DIP 1031--Deprecate Brace-Style Struct Initializers--Community Review Round 1 Discussion

[Steven Schveighoffer]

On 2/13/20 10:49 AM, IGotD- wrote:
> On Thursday, 13 February 2020 at 13:05:19 UTC, Steven Schveighoffer wrote:
>>
>> That page is *really* old. I think what Mike meant to say is that 
>> struct initializers and struct literals are both disabled once a 
>> constructor or opCall function is present.
>>
>> So in essence, the above struct S could NEVER be initialized except 
>> via constructor or with it's .init value. Having the named parameter 
>> DIP accepted means that now the constructor becomes possible to call 
>> like the initializer, assuming you gave bp and ap default values.
>>
> 
> Isn't that a bit restrictive? Wouldn't you like to have a constructor 
> and sometimes parenthesis style initialization? With using parenthesis 
> for everything there will be an ambiguity. In that case keeping () for 
> constructor and {} for initialization would make it clear what the 
> programmer wants.
> 
> If the compiler cannot match a constructor it can go on and use 
> initialization instead. Would this be too allowing and lead to that 
> programmer errors are missed?

You misunderstand.

{} intialization today does not work when a constructor is defined:

struct S
{
    int a;
    this(int a) {this.a = a; }
}

void main()
{
    S s = {a: 1};
}

Error: struct S has constructors, cannot use { initializers }, use S( 
initializers ) instead

So the only place this DIP would deprecate valid code is for structs 
without ctors.

-Steve