On Tue Jun 16, 2026 at 3:13 PM EEST, Alejandro Colomar wrote:
> Hi Ungureanu,
>
> On 2026-06-16T13:08:18+0300, Ungureanu Radu via Std-Proposals wrote:
>> You bring up a good point, but I think that this can be solved by making
>> it only for named parameters only. For example:
>>
>> void f(X x{5}); // OK
>> void f(X {5}); // Not allowed by the proposed syntax
>>
>> This would avoid changing the current disambiguation rules for something
>> like:
>>
>> X g(X{5});
>>
>> which would continue to be parsed as it is today. Otherwise, the
>> disambiguation would have to get even more complex and could possibly
>> break existing code.
>
> I don't know if this would be ambiguous to a compiler or not. But it
> will most certainly be ambiguous to a human.
>
>
> Have a lovely day!
> Alex

Hi Alex,

I am not so sure about this being ambiguous to readers. Let's take an
ordinary declaration for example:

 int x{5};

Here, the braces are usually understood as initializing x. Similarly,

 void f(int x{5});

can naturally be read as "x has initializer {5}".

While a parameter declaration is not an object definition, parameters
still have initialization semantics. When an argument is supplied, the
parameter is initialized with that argument. When it's not supplied,
then the parameter is initialized from the default expression.

This proposal simply expresses that initialization more directly,
without requiring the type to be repeated in the default argument
expression

Can you elaborate on the ambiguity you have in mind? I may be missing a
point of confusion here.

Best regards,
Radu