Why does this work?

[hane via Digitalmars-d-learn]

On Monday, 23 June 2014 at 08:30:44 UTC, h_zet wrote:
> import std.typecons;
>
> auto foo2(R)(R foopara){
>     return tuple(foopara, is(R==int));
> }
>
> void main(){
>     auto tuple(a,b) = foo2(1);
> }
>
>
> I'm expecting some error such as can not act as left value but 
> when I compiled this, no error occured. DMD version is DMD64 
> v2.065.(ldc2 exited with error function declaration without 
> return type)
>
> Why does this work? Or it is a bug?

You declared a variable template named "tuple" (with unused type 
parameters a, b) on that line.
http://dlang.org/template.html#variable-template

I think this is very confusable syntax...

void main()
{
     auto tuple(a, b) = foo2(1);

     writeln(tuple!(int, int)); // writes "Tuple!(int, bool)(1, 
true)"

     tuple!(int, int) = foo2(20);
     writeln(tuple!(int, int)); // writes "Tuple!(int, bool)(20, 
true)"

}