Bigint

The bigint category identifies bigint and bigint literals, and casts a string literal to a bigint literal. The predicates follow the usual type branching contract, so each one can act as a boolean check, as a filter, or as a branch selector for your own types.

For arithmetic over bigint, see Math. Every math type accepts number or bigint.

IsBigint and IsNotBigint

type IsBigint<T, $O extends $StrictOptions<$O, IsBigint.$Options> = {}>
type IsNotBigint<T, $O extends $StrictOptions<$O, IsNotBigint.$Options> = {}>

🎭 predicate — is T bigint or a bigint literal.

type R1 = IsBigint<bigint> // true
type R2 = IsBigint<1n> // true
type R3 = IsBigint<string | boolean> // false
type R4 = IsBigint<string | bigint> // boolean, distributed
type R5 = IsNotBigint<1n> // false

Both support selection: 'filter', exact: true, distributive: false, and the $any / $unknown / $never / $void branch overrides. See type branching.

type R6 = IsBigint<1n, { exact: true }> // false — `1n` is not exactly `bigint`
type R7 = IsBigint<1n, { selection: 'filter' }> // 1n
type R8 = IsBigint<string | bigint, { distributive: false }> // false

IsBigintLiteral and IsNotBigintLiteral

type IsBigintLiteral<T, $O extends $StrictOptions<$O, IsBigintLiteral.$Options> = {}>
type IsNotBigintLiteral<T, $O extends $StrictOptions<$O, IsNotBigintLiteral.$Options> = {}>

Narrower than IsBigint: only bigint literals pass.

type R1 = IsBigintLiteral<1n> // true
type R2 = IsBigintLiteral<bigint> // false
type R3 = IsNotBigintLiteral<bigint> // true
type R4 = IsNotBigintLiteral<1n | string, { selection: 'filter' }> // string

They already answer the literal question, so they do not take exact; passing it is a compile error.

StringToBigint

type StringToBigint<S extends string, $O extends $StrictOptions<$O, StringToBigint.$Options> = {}>

Casts a string literal to a bigint literal when the string is a valid bigint form, which needs the n suffix. NumericToString casts the other way and keeps the suffix; see the number casts.

type R1 = StringToBigint<'1n'> // 1n
type R2 = StringToBigint<'-1n'> // -1n
type R3 = StringToBigint<'abc'> // never