[sv-ec] 6.24.1 static cast after mantis 1384 fix

There is bunch of inconsitency and unclerance after mantis  1384 fix

LRM draft 6 :

6.24.1 Description of    static cast: "If the expression is assignment
compatible with the casting type, then the cast shall return the value that
a variable of the casting type would hold after being assigned the
expression. If the expression is not assignment compatible with the casting
type, then if the casting type is an enumerated type, the behavior shall be
as described as in 6.19.4, and if the casting type is a bit-stream type, the
behavior shall be as described in 6.24.3."

The sentence is still open - what should happened if dest and source is not
assignment compatybile and casting type is not an enum not bit-stream type -
is it possible? What about classes - are they bit stream - is not so obvious

6.24.3: "An associative array type or class shall be illegal as a
destination type." (this was allowed in 1800-2005 now draft 6 bans it) 

Both above are contradictory - becaue 1st allows to cast to a type which is
assignment compatybile (which is possible for class handles - ie cast to
super class) while 2nd forbids static cast to  class type. IMHO there are
two solutions :

    - cast to class should be fdisallowed in all cases - sentence from
6.24.3 should be moved to 6.24.1

    - cast between class handles should be allowed - it should not perform
any kind of check on compile/elab time - but on run time it should triggger
fatal errors if casted types are not compatybile - this should be described
in 6.24.3. Cast where source is a non-class bit stream class and dectination
is a class handle should be forbidden in 6.24.3

as an addition an example - what should be the behaviour of tool in below
example

class B;
    reg x;
    function f(); 
        $display("B",x);
    endfunction
endclass

 
class A extends B;
    int y;
    function f(); 
        $display("B",y);
    endfunctionendclass
 
module top;
    A a;
    B b;
 
    initial begin
        b = 'B(a);        /// should it be legal?? this is ok according to
6.24.1 but offends 6.24.3
        a = 'A(b);        /// should it be legal?? this offends both :
6.24.1 and 6.24.3
         'B(a).f();        /// should it be legal?? this show the only
sensible usage of casting to base class type but is this ok according  to
syntax???
    end
endmodule

DANiel


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