Multiple constraints

Description

New multiple constraints for generic parameters

With the new ECMA standard for Eiffel multiple constraints for generic parameters were introduced.

class GENERIC_CLASS [G -> {B, C }]
 
feature
   f: G
 
   example is
         -- issue
      do
            -- Qualified feature call
         f.a
      end
 
end

The semantic given to the code above is, that an actual parameter passed for G must be conform to both classes: B and C.

The standard defines in section 8.12.23 what the basic type of such a multiple constraint formal generic is. However, this definition can only be used to clearly define the set of available features to G and not the semantic of a qualified feature call like f.a.