"alias" problem in fixed_pkg

sir, i am using fixed_pkg_c.vhd.during synthesis it gives error on alias statement.if i remove this "alias " only, it gives error

".

ERROR:HDLParsers:164 - Line 1024. parse error, unexpected IDENTIFIER"

the program copy where it gives the error is "function to_slv (

arg : UNRESOLVED_ufixed) -- fixed point vector

return STD_LOGIC_VECTOR;

to_StdLogicVector is to_slv [UNRESOLVED_ufixed

return STD_LOGIC_VECTOR];

to_Std_Logic_Vector is to_slv [UNRESOLVED_ufixed

return STD_LOGIC_VECTOR];

-- plz sir help me.............:cry: