Improve typing of symToStr

src/symToStr.ts

@@ -1,4 +1,5 @@
 /** @see <https://docs.tsafe.dev/main/symtostr> */
-export function symToStr<T extends Record<string, unknown>>(wrap: T): keyof T {
+export function symToStr<T extends Record<string, unknown>>(wrap: T): Exclude<keyof T, symbol | number> {
+    // @ts-expect-error: We know better
     return Object.keys(wrap)[0];
 }

test/symToStr.types.ts

@@ -0,0 +1,32 @@
+/* eslint-disable @typescript-eslint/no-unused-vars */
+/* eslint-disable @typescript-eslint/ban-ts-comment */
+import { symToStr } from "../src/symToStr";
+import { Reflect } from "../src/Reflect";
+import { assert } from "../src/assert";
+import type { Equals } from "../src/Equals";
+
+{
+    const theName = null;
+
+    const expected = "theName" as const;
+
+    const got = symToStr({ theName });
+
+    assert<Equals<typeof expected, typeof got>>();
+}
+
+{
+    const expected = "theName" as const;
+
+    const got = symToStr({ "theName": undefined });
+
+    assert<Equals<typeof expected, typeof got>>();
+}
+
+{
+    type Expected = string;
+
+    const got = symToStr(Reflect<any>());
+
+    assert<Equals<Expected, typeof got>>();
+}