COBCH1608 Illegal USAGE in this context

Certain USAGE types cannot be used in the procedure division header. For example:

class-id myClass1.
      
indexer-id string.
procedure division using i1 as COMP-3. *> this is incorrect
    getter.
    set property-value to i1.
end indexer.
end class.

class-id myClass2.
indexer-id string.
procedure division using i2 as binary-double. *> this is correct
    getter.
    set property-value to i2
end indexer.
end class.