fix(isSafeInteger): implement type predicate to narrow type to number

docs/ja/reference/compat/predicate/isSafeInteger.md

@@ -56,4 +56,5 @@ isSafeInteger(NaN); // false
 
 #### 戻り値
 
-(`boolean`): 値が安全な整数の場合は `true`、そうでなければ `false` を返します。
+(`value is number`): 値が安全な整数の場合は `true`、そうでなければ `false` を返します。  
+`true` を返す場合、TypeScript は `value` の型を `number` に絞り込みます。

docs/ko/reference/compat/predicate/isSafeInteger.md

@@ -56,4 +56,5 @@ isSafeInteger(NaN); // false
 
 #### 반환 값
 
-(`boolean`): 값이 안전한 정수이면 `true`, 아니면 `false`를 반환해요.
+(`value is number`): 값이 안전한 정수이면 `true`, 아니면 `false`를 반환해요.  
+`true`를 반환할 때, TypeScript는 `value`의 타입을 `number`로 좁혀요.

docs/reference/compat/predicate/isSafeInteger.md

@@ -56,4 +56,5 @@ isSafeInteger(NaN); // false
 
 #### Returns
 
-(`boolean`): Returns `true` if the value is a safe integer, otherwise `false`.
+(`value is number`) Returns `true` if the value is a safe integer, otherwise `false`.  
+When `true`, TypeScript narrows the type of `value` to `number`.

docs/zh_hans/reference/compat/predicate/isSafeInteger.md

@@ -54,4 +54,5 @@ isSafeInteger(NaN); // false
 
 #### 返回值
 
-(`boolean`): 如果值为安全整数则返回 `true`，否则返回 `false`。
+(`value is number`): 如果值为安全整数则返回 `true`，否则返回 `false`。  
+当返回 `true` 时，TypeScript 会将 `value` 的类型缩小为 `number`。

src/compat/predicate/isSafeInteger.spec.ts

@@ -95,7 +95,17 @@ describe('isSafeInteger function', () => {
     expect(func(symbol)).toBe(false);
   });
 
-  it('should match the type of lodash', () => {
-    expectTypeOf(isSafeInteger).toEqualTypeOf<typeof isSafeIntegerLodash>();
+  it('should be compatible with lodash type', () => {
+    const lodashFn: typeof isSafeIntegerLodash = isSafeInteger;
+    expect(lodashFn(3)).toBe(true);
+    expect(lodashFn('3')).toBe(false);
+  });
+
+  it('should work as a type predicate', () => {
+    const value: unknown = 3;
+    if (isSafeInteger(value)) {
+      expectTypeOf(value).toEqualTypeOf<number>();
+      expect(typeof value).toBe('number');
+    }
   });
 });

src/compat/predicate/isSafeInteger.ts

@@ -4,17 +4,18 @@
  * A safe integer is an integer that can be precisely represented as a `number` in JavaScript,
  * without any other integer being rounded to it.
  *
- * This function can also serve as a type predicate in TypeScript, narrowing the type of the argument to `number`.
+ * This function also serves as a type predicate in TypeScript,
+ * narrowing the type of the argument to `number`.
  *
  * @param {unknown} value - The value to check
- * @returns {boolean} `true` if `value` is an integer and between the safe values, otherwise `false`
+ * @returns {value is number} `true` if `value` is an integer and between the safe values, otherwise `false`
  *
  * @example
  * isSafeInteger(3); // Returns: true
  * isSafeInteger(Number.MIN_SAFE_INTEGER - 1); // Returns: false
  * isSafeInteger(1n); // Returns: false
  * isSafeInteger('1'); // Returns: false
  */
-export function isSafeInteger(value: any): boolean {
+export function isSafeInteger(value: unknown): value is number {
   return Number.isSafeInteger(value);
 }