Re: opCall with struct alias this

[Patric Dexheimer via Digitalmars-d-learn]

On Friday, 5 May 2017 at 13:19:03 UTC, Adam D. Ruppe wrote:

On Friday, 5 May 2017 at 13:05:35 UTC, Patric Dexheimer wrote:

[...]


You should never use static opCall. They are ambiguous with 
non-static opCall as well as with constructors. It is a buggy 
mess that should never have been in the language in the first 
place.


[...]



It make sense. Even liking of the possibilities of static opCall.
But I believe that somethings must exist to evade opCall usages 
now

like empty params ctor on structs.

Re: opCall with struct alias this

[Adam D. Ruppe via Digitalmars-d-learn]

On Friday, 5 May 2017 at 13:05:35 UTC, Patric Dexheimer wrote:

static T opCall(Args...)( Args args ){


You should never use static opCall. They are ambiguous with 
non-static opCall as well as with constructors. It is a buggy 
mess that should never have been in the language in the first 
place.



// Expected: opCall of Base!Data, but get error
// auto x = Data(10);
// opCall called. What just happened here?


It is ambiguous with a constructor call on Data. It is trying to 
construct a Data, but there's not applicable constructor so it is 
an error. Note that alias this NEVER applies to constructors (and 
since static opCall is ambiguous with constructors, that doesn't 
work either), but only works on existing objects.



// never saw anything about init as function.
auto y = Data.init(10);


T.init is an existing value used to initialize any type, so it is 
no longer a constructor and can call operator overloads


But, while this should be a non-static opCall, static opCall will 
hijack that too.



Your short code hit the two big reasons why static opCall ought 
to be deprecated and totally removed: it gets confused for ctors 
and non-static opCalls, breaking in situations where you think it 
would be them, and cannot coexist with them either.


I suggest you find some other way entirely to write the code.

opCall with struct alias this

[Patric Dexheimer via Digitalmars-d-learn]

struct Base(T){
static T opCall(Args...)( Args args ){
writeln(args);
writeln("opCall");
T t;
return t;
}
}

struct Data{
Base!Data b;
alias b this;
}

void main()
{   
// Expected: opCall of Base!Data, but get error
// auto x = Data(10);
// opCall called. What just happened here?
// never saw anything about init as function.
auto y = Data.init(10);
}