Branded string literals revert to `string` in some cases

🔎 Search Terms

If I create a branded string literal it seems to respect the string literal in the basic case of assigning to a property, however it loses this information and just reverts to string when assigning to a property or in a template string.

It makes sense that the brand object needs to be dropped in these cases, but rather than converting to string, it should convert to the narrower literal type.

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about branded string

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/C4TwDgpgBAsiAyBLYEBOBDANgHgMpQgA8UA7AEwGcoLhVESBzAPigF4p8AyKAbwH0ARhnIAuXgF9xAbgBQAYwD2JGlHRsoAcnQbVVOEhQYcWjU1nylKwmJPr0UqAHpHUAO4LUAawoBCC8uAoEBttdQADABIedHEwh2coADN0RExffxUALzFosRIAVwBbATRxdR4AbXQAXTEADjKE5NTfIA

💻 Code

type MyLiteral<S extends string> = S & {_brand: {}};
const a = 'a' as MyLiteral<'a'>;

const x: 'a' = a; // works!
const y: 'a' = `${a}`; // fails!
const z: {a: number} = {[a]: 8} // fails!

🙁 Actual behavior

For y and z, the types don't match because a is converted to string rather than 'a'

🙂 Expected behavior

The types should match in all 3 cases, x, y, z

Additional information about the issue

No response

Start with the linked TypeScript Playground and reproduce the three assignments involving the branded literal. Trace the type checking for the template string and computed property cases, comparing them with the direct assignment. Done means both y and z accept the expected narrower literal types without regressing the existing behavior.