRec<S, Acc> =
>GetCharsRec : Symbol(GetCharsRec, Decl(tailRecursiveConditionalTypes.ts, 8, 41))
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 9, 17))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 9, 19))

S extends `${infer Char}${infer Rest}` ? GetCharsRec<Rest, Char | Acc> : Acc;
>S : Symbol(S, Decl(tailRecursiveConditionalTypes.ts, 9, 17))
>Char : Symbol(Char, Decl(tailRecursiveConditionalTypes.ts, 10, 22))
>Rest : Symbol(Rest, Decl(tailRecursiveConditionalTypes.ts, 10, 35))
>GetCharsRec : Symbol(GetCharsRec, Decl(tailRecursiveConditionalTypes.ts, 8, 41))
>Rest : Symbol(Rest, Decl(tailRecursiveConditionalTypes.ts, 10, 35))
>Char : Symbol(Char, Decl(tailRecursiveConditionalTypes.ts, 10, 22))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 9, 19))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 9, 19))

type T20 = GetChars<'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'>;
>T20 : Symbol(T20, Decl(tailRecursiveConditionalTypes.ts, 10, 81))
>GetChars : Symbol(GetChars, Decl(tailRecursiveConditionalTypes.ts, 6, 170))

type Reverse<T> = any[] extends T ? T : ReverseRec<T, []>;
>Reverse : Symbol(Reverse, Decl(tailRecursiveConditionalTypes.ts, 12, 86))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 14, 13))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 14, 13))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 14, 13))
>ReverseRec : Symbol(ReverseRec, Decl(tailRecursiveConditionalTypes.ts, 14, 58))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 14, 13))

type ReverseRec<T, Acc extends unknown[]> =
>ReverseRec : Symbol(ReverseRec, Decl(tailRecursiveConditionalTypes.ts, 14, 58))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 15, 16))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 15, 18))

T extends [infer Head, ...infer Tail] ? ReverseRec<Tail, [Head, ...Acc]> : Acc;
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 15, 16))
>Head : Symbol(Head, Decl(tailRecursiveConditionalTypes.ts, 16, 20))
>Tail : Symbol(Tail, Decl(tailRecursiveConditionalTypes.ts, 16, 35))
>ReverseRec : Symbol(ReverseRec, Decl(tailRecursiveConditionalTypes.ts, 14, 58))
>Tail : Symbol(Tail, Decl(tailRecursiveConditionalTypes.ts, 16, 35))
>Head : Symbol(Head, Decl(tailRecursiveConditionalTypes.ts, 16, 20))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 15, 18))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 15, 18))

type T30 = Reverse<[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>;
>T30 : Symbol(T30, Decl(tailRecursiveConditionalTypes.ts, 16, 83))
>Reverse : Symbol(Reverse, Decl(tailRecursiveConditionalTypes.ts, 12, 86))

type T31 = Reverse<string[]>;
>T31 : Symbol(T31, Decl(tailRecursiveConditionalTypes.ts, 18, 171))
>Reverse : Symbol(Reverse, Decl(tailRecursiveConditionalTypes.ts, 12, 86))

type TupleOf<T, N extends number> = number extends N ? T[] : TupleOfRec<T, N, []>;
>TupleOf : Symbol(TupleOf, Decl(tailRecursiveConditionalTypes.ts, 19, 29))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 21, 13))
>N : Symbol(N, Decl(tailRecursiveConditionalTypes.ts, 21, 15))
>N : Symbol(N, Decl(tailRecursiveConditionalTypes.ts, 21, 15))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 21, 13))
>TupleOfRec : Symbol(TupleOfRec, Decl(tailRecursiveConditionalTypes.ts, 21, 82))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 21, 13))
>N : Symbol(N, Decl(tailRecursiveConditionalTypes.ts, 21, 15))

type TupleOfRec<T, N extends number, Acc extends unknown[]> =
>TupleOfRec : Symbol(TupleOfRec, Decl(tailRecursiveConditionalTypes.ts, 21, 82))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 22, 16))
>N : Symbol(N, Decl(tailRecursiveConditionalTypes.ts, 22, 18))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 22, 36))

