------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                             S E M _ A G G R                              --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--                            $Revision: 1.161 $                            --
--                                                                          --
--   Copyright (C) 1992,1993,1994,1995,1996 Free Software Foundation, Inc.  --
--                                                                          --
-- GNAT is free software;  you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
-- MA 02111-1307, USA.                                                      --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
--                                                                          --
------------------------------------------------------------------------------

with Atree;    use Atree;
with Checks;   use Checks;
with Einfo;    use Einfo;
with Elists;   use Elists;
with Errout;   use Errout;
with Expander; use Expander;
with Exp_Util; use Exp_Util;
with Features; use Features;
with Freeze;   use Freeze;
with Hostparm;
with Itypes;   use Itypes;
with Namet;    use Namet;
with Nmake;    use Nmake;
with Nlists;   use Nlists;
with Opt;      use Opt;
with Rtsfind;  use Rtsfind;
with Sem;      use Sem;
with Sem_Case; use Sem_Case;
with Sem_Ch3;  use Sem_Ch3;
with Sem_Eval; use Sem_Eval;
with Sem_Res;  use Sem_Res;
with Sem_Util; use Sem_Util;
with Sem_Type; use Sem_Type;
with Sinfo;    use Sinfo;
with Snames;   use Snames;
with Stringt;  use Stringt;
with Stand;    use Stand;
with Tbuild;   use Tbuild;
with Uintp;    use Uintp;

package body Sem_Aggr is

   ----------------
   -- BEGIN JUNK --
   ----------------

   --  ??? THIS IS VERY TEMPORARY STUFF THAT WILL SOON BE GONE.
   --  IT"S A REMNENT OF the speck of sem_ch5 (Franco).

   type Case_Bounds is record
     Choice_Lo   : Node_Id;
     Choice_Hi   : Node_Id;
     Choice_Node : Node_Id;
   end record;

   type Case_Table_Type is array (Nat range <>) of Case_Bounds;
   --  Table type used by Check_Case_Choices procedure

   procedure Sort_Case_Table (Case_Table : in out Case_Table_Type);
   --  Sort the Case Table using the Lower Bound of each Choice as the key.
   --  A simple insertion sort is used since the number of choices in a case
   --  statement of variant part will usually be small and probably in near
   --  sorted order.

   ---------------------
   -- Sort_Case_Table --
   ---------------------

   procedure Sort_Case_Table (Case_Table : in out Case_Table_Type) is
      L : Int := Case_Table'First;
      U : Int := Case_Table'Last;
      K : Int;
      J : Int;
      T : Case_Bounds;

   begin
      K := L;

      while K /= U loop
         T := Case_Table (K + 1);
         J := K + 1;

         while J /= L
           and then Expr_Value (Case_Table (J - 1).Choice_Lo) >
                    Expr_Value (T.Choice_Lo)
         loop
            Case_Table (J) := Case_Table (J - 1);
            J := J - 1;
         end loop;

         Case_Table (J) := T;
         K := K + 1;
      end loop;
   end Sort_Case_Table;

   --------------
   -- END JUNK --
   --------------

   ------------------------------------------------------
   -- Subprograms used for RECORD AGGREGATE Processing --
   ------------------------------------------------------

   procedure Resolve_Record_Aggregate (N : Node_Id; Typ : Entity_Id);
   --  This procedure performs all the semantic checks required for record
   --  aggregates. Note that for aggregates analysis and resolution go
   --  hand in hand. Aggregate analysis has been delayed up to here and
   --  it is done while resolving the aggregate.
   --
   --    N is the N_Aggregate node.
   --    Typ is the record type for the aggregate resolution
   --
   --  While performing the semantic checks, this procedure
   --  builds a new Component_Association_List where each record field
   --  appears alone in a Component_Choice_List along with its corresponding
   --  expression. The record fields in the Component_Association_List
   --  appear in the same order in which they appear in the record type Typ.
   --
   --  Once this new Component_Association_List is built and all the
   --  semantic checks performed, the original aggregate subtree is replaced
   --  with the new named record aggregate just built. Note that the subtree
   --  substitution is performed with Rewrite_Substitute_Tree so as to be
   --  able to retrieve the original aggregate.
   --
   --  The aggregate subtree manipulation performed by Resolve_Record_Aggregate
   --  yields the aggregate format expected by Gigi. Typically, this kind of
   --  tree manipulations are done in the expander. However, because the
   --  semantic checks that need to be performed on record aggregates really
   --  go hand in hand with the record aggreagate normalization, the aggregate
   --  subtree transformation is performed during resolution rather than
   --  expansion. Had we decided otherwise we would have had to duplicate
   --  most of the code in the expansion procedure Expand_Record_Aggregate.
   --  Note, however, that all the expansion concerning aggegates for tagged
   --  records is done in Expand_Record_Aggregate.
   --
   --  The algorithm of Resolve_Record_Aggregate proceeds as follows:
   --
   --  1. Make sure that the record type against which the record aggregate
   --     has to be resolved is not abstract. Furthermore if the type is
   --     a null aggregate make sure the input aggregate N is also null.
   --
   --  2. Verify that the structure of the aggregate is that of a record
   --     aggregate. Specifically, look for component associations and ensure
   --     that each choice list only has identifiers or the N_Others_Choice
   --     node. Also make sure that if present, the N_Others_Choice occurs
   --     last and by itself.
   --
   --  3. If Typ contains discriminants, the values for each discriminant
   --     is looked for. If the record type Typ has variants, we check
   --     that the expressions corresponding to each discriminant ruling
   --     the (possibly nested) variant parts of Typ, are static. This
   --     allows us to determine the variant parts to which the rest of
   --     the aggregate must conform. The names of discriminants with their
   --     values are saved in a new association list, New_Assoc_List which
   --     is later augmented with the names and values of the remaining
   --     components in the record type.
   --
   --     During this phase we also make sure that every discriminant is
   --     assigned exactly one value. Note that when several values
   --     for a given discriminant are found, semantic processing continues
   --     looking for further errors. In this case it's the first
   --     discriminant value found which we will be recorded.
   --
   --     IMPORTANT NOTE: For derived tagged types this procedure expects
   --     First_Discriminant and Next_Discriminant to give the correct list
   --     of discriminants, in the correct order.
   --
   --  4. After all the discriminant values have been gathered, we can
   --     set the Etype of the record aggregate. If Typ contains no
   --     discriminants this is straightforward: the Etype of N is just
   --     Typ, otherwise a new implicit constrained subtype of Typ is
   --     built to be the Etype of N.
   --
   --  5. Gather the remaining record components according to the discriminant
   --     values. This involves recursively traversing the record type
   --     structure to see what variants are selected by the given discriminant
   --     values. This processing is a little more convoluted if Typ is a
   --     derived tagged types since we need to retrieve the record structure
   --     of all the ancestors of Typ.
   --
   --  6. After gathering the record components we look for their values
   --     in the record aggregate and emit appropriate error messages
   --     should we not find such values or should they be duplicated.
   --
   --  7. We then make sure no illegal component names appear in the
   --     record aggegate and make sure that the type of the record
   --     components appearing in a same choice list is the same.
   --     Finally we ensure that the others choice, if present, is
   --     used to provide the value of at least a record component.
   --
   --  8. The original aggregate node is replaced with the new named
   --     aggregate built in steps 3 through 6, as explained earlier.
   --
   --  Given the complexity of record aggregate resolution, the primary
   --  goal of this routine is clarity and simplicity rather than execution
   --  and storage efficiency. If there are only positional components in the
   --  aggregate the running time is linear. If there are associations
   --  the running time is still linear as long as the order of the
   --  associations is not too far off the order of the components in the
   --  record type. If this is not the case the running time is at worst
   --  quadratic in the size of the association list.

