Merge pull request #201 from none23/fix-const-array-filter

fix: filter error with `as const` unions

Author: mattpocock

.changeset/metal-moose-march.md

@@ -0,0 +1,7 @@
+---
+"@total-typescript/ts-reset": patch
+---
+
+@author: none23
+
+Fixed a bug where running .filter on a union of arrays would not work.

.github/workflows/main.yml

@@ -13,8 +13,6 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: pnpm/action-setup@v4
-        with:
-          version: 9
       - uses: actions/setup-node@v3
         with:
           node-version: 20.x

package.json

@@ -108,7 +108,7 @@
     "prettier": "^3.2.5",
     "tsx": "^3.14.0",
     "turbo": "^1.13.3",
-    "typescript": "^5.4.5"
+    "typescript": "^5.5.4"
   },
   "prettier": {
     "arrowParens": "always",

pnpm-lock.yaml

@@ -1,9 +1,15 @@
 /// <reference path="utils.d.ts" />
 
 interface Array<T> {
-  filter(predicate: BooleanConstructor, thisArg?: any): TSReset.NonFalsy<T>[];
+  filter<S extends T>(
+    predicate: BooleanConstructor,
+    thisArg?: any,
+  ): TSReset.NonFalsy<S>[];
 }
 
 interface ReadonlyArray<T> {
-  filter(predicate: BooleanConstructor, thisArg?: any): TSReset.NonFalsy<T>[];
+  filter<S extends T>(
+    predicate: BooleanConstructor,
+    thisArg?: any,
+  ): TSReset.NonFalsy<S>[];
 }

src/entrypoints/filter-boolean.d.ts

@@ -65,6 +65,12 @@ doNotExecute(async () => {
   );
 });
 
+doNotExecute(() => {
+  const arr: string[] | number[] = {} as any;
+
+  const result = arr.indexOf("abc");
+});
+
 // lastIndexOf
 
 doNotExecute(async () => {
@@ -131,3 +137,9 @@ doNotExecute(async () => {
     true,
   );
 });
+
+doNotExecute(() => {
+  const arr: string[] | number[] = {} as any;
+
+  const result = arr.lastIndexOf("abc");
+});

src/tests/array-index-of.ts

@@ -38,3 +38,11 @@ doNotExecute(() => {
 
   type tests = [Expect<Equal<typeof result, never[]>>];
 });
+
+doNotExecute(() => {
+  const arr: string[] | number[] = {} as any;
+
+  const result = arr.filter((x) => typeof x === "string");
+
+  type tests = [Expect<Equal<typeof result, string[]>>];
+});