Allow return type annotations on setters

Setters can return values, so TypeScript should support declaring return types on setters.

🔎 Search Terms

setter return type

🕗 Version & Regression Information

This is the behavior in every version I tried, and I reviewed the FAQ for relevant entries

⏯ Playground Link

• Without return type: https://www.typescriptlang.org/play/?#code/MYewdgzgLgBAZiEMC8MDeAoGMIFNYBGAhgE4AUA+gJTpbYwn4CuJYMA5I1C2wG5EAbJrnYBuOgF8ME8aEiw8UKLhIQAwkTAAlZqwBqg4RBQwA8gQBWuYFAB0Ac3ymA7mAAKJEAAcVUAJ4AIrgQwCQAll5QIOQIIAA0HMQk7FS2imQ0yFkcXDww-EIisuAQIAK4tgIg9mQABorKqjDAmgAkaA0q6po63PqGwQD8HOwwAFwwAETsUJMSDLp8AxC1VKJAA
• With return type: https://www.typescriptlang.org/play/?#code/MYewdgzgLgBAZiEMC8MDeAoGMIFNYBGAhgE4AUA+gJQBcOUJAlmAObpbYwn4CuJYMAOTcofAQDciAGx65BAbg4BfDEsWhIsPFCi4SEAMJEwAJV78AatNkQUMAPIEAVrmBQAdC3z2A7mAAKJCAADnpQAJ4AIrgQwEzBUCDkCCAANELEJIJU7tpkVCjIqMLmEtZy6uAQIFK47lIgLGQABtq6+jDAxgAkaG16hsZmopblEAD8QoIwdABEglCzSlylMJIyMc1U8kA

💻 Code

const foo = {
  set bar(_) {
    return 'return value';
  }
};
const settersCanReturnValues = Object.getOwnPropertyDescriptor(foo, 'bar').set() === 'return value';
console.log(`setters can${settersCanReturnValues? '' : "'t"} return values`);

Same code, with an explicit return type:

const foo = {
  set bar(_): string {
    return 'return value';
  }
};
const settersCanReturnValues = Object.getOwnPropertyDescriptor(foo, 'bar').set() === 'return value';
console.log(`setters can${settersCanReturnValues? '' : "'t"} return values`);

🙁 Actual behavior

TypeScript compiler emits invalid JavaScript containing return type declaration syntax.

🙂 Expected behavior

TypeScript compiler supports and removes return type declarations from setters.

Additional information about the issue

Commencez par les deux exemples de TypeScript Playground et comparez le JavaScript généré pour les setters avec et sans type de retour explicite. La modification est terminée lorsque le setter annoté est compilé en JavaScript valide, avec son type de retour supprimé, tandis que l’exemple existant non annoté continue de fonctionner ; ajoutez un test de régression à la suite de tests existante du compilateur.