   procedure Gather_Components
     (Typ           : Entity_Id;
      Comp_List     : Node_Id;
      Governed_By   : List_Id;
      Into          : Elist_Id;
      Report_Errors : out Boolean);
   --  The purpose of this procedure is to gather the valid components
   --  in a record type according to the values of its discriminants.
   --  Specifically:
   --
   --    Typ is the type of the aggregate when its constrained discriminants
   --      need to be collected, otherwise it is Empty.
   --
   --    Comp_List is an N_Component_List node.
   --
   --    Governed_By is a list of N_Component_Association nodes,
   --     where each choice list contains the name of a discriminant and
   --     the expression field gives its value. The values of the
   --     discriminants governing the (possibly nested) variant parts in
   --     Comp_List are found in this Component_Association List.
   --
   --    Into is the list where the valid components are appended.
   --     Note that Into need not be an Empty list. If it's not, components
   --     are attached to its tail.
   --
   --    Report_Errors is set to True if the values of the discriminants
   --     are non-static.

   -----------------------------------------------------
   -- Subprograms used for ARRAY AGGREGATE Processing --
   -----------------------------------------------------

   function Resolve_Array_Aggregate
     (N              : Node_Id;
      Index          : Node_Id;
      Index_Constr   : Node_Id;
      Component_Typ  : Entity_Id;
      Others_Allowed : Boolean)
      return           Boolean;
   --  This procedure performs the semantic checks for an array aggregate.
   --  True is returned if the aggregate resolution succeeds.
   --  The procedure works by recursively checking each nested aggregate.
   --  Specifically, after checking a sub-aggreate nested at the i-th level
   --  we recursively check all the subaggregates at the i+1-st level (if any).
   --  Note that for aggregates analysis and resolution go hand in hand.
   --  Aggregate analysis has been delayed up to here and it is done while
   --  resolving the aggregate.
   --
   --    N is the current N_Aggregate node to be checked.
   --
   --    Index is the index node corresponding to the array sub-aggregate that
   --    we are currently checking (RM 4.3.3 (8)). Its Etype is the
   --    corresponding index type (or subtype).
   --
   --    Index_Constr is the node giving the applicable index constraint if
   --    any (RM 4.3.3 (10)).  It "is a constraint provided by certain
   --    contexts [...] that can be used to determine the bounds of the array
   --    value specified by the aggregate". If Others_Allowed below is False
   --    there is no applicable index constraint and this node is set to Index.
   --
   --    Component_Typ is the array component type.
   --
   --    Others_Allowed indicates whether an others choice is allowed
   --    in the context where the top-level aggregate appeared.
   --
   --  The algorithm of Resolve_Array_Aggregate proceeds as follows:
   --
   --  1. Make sure that the others choice, if present, is by itself and
   --     appears last in the sub-aggregate. Check that we do not have
   --     positional and named components in the array sub-aggregate (unless
   --     the named association is an others choice). Finally if an others
   --     choice is present, make sure it is allowed in the aggregate contex.
   --
   --  2. If the array sub-aggregate contains discrete_choices:
   --
   --     (A) Verify their validity. Specifically verify that:
   --
   --        (a) If a null range is present it must be the only possible
   --            choice in the array aggregate.
   --
   --        (b) Ditto for a non static range.
   --
   --        (c) Ditto for a non static expression.
   --
   --        In addition this step analyzes and resolves each discrete_choice,
   --        making sure that its type is the type of the corresponding Index.
   --        If we are not at the lowest array aggregate level (in the case of
   --        multi-dimensional aggregates) then invoke Resolve_Array_Aggregate
   --        recursively on each component expression. Otherwise, resolve
   --        the bottom level component expressions against the expected
   --        component type ONLY IF the component type is scalar or it
   --        corresponds to a single discrete choice which is not an others
   --        choice (to see why read the DELAYED COMPONENT RESOLUTION below).
   --
   --     (B) Determine the bounds of the sub-aggregate and lowest and
   --         highest choice values.
   --
   --  3. For positional aggregates:
   --
   --     (A) Loop over the component expressions either recursively invoking
   --         Resolve_Array_Aggregate on each of these for multi-dimensional
   --         array aggregates or resolving the bottom level component
   --         expressions against the expected component type.
   --
   --     (B) Determine the bounds of the positional sub-aggregates.
   --
   --  4. Try to determine statically whether the evaluation of the array
   --     sub-aggregate raises Constraint_Error. If yes emit proper
   --     warnings. The precise checks are the following:
   --
   --     (A) Check that the index range defined by aggregate bounds is
   --         compatible with corresponding index subtype.
   --         We also check against the base type. In fact it could be that
   --         Low/High bounds of the base type are static whereas those of
