!ASIS Issue #092
!topic  Unwinding types for Corresponding_Expression_Type
!reference  ASIS 95-17.1
!from  Sergey Rybin
!keywords  types subtypes unwinding Corresponding_Expression_Type
!discussion

1. What does "unwinding subtypes" mean here?  Suppose we have:

      type Int is range -10_000 .. 10_000
      subtype Sub_Int is Int range -10 .. 10;
      Var : Sub_Int;

   What should be returned as Corresponding_Expression_Type for Sub_Int -
   the Element representing the declaration of type Int (but this would look
   like unwinding subtypes) or the declaration of subtype Sub_Int
   (this would look more logical and useful for applications, but this
   would contradict "Returns the type_declaration for the type of the
                                 ^^^^^^^^^^^^^^^^
   expression"

2. What does unwinding derived types mean here?
                       ^^^^^^^
   If you unwind _derived_ types (opposite to unwinding subtypes), you
   change the type.

!resolution  Accept
!date 98-03-26
!Notes

To be more precise, replace the following in Clause 17.1 from:

-- Returns the type_declaration for the type of the expression. This query
-- does not "unwind" subtypes or derived types to get to the
-- Corresponding_First_Subtype or Corresponding_Parent_Subtype declarations.

to:

-- Returns the type declaration for the type or subtype of the expression.
-- This query does not "unwind" subtypes or derived types to get to the
-- Corresponding_First_Subtype or Corresponding_Parent_Subtype declarations.
-- For example, for the following program text:
--
--     type Int is range -5_000 .. 5_000;
--     type My_Int is new Int;
--     type Good_Int is new My_Int;
--     Var: Good_Int;
--
-- The type declaration for Good_Int should be returned. The "unwinding" should
-- not occur. The type declaration for either My_Int or Int should not be returned.