fix: allow readonly arrays

radashi-org · Dec 1, 2024 · d99dd3b · d99dd3b
1 parent 9fb0370
commit d99dd3b
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Showing 2 changed files with 14 additions and 2 deletions.
diff --git a/src/array/cartesianProduct.ts b/src/array/cartesianProduct.ts
@@ -1,3 +1,5 @@
+type ReadonlyArray2D<T> = readonly (readonly T[])[]
+
 /**
  * Create an [n-ary Cartesian product](https://en.wikipedia.org/wiki/Cartesian_product#n-ary_Cartesian_product)
  * from the given arrays.
@@ -22,11 +24,13 @@
  * // ]
  * ```
  */
-export function cartesianProduct<const T extends any[][]>(
+export function cartesianProduct<const T extends ReadonlyArray2D<any>>(
   ...arrays: [...T]
 ): Array<{ [K in keyof T]: T[K][number] }>
 
-export function cartesianProduct<T extends any[][]>(...arrays: T): T[][] {
+export function cartesianProduct<T extends ReadonlyArray2D<any>>(
+  ...arrays: T
+): T[][] {
   let out: T[][] = [[]]
   for (const array of arrays) {
     const result = []

diff --git a/tests/array/cartesianProduct.test-d.ts b/tests/array/cartesianProduct.test-d.ts
@@ -20,4 +20,12 @@ describe('cartesianProduct return type', () => {
     expectTypeOf(v2).toEqualTypeOf<1 | 2>()
     expectTypeOf(v3).toEqualTypeOf<boolean>()
   })
+  test('with readonly arrays', () => {
+    const colors = ['red', 'blue'] as const
+    const sizes = [1, 2] as const
+    const result = _.cartesianProduct(colors, sizes)
+    expectTypeOf(result).toEqualTypeOf<
+      [(typeof colors)[number], (typeof sizes)[number]][]
+    >()
+  })
 })