Type Alias IsTypeRecursive<T, P>

IsTypeRecursive: T extends any[]
    ? false
    : T extends { [key: string]: any }
        ? {
            [K in keyof T]: IsTypeExtendedInList<T[K], P> extends true
                ? true
                : IsTypeRecursive<T[K], [...P, T]>
        }[keyof T] extends false
            ? false
            : true
        : IsTypeExtendedInList<T, P>

Type Guard: detect if a type is recursive.

Type Parameters

T
A type to be inspected
P extends any[] = []
(Optional) The list of parents types

Remarks

Recursively inspects the structure of T to detect if a type is recursive.

Potentially recursive types, such as union types with a parent type, are considered recursion.

Returns

true if T is recursive. false if T is not recursive. boolean if T is a union type with a recursive type.

Example

type RecursiveType = { r: RecursiveType };
type Recursive = IsTypeRecursive< RecursiveType >;                                // true

type PotentialRecursiveType = { r: PotentialRecursiveType | null };
type PotentialRecursive = IsTypeRecursive< PotentialRecursiveType >;              // true             
type IsNotRecursive = IsTypeRecursive< { a: { a: { a: { a: { a: 'a' } } } } } >;  // false