VTAT, chapter 12 (Types), page 214

     An anchored type of the form `like anchor' appearing
     in a class `C' is valid  if  and  only if one of the
     following holds:

        1 `anchor' is the final name of  an  attribute  or
          function  of  `C', whose declared type is a non-
          Anchored reference type.

        2 The type appears in the text of a routine `r' of
          `C',  and  `anchor' is a formal argument of `r',
          whose declared type is a non-Anchored  reference
          type.

        3 `anchor' is the reserved word `Current'.