   --         the index subtype are not. Thus if we can statically catch
   --         a problem with respect to the base type we are guaranteed
   --         that the same problem will arise with the index subtype
   --
   --     (B) If we are dealing with a named aggregate containing an others
   --         choice and at least one discrete choice then make sure the range
   --         specified by the discrete choices does not overflow the
   --         aggregate bounds. We also check against the index type and base
   --         type bounds for the same reasons given in (A).
   --
   --     (C) If we are dealing with a positional aggregate with an others
   --         choice make sure the number of positional elements specified
   --         does not overflow the aggregate bounds. We also check against
   --         the index type and base type bounds as mentioned in (A).
   --
   --     Finally construct an N_Range node giving the sub-aggregate bounds.
   --     Set the Aggregate_Bounds field of the sub-aggregate to be this
   --     N_Range. The routine Array_Aggr_Subtype below uses such N_Ranges
   --     to build the appropriate aggregate subtype. Aggregate_Bounds
   --     information is needed during expansion.
   --
   --  DELAYED COMPONENT RESOLUTION: The resolution of bottom level component
   --  expressions in an array aggregate may call Duplicate_Subexpr or some
   --  other routine that inserts code just outside the outermost aggregate.
   --  If the array aggregate contains discrete choices or an others choice,
   --  this may be wrong. Consider for instance the following example.
   --
   --    type Rec is record
   --       V : Integer := 0;
   --    end record;
   --
   --    type Acc_Rec is access Rec;
   --    Arr : array (1..3) of Acc_Rec := (1 .. 3 => new Rec);
   --
   --  Then the transformation of "new Rec" that occurs during resolution
   --  entails the following code modifications
   --
   --    P7b : constant Acc_Rec := new Rec;
   --    Rec_init_proc (P7b.all);
   --    Arr : array (1..3) of Acc_Rec := (1 .. 3 => P7b);
   --
   --  This code transformation is clearly wrong, since we need to call
   --  "new Rec" for each of the 3 array elements. To avoid this problem we
   --  delay resolution of the components of non positional array aggregates
   --  to the expansion phase. As an optimization, if the discrete choice
   --  specifies a single value we do not delay resolution.

   function Array_Aggr_Subtype (N : Node_Id; Typ : Node_Id) return Entity_Id;
   --  This routine returns the type or subtype of an array aggregate.
   --
   --    N is the array aggregate node whose type we return.
   --
   --    Typ is the context type in which N occurs.
   --
   --  This routine creates an implicit array subtype whose bouds are
   --  those defined by the aggregate. When this routine is invoked
   --  Resolve_Array_Aggregate has already processed aggregate N. Thus the
   --  Aggregate_Bounds of each sub-aggregate, is an N_Range node giving the
   --  sub-aggregate bounds. When building the aggegate itype, this function
   --  traverses the array aggregate N collecting such Aggregate_Bounds and
   --  constructs the proper array aggregate itype.
   --
   --  Note that in the case of multidimensional aggregates each inner
   --  sub-aggregate corresponding to a given array dimension, may provide a
   --  different bounds. If it is possible to determine statically that
   --  some sub-aggregates corresponding to the same index do not have the
   --  same bounds, then a warning is emitted. If such check is not possible
   --  statically (because some sub-aggregate bounds are dynamic expressions)
   --  then this job is left to the expander. In all cases the particular
   --  bounds that this function will chose for a given dimension is the first
   --  N_Range node for a sub-aggregate corresponding to that dimension.
   --
   --  Note that the Raises_Constraint_Error flag of an array aggregate
   --  whose evaluation is determined to raise CE by Resolve_Array_Aggregate,
   --  is set in Resolve_Array_Aggregate but the aggregate is not
   --  immediately replaced with a raise CE. In fact, Array_Aggr_Subtype must
   --  first construct the proper itype for the aggregate (Gigi needs
   --  this). After constructing the proper itype we will eventually  replace
   --  the top-level aggregate with a raise CE (done in Resolve_Aggregate).
   --  Of course in cases such as:
   --
   --     type Arr is array (integer range <>) of Integer;
   --     A : Arr := (positive range -1 .. 2 => 0);
   --
   --  The bounds of the aggregate itype are cooked up to look reasonable
   --  (in this particular case the bounds will be 1 .. 2).

   procedure Constraint_Check (Exp : Node_Id; Check_Typ : Entity_Id);
   --  Checks expression Exp against subtype Check_Typ. If Exp is an
   --  aggregate and Check_Typ a constrained record type with discriminants,
   --  we generate the appropriate discriminant checks. If Exp is an array
   --  aggregate then emit the appropriate length checks. If Exp is a scalar
   --  type, or a string literal, Exp is changed into Check_Typ'(Exp) to
   --  ensure that range checks are performed at run time.

   procedure Make_String_Into_Aggregate (N : Node_Id);
   --  A string literal can appear in  a context in  which a one dimensional
   --  array of characters is expected. This procedure simply rewrites the
   --  string as an aggregate, prior to resolution.

   -----------------------
   -- Resolve_Aggregate --
   -----------------------

   procedure Resolve_Aggregate (N : Node_Id; Typ : Entity_Id) is
      Pkind : constant Node_Kind := Nkind (Parent (N));

      Aggr_Subtyp : Entity_Id;
      --  The actual aggregate subtype. This is not necessarily the same as Typ
      --  which is the subtype of the context in which the aggregate was found.

   begin
      if Is_Limited_Type (Typ) then
         Error_Msg_N ("aggregate type cannot be limited", N);

      elsif Is_Limited_Composite (Typ) then
         Error_Msg_N ("aggregate type cannot have limited component", N);

      elsif Is_Class_Wide_Type (Typ) then
         Error_Msg_N ("aggregate not available for limited array", N);

      elsif Typ = Any_String
        or else Typ = Any_Composite
      then
         Error_Msg_N ("no unique type for aggregate", N);
         Set_Etype (N, Any_Composite);

      elsif Is_Array_Type (Typ) and then Null_Record_Present (N) then
         Error_Msg_N ("null record forbidden in array aggregate", N);

      elsif Is_Record_Type (Typ) then
         Resolve_Record_Aggregate (N, Typ);

      elsif Is_Array_Type (Typ) then

         --  First a special test, for the case of a positional aggregate
         --  of characters which can be replaced by a string literal.

         if Number_Dimensions (Typ) = 1
           and then
             (Root_Type (Component_Type (Typ)) = Standard_Character
               or else
              Root_Type (Component_Type (Typ)) = Standard_Wide_Character)
           and then No (Component_Associations (N))
           and then not Is_Limited_Composite (Typ)
           and then not Is_Private_Composite (Typ)
           and then not Is_Bit_Packed_Array (Typ)
         then
            declare
               Expr : Node_Id;

            begin
               Expr := First (Expressions (N));
               while Present (Expr) loop
                  exit when Nkind (Expr) /= N_Character_Literal;
                  Expr := Next (Expr);
               end loop;

               if No (Expr) then
                  Start_String;

                  Expr := First (Expressions (N));
                  while Present (Expr) loop
                     Store_String_Char (Char_Literal_Value (Expr));
                     Expr := Next (Expr);
                  end loop;

                  Rewrite_Substitute_Tree (N,
                    Make_String_Literal (Sloc (N), End_String));

                  Analyze_And_Resolve (N, Typ);
                  return;
               end if;
            end;
         end if;

         --  Here if we have a real aggregate to deal with

         Array_Aggregate : declare
            Aggr_Resolved : Boolean;
            Aggr_Typ      : Entity_Id := Etype (Typ);
            --  This is the unconstrained array type, which is the type
            --  against which the aggregate is to be resoved. Typ itself
            --  is the array type of the context which may not be the same
            --  subtype as the subtype for the final aggregate.

         begin
            --  In the following we determine whether an others choice is
            --  allowed inside the array aggregate. The test checks the context
            --  in which the array aggregate occurs. If the context does not
            --  permit it, or the aggregate type is unconstrained, an others
            --  choice is not allowed.
            --
            --  Note that there is no node for Explicit_Actual_Parameter.
            --  To test for this context we therefore have to test for node
            --  N_Parameter_Association which itself appears only if there is a
            --  formal parameter. Consequently we also need to test for
            --  N_Procedure_Call_Statement or N_Function_Call.

            if Is_Constrained (Typ) and then
              (Pkind = N_Assignment_Statement      or else
               Pkind = N_Parameter_Association     or else
               Pkind = N_Function_Call             or else
               Pkind = N_Procedure_Call_Statement  or else
               Pkind = N_Generic_Association       or else
               Pkind = N_Formal_Object_Declaration or else
               Pkind = N_Return_Statement          or else
               Pkind = N_Object_Declaration        or else
               Pkind = N_Component_Declaration     or else
               Pkind = N_Parameter_Specification   or else
               Pkind = N_Qualified_Expression      or else
               Pkind = N_Aggregate                 or else
               Pkind = N_Component_Association)
            then
               Aggr_Resolved :=
                 Resolve_Array_Aggregate
                   (N,
                    Index          => First_Index (Aggr_Typ),
                    Index_Constr   => First_Index (Typ),
                    Component_Typ  => Component_Type (Typ),
                    Others_Allowed => True);

            else
               Aggr_Resolved :=
                 Resolve_Array_Aggregate
                   (N,
                    Index          => First_Index (Aggr_Typ),
                    Index_Constr   => First_Index (Aggr_Typ),
                    Component_Typ  => Component_Type (Typ),
                    Others_Allowed => False);
            end if;

            if not Aggr_Resolved then
               Aggr_Subtyp := Any_Composite;
            else
               Aggr_Subtyp := Array_Aggr_Subtype (N, Typ);
            end if;

            Set_Etype (N, Aggr_Subtyp);
         end Array_Aggregate;

      else
         Error_Msg_N ("illegal context for aggregate", N);

      end if;

      --  If we can determine statically that the evaluation of the
      --  aggregate raises Constraint_Error, then replace the
      --  aggregate with an N_Raise_Constraint_Error node, but set the
      --  Etype to the right aggregate subtype. Gigi needs this.

      if Raises_Constraint_Error (N) then
         Aggr_Subtyp := Etype (N);
         Rewrite_Substitute_Tree (N, Make_Raise_Constraint_Error (Sloc (N)));
         Set_Raises_Constraint_Error (N);
         Set_Etype (N, Aggr_Subtyp);
         Set_Analyzed (N);
      end if;

   end Resolve_Aggregate;

   ---------------------------------
   -- Resolve_Extension_Aggregate --
   ---------------------------------

   --  There are two cases to consider:

   --  a) If the ancestor part is a type mark, the components needed are
   --  the difference between the components of the expected type and the
   --  components of the given type mark.

