DIP 52 - Implicit conversions

[Simen Kjærås]

On 2013-12-11 16:28, bearophile wrote:
> Simen Kjærås:
>
>> http://wiki.dlang.org/DIP52
>
>> However, given that this code compiles and works perfectly:
>>
>> void baz() {
>>    import std.typecons;
>>    Tuple!(int, int) a;
>>    Tuple!(int, "x", int, "y") b;
>>    a = b; // Implicit conversion to less specialized type.
>>    b = a; // Implicit conversion to more specialized type.
>
> I think "b = a;" is an accepts-invalid bug.

I partly agree. I want this to compile:

Tuple!(int, "x", int, "y") bar() {
     import std.typecons;
     Tuple!(int, int) a;
     return a;
}

And doing that without letting "b = a;" above compile seems 
counterintuitive and an unnecessary complexity.


>> void foo(TaggedUnion!(float, string, int, MyStruct) arg) {}
>
> Do you mean Algebraic?

Since a rewrite of Algebraic, supporting more features than the current 
version, is in progress, I chose to use a simple tagged union (which is 
what the current Algebraic is, I suppose).


> Regarding the topic of implicit conversions, I propose to warn and then
> deprecate and then disallow the following two implicit casts, that only
> cause confusion, and are of no real utility:
>
> enum Foo { A, B }
> void main() {
>      enum int i1 = 1;
>      bool b1 = i1; // deprecate
>      int i2 = Foo.A; // deprecate
> }

I agree, but feel that this is orthogonal to the DIP.

--
   Simen