Merge pull request #25 from lambdalisue/fix-tuple-type

🐛 tuple should be `readonly`

Author: lambdalisue

is.ts

@@ -50,7 +50,7 @@ export function isArrayOf<T>(
 }
 
 export type TupleOf<T extends readonly Predicate<unknown>[]> = {
-  -readonly [P in keyof T]: T[P] extends Predicate<infer U> ? U : never;
+  [P in keyof T]: T[P] extends Predicate<infer U> ? U : never;
 };
 
 /**
@@ -63,7 +63,7 @@ export type TupleOf<T extends readonly Predicate<unknown>[]> = {
  * const a: unknown = [0, "a", true];
  * if (is.TupleOf(predTup)(a)) {
  *  // a is narrowed to [number, string, boolean]
- *  const _: [number, string, boolean] = a;
+ *  const _: readonly [number, string, boolean] = a;
  * }
  * ```
  *

is_test.ts

@@ -104,7 +104,7 @@ Deno.test("isTupleOf<T>", async (t) => {
     const predTup = [isNumber, isString, isBoolean] as const;
     const a: unknown = [0, "a", true];
     if (isTupleOf(predTup)(a)) {
-      const _: [number, string, boolean] = a;
+      const _: readonly [number, string, boolean] = a;
     }
   });
   await t.step("returns true on T tuple", () => {