   --  b) If the ancestor part is an expression, it must be unambiguous,
   --  and once we have its type we can also compute the needed  components
   --  as in the previous case. In both cases, if the ancestor type is not
   --  the immediate ancestor, we have to build this ancestor recursively.

   --  In both cases discriminants of the ancestor type do not play a
   --  role in the resolution of the needed components, because inherited
   --  discriminants cannot be used in a type extension. As a result we can
   --  compute independently the list of components of the ancestor type and
   --  of the expected type.

   procedure Resolve_Extension_Aggregate (N : Node_Id; Typ : Entity_Id) is
      A        : constant Node_Id := Ancestor_Part (N);
      A_Type   : Entity_Id;
      I        : Interp_Index;
      It       : Interp;
      Imm_Type : Entity_Id;

      function Valid_Ancestor_Type return Boolean;
      --  Verify that the type of the ancestor part is a non-private ancestor
      --  of the expected type.

      function Valid_Ancestor_Type return Boolean is
         Imm_Type : Entity_Id;

      begin
         Imm_Type := Base_Type (Typ);
         while Is_Derived_Type (Imm_Type)
           and then Etype (Imm_Type) /= Base_Type (A_Type)
         loop
            Imm_Type := Etype (Base_Type (Imm_Type));
         end loop;

         if Etype (Imm_Type) /= Base_Type (A_Type) then
            Error_Msg_NE ("expect ancestor type of &", A, Typ);
            return False;
         else
            return True;
         end if;
      end Valid_Ancestor_Type;

   --  Start of processing for Resolve_Extension_Aggregate

   begin
      Analyze (A);

      if not Is_Tagged_Type (Typ) then
         Error_Msg_N ("type of extension aggregate must be tagged", N);
         return;

      elsif Is_Limited_Type (Typ) then
         Error_Msg_N ("aggregate type cannot be limited", N);
         return;

      elsif Is_Class_Wide_Type (Typ) then
         Error_Msg_N ("aggregate cannot be of a class-wide type", N);
         return;
      end if;

      if Is_Entity_Name (A)
        and then Is_Type (Entity (A))
      then
         A_Type   := Entity (A);
         Imm_Type := Base_Type (Typ);

         if Valid_Ancestor_Type then
            Resolve_Record_Aggregate (N, Typ);
         end if;

      elsif Nkind (A) /= N_Aggregate then
         if Is_Overloaded (A) then
            A_Type := Any_Type;
            Get_First_Interp (A, I, It);

            while Present (It.Typ) loop

               if Is_Tagged_Type (It.Typ)
                  and then not Is_Limited_Type (It.Typ)
               then
                  if A_Type /= Any_Type then
                     Error_Msg_N ("cannot resolve expression", A);
                     return;
                  else
                     A_Type := It.Typ;
                  end if;
               end if;

               Get_Next_Interp (I, It);
            end loop;

            if A_Type = Any_Type then
               Error_Msg_N
                 ("ancestor part must be non-limited tagged type", A);
               return;
            end if;

         else
            A_Type := Etype (A);
         end if;

         if Valid_Ancestor_Type then
            Resolve (A, A_Type);
            Check_Non_Static_Context (A);
            Resolve_Record_Aggregate (N, Typ);
         end if;

      else
         Error_Msg_N (" No unique type for this aggregate",  A);
      end if;

   end Resolve_Extension_Aggregate;

   ------------------------------
   -- Resolve_Record_Aggregate --
   ------------------------------

   procedure Resolve_Record_Aggregate (N : Node_Id; Typ : Entity_Id) is
      Regular_Aggr    : constant Boolean := Nkind (N) /= N_Extension_Aggregate;

      Constr_Itype    : Entity_Id;
      --  Constrained subtype, created if Typ has discriminants.

      New_Assoc_List  : List_Id := New_List;
      New_Assoc       : Node_Id;
      --  New_Assoc_List is the newly built list of N_Component_Association
      --  nodes. New_Assoc is one such N_Component_Association node in it.
      --  Please note that while Assoc and New_Assoc contain the same
      --  kind of nodes, they are used to iterate over two different
      --  N_Component_Association lists.

      Others_Etype : Entity_Id := Empty;
      --  This variable is used to save the Etype of the last record component
      --  that takes its value from the others choice. Its purpose is:
      --
      --    (a) make sure the others choice is useful
      --
      --    (b) make sure the type of all the components whose value is
      --        subsumed by the others choice are the same.
      --
      --  This variable is updated as a side effect of function Get_Value

      procedure Add_Association (Component : Entity_Id; Expr : Node_Id);
      --  Builds a new N_Component_Association node which associates
      --  Component to expression Expr and adds it to the new association
      --  list New_Assoc_List being built.

      function Discr_Present (Discr : Entity_Id) return Boolean;
      --  If aggregate N is a regular aggregate this routine will return True.
      --  Otherwise, if N is an extension aggreagte, Discr is a discriminant
      --  whose value may already have been specified by N's ancestor part,
      --  this routine checks whether this is indeed the case and if so
      --  returns False, signaling that no value for Discr should appear in the
      --  N's aggregate part. Also, in this case, the routine appends to
      --  New_Assoc_List Discr the discriminant value specified in the ancestor
      --  part.

