sumtype 0.5.0

[vit]

On Thursday, 9 August 2018 at 01:04:43 UTC, Paul Backus wrote:
> On Thursday, 9 August 2018 at 00:11:22 UTC, Seb wrote:
>> On Thursday, 9 August 2018 at 00:07:05 UTC, Seb wrote:
>>> (It uses the version from DUB and updates itself once daily, 
>>> but somehow dub still lists 0.4.1 at the moment)
>>
>> It looks like you didn't push the git tag to GitHub:
>>
>> https://github.com/pbackus/sumtype/releases
>
> One of these days, I'll learn. Should be there now.

SumType without initialization doesn't fail if first type has 
@disabled this().
In SumType need be something like this:

struct SumType(...){
     ///...

     static if(Types.length > 0 && __traits(compiles, (){Types[0] 
tmp;}()) == false){
         ///Types[0] has disabled this()
         @disable this();
     }

     ///....
}

method toString is not template. (why is there in the first 
place?)

SumType can have zero TypeArgs but then tryMatch fail:

auto st = SumType!();
st.tryMatch!((_) => 1);   //fail at compile time with bad error 
message.

in matchImpl can by something like this:

         static if(Types.length == 0){
             static if(exhaustive) {
                 static assert(0, "No value to match");
             } else {
                 throw new MatchException("No value to match");
             }
         }
         else{
             ///...
         }

or:

struct SumType(TypeArgs...)
if(TypeArgs.length > 0){
}