Bug: Circular references not allowed for template literal types

Bug Report

🔎 Search Terms

• circularly, template literal

Related issues: #43335.

🕗 Version & Regression Information

• This changed between versions 4.0.5 and 4.1.5 (different bug before)

⏯ Playground Link

Playground link with relevant code

💻 Code

// you can have circular references in tuple types
type OneOrMoreArr0<C> = C | [C, ...OneOrMoreArr0<C>[]];
// note that
//
// type OneOrMoreArr0<C> = C | [C, OneOrMoreArr0<C>];
//
// is also valid
type OneOrMoreArr<C> = Exclude<OneOrMoreArr0<C>, C>;

const noEmptyArr: [] extends OneOrMoreArr<'*'> ? false : true = true;

const x1: OneOrMoreArr<'*'> = ['*'];
const x2: OneOrMoreArr<'*'> = ['*', '*'];
const x3: OneOrMoreArr<'*'> = ['*', '*', '*']

// but when you try and do the same thing with template literal types, you get an error
//
// "Type alias 'OneOrMoreStr0' circularly references itself."
//
// "Type 'OneOrMoreStr0' is not generic."
type OneOrMoreStr0<C extends string> = C | `${C}${OneOrMoreStr0<C>}`

// we should be able to do the above, and then have e.g.,
//
// const y1: OneOrMoreStr<'*'> = '*';
// const y2: OneOrMoreStr<'*'> = '**';
// const y3: OneOrMoreStr<'*'> = '***';


// if 'C' is the empty string, the above just reduces to:
//
// OneOrMoreStr0<''> = '';
//
// otherwise the same logic as with `OneOrMoreArr0` should apply

🙁 Actual behavior

You get the error:

    Type alias 'OneOrMoreStr0' circularly references itself.
    Type 'OneOrMoreStr0' is not generic.

🙂 Expected behavior

This should type check like with the tuple example - it's the same principle, just with template literals.

Commencez par le TypeScript Playground lié et les exemples réduits de tuples récursifs et de template literals dans l’issue. Comparez la manière dont les alias de tuples récursifs sont acceptés avec celle dont l’alias de template literal est rejeté ; le travail est terminé lorsque les exemples OneOrMoreStr passent la vérification de types sans les erreurs de référence circulaire.