      function Get_Value
        (Compon                 : Node_Id;
         From                   : List_Id;
         Consider_Others_Choice : Boolean := False)
         return                   Node_Id;
      --  Given a record component stored in parameter Compon, the
      --  following function returns its value as it appears in the list
      --  From, which is a list of N_Component_Association nodes. If no
      --  component association has a choice for the searched component,
      --  the value provided by the others choice is returned, if there
      --  is  one and Consider_Others_Choice is set to true. Otherwise
      --  Empty is returned. If there is more than one component association
      --  giving a value for the searched record component, an error message
      --  is emitted and the first found value is returned.
      --
      --  If Consider_Others_Choice is set and the returned expression comes
      --  from the others choice, then Others_Etype is set as a side effect.
      --  An error message is emitted if the components taking their value
      --  from the others choice do not have same type.

      function Replace_Discriminants (In_Type : Entity_Id) return Entity_Id;
      --  In_Type is a type or subtype. If In_Type is a record subtype or an
      --  array subtype, a new Itype is created and returned. This Itype is
      --  attached to the aggregate node N. It is a copy of In_Type except
      --  that every occurrence of a record discriminant of the original
      --  record aggregate type Typ is replaced with its corresponding value
      --  as given by the record aggregate.
      --
      --  Note that the Itype is created only if there is at least one such
      --  discriminant in subtype In_Type. Otherwise In_Type is returned.
      --  For example consider the following code:
      --
      --    type rec (D : integer) is record
      --       F : String (1..D);
      --    end record;
      --
      --    X : rec := (D => 3, "abc");
      --
      --  When analyzing the record aggregate, the Etype initially found for
      --  field F is String (1 .. D). However the Etype of "abc" must be
      --  String  (1..3). Replace_Discriminants carries out precisely this
      --  transformation, i.e. in this case
      --
      --    Replace_Discriminants (String (1..D))
      --
      --  returns
      --
      --    String (1..3).
      --
      --  Note that this function begins creating an Itype, before it knows
      --  whether it will be useful or not. If the Itype is not needed, that
      --  storage is wasted.

      procedure Resolve_Aggr_Expr (Expr : Node_Id; Component : Node_Id);
      --  Analyzes and resolves expression Expr against the Etype of the
      --  Component. This routine also applies all appropiate checks to Expr.
      --  It finally saves a Expr in the newly created association list that
      --  will be attached to the final record aggregate. Note that if the
      --  Parent pointer of Expr is not set then Expr was produced with a
      --  New_copy_Tree or some such.

      ---------------------
      -- Add_Association --
      ---------------------

      procedure Add_Association (Component : Entity_Id; Expr : Node_Id) is
         New_Assoc   : Node_Id;
         Choice_List : List_Id := New_List;

      begin
         Append (New_Occurrence_Of (Component, Sloc (Expr)), Choice_List);
         New_Assoc :=
           Make_Component_Association (Sloc (Expr),
             Choices    => Choice_List,
             Expression => Expr);
         Append (New_Assoc, New_Assoc_List);
      end Add_Association;

      -------------------
      -- Discr_Present --
      -------------------

      function Discr_Present (Discr : Entity_Id) return Boolean is
         Loc : Source_Ptr;

         Ancestor     : Node_Id;
         Discr_Expr   : Node_Id;

         Ancestor_Typ : Entity_Id;
         Orig_Discr   : Entity_Id;
         D            : Entity_Id;
         D_Val        : Elmt_Id;

         Ancestor_Is_Subtyp : Boolean;

      begin
         if Regular_Aggr then
            return True;
         end if;

         Ancestor     := Ancestor_Part (N);
         Ancestor_Typ := Etype (Ancestor);
         Loc          := Sloc (Ancestor);

         Ancestor_Is_Subtyp :=
           Is_Entity_Name (Ancestor) and then Is_Type (Entity (Ancestor));

         --  If the ancestor part has no discriminants clearly N's aggregate
         --  part must provide a value for Discr.

         if not Has_Discriminants (Ancestor_Typ) then
            return True;

         --  If the ancestor part is an unconstrained subtype mark then the
         --  Discr must be present in N's aggregate part.

         elsif Ancestor_Is_Subtyp
           and then not Is_Constrained (Entity (Ancestor))
         then
            return True;
         end if;

         --  Now look to see if Discr was specified in the ancestor part.

         Orig_Discr := Original_Record_Component (Discr);
         D          := First_Discriminant (Ancestor_Typ);

         if Ancestor_Is_Subtyp then
            D_Val := First_Elmt (Discriminant_Constraint (Entity (Ancestor)));
         end if;

         while Present (D) loop
            --  If Ancestor has already specified Disc value than
            --  insert its value in the final aggregate.

            if Original_Record_Component (D) = Orig_Discr then
               if Ancestor_Is_Subtyp then
                  Discr_Expr := New_Copy_Tree (Node (D_Val));
               else
                  Discr_Expr :=
                    Make_Selected_Component (Loc,
                      Prefix        => Duplicate_Subexpr (Ancestor),
                      Selector_Name => New_Occurrence_Of (Discr, Loc));
               end if;

               Resolve_Aggr_Expr (Discr_Expr, Discr);
               return False;
            end if;

            D := Next_Discriminant (D);

            if Ancestor_Is_Subtyp then
               D_Val := Next_Elmt (D_Val);
            end if;
         end loop;

         return True;
      end Discr_Present;

