ArraySlice: Support array spread (#832)

sindresorhus · Mar 19, 2024 · d2d0d01 · d2d0d01
1 parent bc49577
commit d2d0d01
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Showing 6 changed files with 118 additions and 73 deletions.
diff --git a/source/array-slice.d.ts b/source/array-slice.d.ts
@@ -1,9 +1,11 @@
 import type {Sum} from './sum';
-import type {LessThan} from './less-than';
 import type {LessThanOrEqual} from './less-than-or-equal';
+import type {GreaterThanOrEqual} from './greater-than-or-equal';
+import type {GreaterThan} from './greater-than';
 import type {IsNegative} from './numeric';
-import type {And} from './internal';
+import type {And, Not, ArrayMin} from './internal';
 import type {IsEqual} from './is-equal';
+import type {ArraySplice} from './array-splice';
 
 /**
 Returns an array slice of a given range, just like `Array#slice()`.
@@ -54,9 +56,26 @@ slice[3];
 */
 export type ArraySlice<
 	Array_ extends readonly unknown[],
-	Start extends number = 0,
-	End extends number = Array_['length'],
-> = ArraySliceHelper<Array_, Start, End>;
+	Start extends number = never,
+	End extends number = never,
+> = And<IsEqual<Start, never>, IsEqual<End, never>> extends true
+	? Array_
+	: number extends Array_['length']
+		? VariableLengthArraySliceHelper<Array_, Start, End>
+		: ArraySliceHelper<Array_, IsEqual<Start, never> extends true ? 0 : Start, IsEqual<End, never> extends true ? Array_['length'] : End>;
+
+type VariableLengthArraySliceHelper<
+	Array_ extends readonly unknown[],
+	Start extends number,
+	End extends number,
+> = And<Not<IsNegative<Start>>, IsEqual<End, never>> extends true
+	? ArraySplice<Array_, 0, Start>
+	: And<
+	And<Not<IsNegative<Start>>, Not<IsNegative<End>>>,
+	IsEqual<GreaterThan<End, Start>, true>
+	> extends true
+		? ArraySliceByPositiveIndex<Array_, Start, End>
+		: [];
 
 type ArraySliceHelper<
 	Array_ extends readonly unknown[],
@@ -73,21 +92,15 @@ type ArraySliceHelper<
 			: never
 		: Start,
 	PositiveE extends number = IsNegative<End> extends true ? Sum<ArrayLength, End> : End,
-> = true extends [IsNegative<PositiveS>, LessThanOrEqual<PositiveE, PositiveS>][number]
+> = true extends [IsNegative<PositiveS>, LessThanOrEqual<PositiveE, PositiveS>, GreaterThanOrEqual<PositiveS, ArrayLength>][number]
 	? []
-	: ArraySliceByPositiveIndex<Array_, PositiveS, PositiveE>;
+	: ArraySliceByPositiveIndex<Array_, ArrayMin<[PositiveS, ArrayLength]>, ArrayMin<[PositiveE, ArrayLength]>>;
 
 type ArraySliceByPositiveIndex<
 	Array_ extends readonly unknown[],
 	Start extends number,
 	End extends number,
-	TraversedElement extends Array<Array_[number]> = [],
 	Result extends Array<Array_[number]> = [],
-> = Array_ extends readonly [infer H, ...infer Rest]
-	? And<
-	IsEqual<LessThanOrEqual<Start, TraversedElement['length']>, true>,
-	IsEqual<LessThan<TraversedElement['length'], End>, true>
-	> extends true
-		? ArraySliceByPositiveIndex<Rest, Start, End, [...TraversedElement, H], [...Result, H]>
-		: ArraySliceByPositiveIndex<Rest, Start, End, [...TraversedElement, H], Result>
-	: Result;
+> = Start extends End
+	? Result
+	: ArraySliceByPositiveIndex<Array_, Sum<Start, 1>, End, [...Result, Array_[Start]]>;
diff --git a/source/subtract.d.ts b/source/subtract.d.ts
@@ -34,33 +34,35 @@ Subtract<PositiveInfinity, PositiveInfinity>;
 @category Numeric
 */
 // TODO: Support big integer and negative number.
