Incorrect ambiguous name error

[mantkiew]

abstract FunctionalArchitecture
abstract Deployment
   abstract fa -> FunctionalArchitecture

// then we write our generic power window deployment

abstract PowerWindowFAA : FunctionalArchitecture
abstract PowerWindowDpl : Deployment
   abstract fa : fa -> PowerWindowFAA

// Finally, we want to specialize it to driver power window.
// Here we have concrete architecture

System
    DriverPowerWindowFAA : PowerWindowFAA       
    DriverPowerWindowDpl : PowerWindowDpl
       // refine the type again to driver
       fa : fa -> DriverPowerWindowFAA  

Results in an incorrect error:

Compile error at line 9 column 18...
clafer "fa" cannot be defined because the name should be unique in the same namespace.
Available paths:
c0_fa
c1_fa

The clafer c1_fa should not be taken into consideration because a clafer cannot extend itself.