      ---------------
      -- Get_Value --
      ---------------

      function Get_Value
        (Compon                 : Node_Id;
         From                   : List_Id;
         Consider_Others_Choice : Boolean := False)
         return                   Node_Id
      is
         Assoc         : Node_Id;
         Expr          : Node_Id := Empty;
         Selector_Name : Node_Id;

      begin
         if Present (From) then
            Assoc := First (From);
         else
            return Empty;
         end if;

         while Present (Assoc) loop
            Selector_Name := First (Choices (Assoc));
            while Present (Selector_Name) loop
               if Nkind (Selector_Name) = N_Others_Choice then
                  if Consider_Others_Choice and then No (Expr) then
                     if Present (Others_Etype) and then
                        Base_Type (Others_Etype) /= Base_Type (Etype (Compon))
                     then
                        Error_Msg_N ("components in OTHERS choice must " &
                                     "have same type", Selector_Name);
                     end if;

                     Others_Etype := Etype (Compon);

                     --  We need to duplicate the expression for each
                     --  component involved in the others choice.

                     return New_Copy_Tree (Expression (Assoc));
                  end if;

               elsif Chars (Compon) = Chars (Selector_Name) then
                  if No (Expr) then
                     --  We need to duplicate the expression when several
                     --  components are grouped together with a "|" choice.
                     --  For instance "filed1 | filed2 => Expr"

                     if Present (Next (Selector_Name)) then
                        Expr := New_Copy_Tree (Expression (Assoc));
                     else
                        Expr := Expression (Assoc);
                     end if;

                  else
                     Error_Msg_NE
                       ("more than one value supplied for &",
                        Selector_Name, Compon);

                  end if;
               end if;

               Selector_Name := Next (Selector_Name);
            end loop;

            Assoc := Next (Assoc);
         end loop;

         return Expr;
      end Get_Value;

      ---------------------------
      -- Replace_Discriminants --
      ---------------------------

      function Replace_Discriminants (In_Type : Entity_Id) return Entity_Id is
         New_Expr_List      : Elist_Id;
         Discrim_Constraint : Elmt_Id;

         Base_Index     : Entity_Id;
         Index_Type     : Entity_Id;
         Old_Index      : Node_Id;
         New_Index      : Node_Id;
         New_Index_List : List_Id;

         Old_Expr  : Node_Id;
         New_Expr  : Node_Id;
         Low_Expr  : Node_Id;
         High_Expr : Node_Id;

         Itype  : Entity_Id;

         Must_Check_Range     : Boolean := False;
         Need_To_Create_Itype : Boolean := False;

         function Get_Discr_Value (Old_Expr : Node_Id) return Node_Id;
         --  Given a reference to a discriminant in N, returns the
         --  expression for its value.

         function Get_Discr_Value (Old_Expr : Node_Id) return Node_Id is
         begin
            return
              Duplicate_Subexpr (
                Get_Discriminant_Value (
                  Entity (Old_Expr),
                  Etype (Constr_Itype),
                  Discriminant_Constraint (Constr_Itype)));
         end Get_Discr_Value;

      --  Start of processing for Replace_Discriminants

      begin
         --  In the following code N refers to the input aggregate node and Typ
         --  its type. These are the parameters of Resolve_Record_Aggregate.

         if not Has_Discriminants (Typ)
           or else (Ekind (In_Type) /= E_Record_Subtype
                      and then
                    Ekind (In_Type) /= E_Array_Subtype)
         then
            return In_Type;
         end if;

         if Ekind (In_Type) = E_Record_Subtype and then
            Has_Discriminants (In_Type)
         then
            New_Expr_List := New_Elmt_List;

            Discrim_Constraint :=
              First_Elmt (Discriminant_Constraint (In_Type));

            while Present (Discrim_Constraint) loop
               Old_Expr := Node (Discrim_Constraint);

               if Nkind (Old_Expr)          = N_Identifier   and then
                  Ekind (Entity (Old_Expr)) = E_Discriminant
               then
                  Need_To_Create_Itype := True;
                  New_Expr := Get_Discr_Value (Old_Expr);
                  Append_Elmt (New_Expr, New_Expr_List);

               else
                  Append_Elmt (Old_Expr, New_Expr_List);
               end if;

               Discrim_Constraint := Next_Elmt (Discrim_Constraint);
            end loop;

            if not Need_To_Create_Itype then
               return In_Type;
            end if;

            Itype := Create_Itype (E_Record_Subtype, N);

            Set_Etype                    (Itype, Base_Type         (In_Type));
            Set_Size_Info                (Itype,                   (In_Type));
            Set_Is_Tagged_Type           (Itype, Is_Tagged_Type    (In_Type));
            Set_Has_Discriminants        (Itype);
            Set_Is_Constrained           (Itype);
            Set_First_Entity             (Itype, First_Entity      (In_Type));
            Set_Last_Entity              (Itype, Last_Entity       (In_Type));
            Set_Depends_On_Private       (Itype, Depends_On_Private
                                                                   (In_Type));
            Conditional_Delay            (Itype, In_Type);

            Set_Discriminant_Constraint  (Itype, New_Expr_List);
            Set_Girder_Constraint_From_Discriminant_Constraint (Itype);

            return Itype;

         elsif Ekind (In_Type) = E_Array_Subtype then
            New_Index_List := New_List;
            Set_Parent (New_Index_List, N);

            Old_Index        := First_Index (In_Type);
            Base_Index       := First_Index (Etype (In_Type));
            Must_Check_Range := False;

            while Present (Old_Index) loop
               New_Index := New_Copy_Tree (Old_Index);

               if Nkind (New_Index) = N_Range then
                  Set_Etype (New_Index, Base_Type (Etype (Old_Index)));

                  Get_Index_Bounds (New_Index, Low_Expr, High_Expr);

                  Old_Expr := Low_Expr;
                  for J in 1 .. 2 loop
                     if Nkind (Old_Expr)         = N_Identifier   and then
                       Ekind (Entity (Old_Expr)) = E_Discriminant
                     then
                        Need_To_Create_Itype := True;

                        New_Expr := Get_Discr_Value (Old_Expr);

                        --  The index type may have a constraint that is
                        --  tighter than that of the discriminant declaration.
                        --  Check is inserted below, after Itype is built.