-export type Subtract<A extends number, B extends number> = [
-	IsEqual<A, PositiveInfinity>, IsEqual<A, NegativeInfinity>,
-	IsEqual<B, PositiveInfinity>, IsEqual<B, NegativeInfinity>,
-] extends infer R extends [boolean, boolean, boolean, boolean]
-	? Or<
-	And<IsEqual<R[0], true>, IsEqual<R[2], false>>,
-	And<IsEqual<R[3], true>, IsEqual<R[1], false>>
-	> extends true
-		? PositiveInfinity
-		: Or<
-		And<IsEqual<R[1], true>, IsEqual<R[3], false>>,
-		And<IsEqual<R[2], true>, IsEqual<R[0], false>>
+export type Subtract<A extends number, B extends number> = number extends A | B
+	? number
+	: [
+		IsEqual<A, PositiveInfinity>, IsEqual<A, NegativeInfinity>,
+		IsEqual<B, PositiveInfinity>, IsEqual<B, NegativeInfinity>,
+	] extends infer R extends [boolean, boolean, boolean, boolean]
+		? Or<
+		And<IsEqual<R[0], true>, IsEqual<R[2], false>>,
+		And<IsEqual<R[3], true>, IsEqual<R[1], false>>
 		> extends true
-			? NegativeInfinity
-			: true extends R[number]
-				? number
-				: [IsNegative<A>, IsNegative<B>] extends infer R
-					? [false, false] extends R
-						? BuildTuple<A> extends infer R
-							? R extends [...BuildTuple<B>, ...infer R]
-								? R['length']
-								: number
-							: never
-						: LessThan<A, B> extends true
-							? number
-							: [false, true] extends R
-								? Sum<A, NumberAbsolute<B>>
-								: Subtract<NumberAbsolute<B>, NumberAbsolute<A>>
-					: never
-	: never;
+			? PositiveInfinity
+			: Or<
+			And<IsEqual<R[1], true>, IsEqual<R[3], false>>,
+			And<IsEqual<R[2], true>, IsEqual<R[0], false>>
+			> extends true
+				? NegativeInfinity
+				: true extends R[number]
+					? number
+					: [IsNegative<A>, IsNegative<B>] extends infer R
+						? [false, false] extends R
+							? BuildTuple<A> extends infer R
+								? R extends [...BuildTuple<B>, ...infer R]
+									? R['length']
+									: number
+								: never
+							: LessThan<A, B> extends true
+								? number
+								: [false, true] extends R
+									? Sum<A, NumberAbsolute<B>>
+									: Subtract<NumberAbsolute<B>, NumberAbsolute<A>>
+						: never
+		: never;
diff --git a/source/sum.d.ts b/source/sum.d.ts
@@ -34,33 +34,35 @@ Sum<PositiveInfinity, NegativeInfinity>;
 @category Numeric
 */
 // TODO: Support big integer and negative number.
-export type Sum<A extends number, B extends number> = [
-	IsEqual<A, PositiveInfinity>, IsEqual<A, NegativeInfinity>,
-	IsEqual<B, PositiveInfinity>, IsEqual<B, NegativeInfinity>,
-] extends infer R extends [boolean, boolean, boolean, boolean]
-	? Or<
-	And<IsEqual<R[0], true>, IsEqual<R[3], false>>,
-	And<IsEqual<R[2], true>, IsEqual<R[1], false>>
-	> extends true
-		? PositiveInfinity
-		: Or<
-		And<IsEqual<R[1], true>, IsEqual<R[2], false>>,
-		And<IsEqual<R[3], true>, IsEqual<R[0], false>>
+export type Sum<A extends number, B extends number> = number extends A | B
+	? number
+	: [
+		IsEqual<A, PositiveInfinity>, IsEqual<A, NegativeInfinity>,
+		IsEqual<B, PositiveInfinity>, IsEqual<B, NegativeInfinity>,
+	] extends infer R extends [boolean, boolean, boolean, boolean]
+		? Or<
+		And<IsEqual<R[0], true>, IsEqual<R[3], false>>,
+		And<IsEqual<R[2], true>, IsEqual<R[1], false>>
 		> extends true
-			? NegativeInfinity
-			: true extends R[number]
-				? number
-				: ([IsNegative<A>, IsNegative<B>] extends infer R
-					? [false, false] extends R
-						? [...BuildTuple<A>, ...BuildTuple<B>]['length']
-						: [true, true] extends R
-							? number
-							: ArrayMax<[NumberAbsolute<A>, NumberAbsolute<B>]> extends infer Max_
-								? ArrayMin<[NumberAbsolute<A>, NumberAbsolute<B>]> extends infer Min_ extends number
-									? Max_ extends A | B
