Overhead for type conversions?

["Bobby D. Bryant" <bdbryant@mail.utexas.edu>]

Given these declarations -

   type f1 is new float;
   type f2 is new float;

   function "*"( left : in f1; right : in f2 ) return f1 is
   begin
      return( left * f1( right ) );
   end "*";

and given that run-time range checks are enabled, should I expect my
compiler to execute range checking code for each f1*f2 multiplication,
or will the compiler conclude from the definitions that the two types
are always convertible without error regardless of the specific value,
and thus not generate any code for a range check?

(In practice the compiler is GNAT.)

Thanks,
-- 
Bobby Bryant
Austin, Texas