Problem with compilation( DMD compile run failed with exit code -6 )

[Akzwar via Digitalmars-d-learn]

We write new signal/slot system? like in QT.
https://github.com/dexset/descore/tree/de9ccae7a9907e5098f244a8683e42fb660d0b35/import/des/util/signal
https://github.com/dexset/descore/tree/de9ccae7a9907e5098f244a8683e42fb660d0b35/import/des/util/object

Unittests works fine, but after trying using it in our test 
application, we encountered a strange problem.
des/import/des/app/sdlevproc.d(57): Error: function 
des.util.signal.signal.Signal!(Vector!(2LU, int, "x 
y")).Signal.opCall (Vector!(2LU, int, "x y")) is not callable 
using argument types (MouseEvent)
But, one can pass to this method only mouse events, and event, 
that take Vector!(2LU, int, "x y") is in another class 
definition, and has another name. And there are few more errors 
like this.

Finally compilation crashes with exit code -6:
dmd: class.c:859: virtual void 
ClassDeclaration::semantic(Scope*): Assertion `type->ty != Tclass 
|| ((TypeClass *)type)->sym == this' failed.
FAIL 
.dub/build/application-debug-linux.posix-x86_64-dmd-9A2D5BEE385B6AEDFC08EE311E6172FC 
ftree executable

Test project:
https://github.com/deviator/fractaltree/tree/aea7ead22da7ffeaa55c9c74ef9e86b93bc60f8d

Does anyone has any suggestions about this issue?