-										? Subtract<Max_, Min_>
-										: number
+			? PositiveInfinity
+			: Or<
+			And<IsEqual<R[1], true>, IsEqual<R[2], false>>,
+			And<IsEqual<R[3], true>, IsEqual<R[0], false>>
+			> extends true
+				? NegativeInfinity
+				: true extends R[number]
+					? number
+					: ([IsNegative<A>, IsNegative<B>] extends infer R
+						? [false, false] extends R
+							? [...BuildTuple<A>, ...BuildTuple<B>]['length']
+							: [true, true] extends R
+								? number
+								: ArrayMax<[NumberAbsolute<A>, NumberAbsolute<B>]> extends infer Max_
+									? ArrayMin<[NumberAbsolute<A>, NumberAbsolute<B>]> extends infer Min_ extends number
+										? Max_ extends A | B
+											? Subtract<Max_, Min_>
+											: number
+										: never
 									: never
-								: never
-					: never) & number
-	: never;
+						: never) & number
+		: never;
diff --git a/test-d/array-slice.ts b/test-d/array-slice.ts
@@ -18,3 +18,21 @@ expectType<ArraySlice<[0, 1, 2, 3], 0, -3>>([0]);
 expectType<ArraySlice<[0, 1, 2, 3], 0, -4>>([]);
 expectType<ArraySlice<[], -10, 1>>([]);
 expectType<ArraySlice<[]>>([]);
+
+expectType<ArraySlice<[...string[], 1, 2]>>([...(null! as string[]), 1, 2]);
+expectType<ArraySlice<[...string[], 1, 2], 0>>([...(null! as string[]), 1, 2]);
+expectType<ArraySlice<[...string[], 1, 2], 0, 2>>([null! as (string | 1 | 2), null! as (string | 1 | 2)]);
+expectType<ArraySlice<[...string[], 1, 2], 1, 4>>([null! as (string | 1 | 2), null! as (string | 1 | 2), null! as (string | 1 | 2)]);
+
+expectType<ArraySlice<[1, 2, 3, ...string[]]>>([1, 2, 3, ...(null! as string[])]);
+expectType<ArraySlice<[1, 2, 3, ...string[]], 0>>([1, 2, 3, ...(null! as string[])]);
+expectType<ArraySlice<[1, 2, 3, ...string[]], 0, 3>>([1, 2, 3]);
+expectType<ArraySlice<[1, 2, 3, ...string[]], 1, 5>>([2, 3, null! as string, null! as string]);
+
+expectType<ArraySlice<[1, 2, 3, ...string[], 4, 5]>>([1, 2, 3, ...(null! as string[]), 4, 5]);
+expectType<ArraySlice<[1, 2, 3, ...string[], 4, 5], 0>>([1, 2, 3, ...(null! as string[]), 4, 5]);
+expectType<ArraySlice<[1, 2, 3, ...string[], 4, 5], 1, 5>>([2, 3, null! as (string | 4 | 5), null! as (string | 4 | 5)]);
+expectType<ArraySlice<[1, 2, 3, ...string[], 4, 5], 0>>([1, 2, 3, ...(null! as string[]), 4, 5]);
+expectType<ArraySlice<[1, 2, 3, ...string[], 4, 5], 1>>([2, 3, ...(null! as string[]), 4, 5]);
+expectType<ArraySlice<[1, 2, 3, ...string[], 4, 5], 3>>([...(null! as string[]), 4, 5]);
+expectType<ArraySlice<[1, 2, 3, ...string[], 4, 5], 10>>([...(null! as string[]), 4, 5]);
diff --git a/test-d/subtract.ts b/test-d/subtract.ts
@@ -15,3 +15,8 @@ expectType<Subtract<999, NegativeInfinity>>(null! as PositiveInfinity);
 expectType<Subtract<NegativeInfinity, PositiveInfinity>>(null! as NegativeInfinity);
 expectType<Subtract<NegativeInfinity, NegativeInfinity>>(null! as number);
 expectType<Subtract<PositiveInfinity, PositiveInfinity>>(null! as number);
+
+expectType<Subtract<number, 2>>(null! as number);
+expectType<Subtract<2, number>>(null! as number);
+expectType<Subtract<number, number>>(null! as number);
+expectType<Subtract<number, PositiveInfinity>>(null! as number);
diff --git a/test-d/sum.ts b/test-d/sum.ts
@@ -13,3 +13,8 @@ expectType<Sum<-999, PositiveInfinity>>(null! as PositiveInfinity);
 expectType<Sum<NegativeInfinity, 999>>(null! as NegativeInfinity);
 expectType<Sum<999, NegativeInfinity>>(null! as NegativeInfinity);
 expectType<Sum<NegativeInfinity, PositiveInfinity>>(null! as number);
+
+expectType<Sum<number, 1>>(null! as number);
+expectType<Sum<1, number>>(null! as number);
+expectType<Sum<number, number>>(null! as number);
+expectType<Sum<number, PositiveInfinity>>(null! as number);