[Issue 12540] New: Algebraic recursive alias declaration when a class contains an Algebraic member that can accept itself

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=12540

           Summary: Algebraic recursive alias declaration when a class
                    contains an Algebraic member that can accept itself
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: tcdknutson at gmail.com


--- Comment #0 from Dylan Knutson <tcdknutson at gmail.com> 2014-04-07 12:03:58 PDT ---
It's not possible to create an Algebraic alias which can take a class, where
that class has the same algebraic type as a member. 

Example code:
```
import std.variant;

alias SomeAlg = Algebraic!SomeClass;

class SomeClass {
  SomeAlg entity;
}

void main() {}
```

Yielding the error:
```
/d519/f212.d(3): Error: alias f212.SomeAlg recursive alias declaration
/opt/compilers/dmd2/include/std/variant.d(1227): Error: template instance
std.variant.maxSize!(SomeClass) error instantiating
/d519/f212.d(3):        instantiated from here: Algebraic!(SomeClass)
/d519/f212.d(3): Error: template instance std.variant.Algebraic!(SomeClass)
error instantiating
```


What's perhaps stranger is that this code does work:
```
import std.variant;

//alias SomeAlg = Algebraic!SomeClass;

class SomeClass {
  Algebraic!SomeClass entity;
}

void main() {}
```

But it's doing, as far as I can tell, the exact same thing.

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