Le 3 févr. 2014 à 19:39, Brandon Benvie <bbenvie at mozilla.com> a écrit :

> On 2/3/2014 10:22 AM, Claude Pache wrote:
>> Therefore, it would be nice if `return expression` would be statically forbidden in the `constructor` method when defined using the `class` syntax (but a bare `return` is fine, which slightly complicates the grammar).
> 
> I like the motivation, but doing it as an early error is problematic (having experienced a validator that differentiates between `return`, `return undefined`, and `return void expr` and complains loudly).
> 
> Instead I would suggest to throw an error at runtime if a class constructor returns anything besides undefined when it is constructed.

I don't see much advantage in being allowed to write `return someExpressionThatShouldYieldUndefined`. Indeed, you can always write `someExpressionThatShouldYieldUndefined; return`, or even: `if (someExpressionThatShouldYieldUndefined !== undefined) throw new TypeError; return`.

Also, the problem, with runtime exception, is that we are no longer able to easily differentiate between `construct` methods that are defined using the `class` syntax and other `construct` methods... which raise the issue of backward compatibility.

—Claude

Le 3 févr. 2014 à 19:39, Brandon Benvie <bbenvie at mozilla.com> a écrit :

> I like the motivation, but doing it as an early error is problematic (having experienced a validator that differentiates between `return`, `return undefined`, and `return void expr` and complains loudly).
> 
> Instead I would suggest to throw an error at runtime if a class constructor returns anything besides undefined when it is constructed.

I don't see much advantage in being allowed to write `return someExpressionThatShouldYieldUndefined`. Indeed, you can always write `someExpressionThatShouldYieldUndefined; return`, or even: `if (someExpressionThatShouldYieldUndefined !== undefined) throw new TypeError; return`.

Also, the problem, with runtime exception, is that we are no longer able to easily differentiate between `construct` methods that are defined using the `class` syntax and other `construct` methods... which raise the issue of backward compatibility.