Acc["length"] extends N ? Acc : TupleOfRec<T, N, [T, ...Acc]>;
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 22, 36))
>N : Symbol(N, Decl(tailRecursiveConditionalTypes.ts, 22, 18))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 22, 36))
>TupleOfRec : Symbol(TupleOfRec, Decl(tailRecursiveConditionalTypes.ts, 21, 82))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 22, 16))
>N : Symbol(N, Decl(tailRecursiveConditionalTypes.ts, 22, 18))
>T : Symbol(T, Decl(tailRecursiveConditionalTypes.ts, 22, 16))
>Acc : Symbol(Acc, Decl(tailRecursiveConditionalTypes.ts, 22, 36))

type T40 = TupleOf<any, 200>;
>T40 : Symbol(T40, Decl(tailRecursiveConditionalTypes.ts, 23, 66))
>TupleOf : Symbol(TupleOf, Decl(tailRecursiveConditionalTypes.ts, 19, 29))

type T41 = TupleOf<any, number>;
>T41 : Symbol(T41, Decl(tailRecursiveConditionalTypes.ts, 25, 29))
>TupleOf : Symbol(TupleOf, Decl(tailRecursiveConditionalTypes.ts, 19, 29))

53 changes: 53 additions & 0 deletions tests/baselines/reference/tailRecursiveConditionalTypes.types
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=== tests/cases/compiler/tailRecursiveConditionalTypes.ts ===
type Trim<S extends string> =
>Trim : Trim<S>

S extends ` ${infer T}` ? Trim<T> :
S extends `${infer T} ` ? Trim<T> :
S;

type T10 = Trim<' hello '>;
>T10 : "hello"

type T11 = Trim<' hello '>;
>T11 : "hello"

type GetChars<S> = GetCharsRec<S, never>;
>GetChars : GetChars<S>

type GetCharsRec<S, Acc> =
>GetCharsRec : GetCharsRec<S, Acc>

S extends `${infer Char}${infer Rest}` ? GetCharsRec<Rest, Char | Acc> : Acc;

type T20 = GetChars<'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'>;
>T20 : "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z" | "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z" | "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"

type Reverse<T> = any[] extends T ? T : ReverseRec<T, []>;
>Reverse : Reverse<T>

type ReverseRec<T, Acc extends unknown[]> =
>ReverseRec : ReverseRec<T, Acc>

T extends [infer Head, ...infer Tail] ? ReverseRec<Tail, [Head, ...Acc]> : Acc;

type T30 = Reverse<[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>;
>T30 : [9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

type T31 = Reverse<string[]>;
>T31 : string[]

type TupleOf<T, N extends number> = number extends N ? T[] : TupleOfRec<T, N, []>;
>TupleOf : TupleOf<T, N>

type TupleOfRec<T, N extends number, Acc extends unknown[]> =
>TupleOfRec : TupleOfRec<T, N, Acc>

Acc["length"] extends N ? Acc : TupleOfRec<T, N, [T, ...Acc]>;

type T40 = TupleOf<any, 200>;
>T40 : [any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any, any]

type T41 = TupleOf<any, number>;
>T41 : any[]

30 changes: 30 additions & 0 deletions tests/cases/compiler/tailRecursiveConditionalTypes.ts
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// @strict: true
// @declaration: true

type Trim<S extends string> =
S extends ` ${infer T}` ? Trim<T> :
S extends `${infer T} ` ? Trim<T> :
S;

type T10 = Trim<' hello '>;
type T11 = Trim<' hello '>;

type GetChars<S> = GetCharsRec<S, never>;
type GetCharsRec<S, Acc> =
S extends `${infer Char}${infer Rest}` ? GetCharsRec<Rest, Char | Acc> : Acc;

type T20 = GetChars<'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'>;

type Reverse<T> = any[] extends T ? T : ReverseRec<T, []>;
type ReverseRec<T, Acc extends unknown[]> =
T extends [infer Head, ...infer Tail] ? ReverseRec<Tail, [Head, ...Acc]> : Acc;

type T30 = Reverse<[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>;
type T31 = Reverse<string[]>;

type TupleOf<T, N extends number> = number extends N ? T[] : TupleOfRec<T, N, []>;
type TupleOfRec<T, N extends number, Acc extends unknown[]> =
Acc["length"] extends N ? Acc : TupleOfRec<T, N, [T, ...Acc]>;

type T40 = TupleOf<any, 200>;
type T41 = TupleOf<any, number>;
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