[isolatedDeclarations] Type of const variable declared with template literal expression containing only literals still requires explicit annotation

🔎 Search Terms

isolated declarations template literal expression

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play/?isolatedDeclarations=true&ts=5.6.0-dev.20240705#code/KYDwDg9gTgLgBAG2PAZhCcC8cAGASAbwHIiBfHAbgCgrRJY4BjCAOwGd4AjAQyi10Ily1WuGioAri0YwAlqzg8AXgAoAlHAJU4OuFGQSoLAcTKUqpIA

💻 Code

export let foo = `${''}`;

export const bar = `${''}`;

export function baz() {
    return `${''}`;
}

🙁 Actual behavior

bar has a type error:

Variable must have an explicit type annotation with --isolatedDeclarations.(9010)
input.tsx(3, 14): Add a type annotation to the variable bar.

foo would also have a type error if as const was added to the expression.

🙂 Expected behavior

No type error

Additional information about the issue

fun fact: I accidentally discovered this behavior when I found that oxc-transform has type errors for both const, let, and return types.

Comienza con el TypeScript Playground enlazado y reproduce el diagnóstico de isolatedDeclarations para la const exportada; después compáralo con los ejemplos de let y function del issue. Sigue la ruta del compilador responsable de inferir los tipos de estas declaraciones; el trabajo estará terminado cuando la expresión de plantilla compuesta únicamente por literales ya no requiera una anotación explícita y los casos existentes sigan siendo correctos.