Constructor parameters of BigInt which is lost BigInt, String, Boolean, Number type

[NWYLZW]

⚙ Compilation target

ES2020

⚙ Library

TypeScript

Missing / Incorrect Definition

interface BigIntConstructor {
    // wrong
    (value: bigint | boolean | number | string): bigint;
    // right
    (value: bigint | BigInt | boolean | Boolean | number | Number | string | String): bigint;
}

Sample Code

declare const n: unknown

if (n instanceof BigInt) {
  BigInt(n)
  //     ^? TS2345: Argument of type BigInt is not assignable to parameter of type string | number | bigint | boolean
}

// ----

function foo(a: BigInt) {
  BigInt(a)
  //     ^? TS2345: Argument of type BigInt is not assignable to parameter of type string | number | bigint | boolean
}
foo(Object(BigInt(1)))

Documentation Link

We can see in 21.2.1.1 BigInt ( value ) that 2. Let prim be ? ToPrimitive(value, NUMBER). corresponds to our situation and triggers ToPrimitive.
ToPrimitive attempts to retrieve the valueOf method of the Object. For BigInt, Number, String, and Boolean, this method exists, allowing us to obtain a corresponding primitive value. Then, based on the preferredType of NUMBER, it is further converted to a number.
Our problem is essentially answered here, indicating that we should support Boxed Types as input.

about

• MDN BigInt()

[MartinJohns]

This is intentional. The usage of these wrapper objects is discouraged. This is the same as #54059.

Also see the handbook: https://www.typescriptlang.org/docs/handbook/declaration-files/do-s-and-don-ts.html#number-string-boolean-symbol-and-object

❌ Don’t ever use the types Number, String, Boolean, Symbol, or Object These types refer to non-primitive boxed objects that are almost never used appropriately in JavaScript code.

You also shouldn't use instanceof BigInt, as this check will actually fail with primitive bigints: 5n instanceof BigInt // false.

It seems you actually want #2361.

[NWYLZW]

1. I understand that TypeScript does not encourage the use of boxed types. However, as a runtime data validation module, I cannot guarantee whether the data received by the user at runtime has been boxed or not.

2. I am aware that instanceof cannot handle checks for primitive, so I have implemented an unboxing process.

https://github.com/typp-js/typp/blob/cd94af21d2c0bb9a73026df0e634e845841719e4/packages/validator/src/index.ts#L349-L353