fix: flat type in fx

src/Lazy/fx.ts

@@ -11,6 +11,7 @@ import join from "../join";
 import reduce from "../reduce";
 import some from "../some";
 import type Cast from "../types/Cast";
+import type { DeepFlat } from "../types/DeepFlat";
 import type IterableInfer from "../types/IterableInfer";
 import type Key from "../types/Key";
 import type { SyncReducer } from "../types/Reducer";
@@ -71,8 +72,10 @@ class FxAsyncIterable<A> {
    *
    * see {@link https://fxts.dev/docs/flat | flat}
    */
-  flat(depth?: number) {
-    return new FxAsyncIterable(flat(this.asyncIterable, depth));
+  flat<T extends number = 1>(depth?: T) {
+    return new FxAsyncIterable(
+      flat(this.asyncIterable, depth),
+    ) as FxAsyncIterable<DeepFlat<A, T>>;
   }
 
   /**
@@ -326,8 +329,10 @@ export class FxIterable<A> {
    *
    * see {@link https://fxts.dev/docs/flat | flat}
    */
-  flat(depth?: number) {
-    return new FxIterable(flat(this.iterable, depth));
+  flat<T extends number = 1>(depth?: T) {
+    const res = flat(this.iterable, depth);
+
+    return new FxIterable(res) as FxIterable<DeepFlat<A, T>>;
   }
 
   /**

src/unicodeToArray.ts

@@ -42,6 +42,7 @@ const rsSymbol = `(?:${[
 ].join("|")})`;
 
 /** Used to match [string symbols](https://mathiasbynens.be/notes/javascript-unicode). */
+// eslint-disable-next-line no-misleading-character-class
 const reUnicode = RegExp(`${rsFitz}(?=${rsFitz})|${rsSymbol + rsSeq}`, "g");
 
 /**

type-check/Lazy/flat.test.ts

@@ -1,4 +1,4 @@
-import { flat, pipe, range, toAsync } from "../../src";
+import { flat, fx, pipe, range, toArray, toAsync } from "../../src";
 import * as Test from "../../src/types/Test";
 
 const { checks, check } = Test;
@@ -29,6 +29,33 @@ const res16 = flat(
   })(),
 );
 
+const res17 = fx([1, 2]).flat().toArray();
+// prettier-ignore
+const res18 = fx([1, [2]]).flat().toArray();
+// prettier-ignore
+const res19 = fx([1, [2, [3]]]).flat().toArray();
+// prettier-ignore
+const res20 = fx([1, [2, [3]]]).flat(2).toArray();
+
+const res21 = fx(["a", "b"]).flat().toArray();
+// prettier-ignore
+const res22 = fx(['a', ['b']]).flat().toArray();
+// prettier-ignore
+const res23 = fx(['a', ['b', ['c']]]).flat().toArray();
+// prettier-ignore
+const res24 = fx(['a', ['b', ['c']]]).flat(2).toArray();
+
+// prettier-ignore
+const res25 = fx(['a', 'b']).toAsync().flat().toArray();
+// prettier-ignore
+const res26 = fx(['a', ['b']]).toAsync().flat().toArray();
+
+// prettier-ignore
+const res27 = fx(['a', ['b', ['c']]]).toAsync().flat().toArray();
+const res28 = pipe(["a", ["b", ["c"]]], toAsync, flat, toArray);
+// prettier-ignore
+const res29 = fx(['a', ['b', ['c']]]).toAsync().flat(2).toArray();
+
 checks([
   check<typeof res1, IterableIterator<never>, Test.Pass>(),
   check<typeof res2, IterableIterator<number>, Test.Pass>(),
@@ -49,4 +76,20 @@ checks([
   check<typeof res14, AsyncIterableIterator<number>, Test.Pass>(),
   check<typeof res15, AsyncIterableIterator<number | number[]>, Test.Pass>(), // prettier-ignore
   check<typeof res16, IterableIterator<number | AsyncIterableIterator<number>>, Test.Pass>(), // prettier-ignore
+
+  check<typeof res17, number[], Test.Pass>(),
+  check<typeof res18, number[], Test.Pass>(),
+  check<typeof res19, (number | number[])[], Test.Pass>(),
+  check<typeof res20, number[], Test.Pass>(),
+
+  check<typeof res21, string[], Test.Pass>(),
+  check<typeof res22, string[], Test.Pass>(),
+  check<typeof res23, (string | string[])[], Test.Pass>(),
+  check<typeof res24, string[], Test.Pass>(),
+
+  check<typeof res25, Promise<string[]>, Test.Pass>(),
+  check<typeof res26, Promise<string[]>, Test.Pass>(),
+  check<typeof res27, Promise<(string | string[])[]>, Test.Pass>(),
+  check<typeof res28, Promise<(string | string[])[]>, Test.Pass>(),
+  check<typeof res29, Promise<string[]>, Test.Pass>(),
 ]);

type-check/pipe.test.ts

@@ -138,9 +138,11 @@ const Code = {
 } as const;
 
 type Code = (typeof Code)[keyof typeof Code];
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
 const res18 = pipe({ code: Code.None }, (_: { code: Code }): Code => Code.None);
 const res19 = pipe(
   { code: Code.None },
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
   async (_: { code: Code }): Promise<Code> => Code.None,
 );