                        if Etype (Old_Expr) /= Etype (Base_Index) then
                           Must_Check_Range := True;
                        end if;

                        if J = 1 then
                           Set_Low_Bound
                             (New_Index, New_Expr);
                        else
                           Set_High_Bound
                             (New_Index, New_Expr);
                        end if;
                     end if;

                     Old_Expr := High_Expr;
                  end loop;

                  --  Create anonymous index type for range.

                  Index_Type :=
                    Create_Itype (Subtype_Kind (Ekind (Etype (New_Index))), N);

                  Set_Etype (Index_Type, Etype (New_Index));

                  if Is_Character_Type (Etype (New_Index)) then
                     Set_Is_Character_Type (Index_Type, True);
                  end if;

                  Set_Size_Info        (Index_Type,       (Etype (New_Index)));
                  Set_First_Rep_Item   (Index_Type, First_Rep_Item
                                                          (Etype (New_Index)));
                  Set_Scalar_Range     (Index_Type, New_Index);

                  Set_Etype (New_Index, Index_Type);

                  if Must_Check_Range then
                     Set_Parent (New_Index, N);
                     Set_Has_Dynamic_Range_Check (New_Index, False);
                     Apply_Range_Check (New_Index, Etype (Base_Index));
                     Set_Parent (New_Index, Empty);
                  end if;
               end if;

               Append (New_Index, To => New_Index_List);
               Old_Index  := Next_Index (Old_Index);
               Base_Index := Next_Index (Base_Index);
            end loop;

            if not Need_To_Create_Itype then
               return In_Type;
            end if;

            Itype := Create_Itype (E_Array_Subtype, N);

            Set_Etype          (Itype, Base_Type                (In_Type));
            Set_Size_Info      (Itype,                          (In_Type));
            Set_Depends_On_Private
                               (Itype, Depends_On_Private       (In_Type));
            Set_Convention     (Itype, Convention               (In_Type));

            Set_Is_Constrained (Itype);
            Set_First_Index    (Itype, First (New_Index_List));
            Set_Component_Type (Itype,
                                  Replace_Discriminants
                                    (In_Type => Component_Type (In_Type)));

            --  The replacement above is useless, the component type cannot
            --  depend on discriminants. This is sufficient:

            --  Set_Component_Type (Itype, Component_Type (In_Type));

            --  ??? should more fields be set (see other place in Sem_Aggr
            --  where an array subtype is created ...)

            Conditional_Delay  (Itype, In_Type);
            return Itype;
         end if;

         return In_Type;
      end Replace_Discriminants;

      -----------------------
      -- Resolve_Aggr_Expr --
      -----------------------

      procedure Resolve_Aggr_Expr (Expr : Node_Id; Component : Node_Id) is
         New_C     : Entity_Id := Component;
         Expr_Type : Entity_Id := Empty;

         Relocate  : Boolean;
         --  Set to True if the resolved Expr node needs to be relocated
         --  when attached to the newly created association list. This node
         --  need not be relocated if its parent pointer is not set.
         --  In fact in this case Expr is the output of a New_Copy_Tree call.
         --  if Relocate is True then we have analyzed the expression node
         --  in the original aggregate and hence it needs to be relocated
         --  when moved over the new association list.

      begin
         --  When resolving an expression we have to make sure that
         --  the discriminants appearing in the type for the expression
         --  as they appear in the Etype of the component are replaced
         --  by the actual disciminant values that are contained in the
         --  record aggregate.

         if Ekind (Component) = E_Discriminant then
            Expr_Type := Etype (Component);

         --  For tagged types we have already build the correct fully
         --  constrained subtype for N. So do not use Replace_Discriminats
         --  which is buggy for tagged types (and possibly for unatgged types
         --  as well) just use the previously build constrained tagged subtype.

         elsif Is_Tagged_Type (Typ) then
            New_C := First_Component (Etype (N));
            while Present (New_C) loop
               if Chars (New_C) = Chars (Component) then
                  Expr_Type := Etype (New_C);
                  exit;
               end if;

               New_C := Next_Component (New_C);
            end loop;

            pragma Assert (Present (Expr_Type));

         else
            --  ??? Replace_Discriminants should really be eliminated.

            Expr_Type := Replace_Discriminants (Etype (Component));
         end if;

         --  If the Parent pointer of Expr is not set, Expr is an expression
         --  duplicated by New_Tree_Copy (this happens for record aggregates
         --  that look like (Field1 | Filed2 => Expr) or (others => Expr)).
         --  Such a duplicated expression must be attached to the tree
         --  before analysis and resolution to enforce the rule that a tree
         --  fragment should never be analyzed or resolved unless it is
         --  attached to the current compilation unit.

         if No (Parent (Expr)) then
            Set_Parent (Expr, N);
            Relocate := False;
         else
            Relocate := True;
         end if;

         Analyze_And_Resolve (Expr, Expr_Type);
         Constraint_Check (Expr, Expr_Type);

         if Raises_Constraint_Error (Expr) then
            Set_Raises_Constraint_Error (N);
         end if;

         if Relocate then
            Add_Association (New_C, Relocate_Node (Expr));
         else
            Add_Association (New_C, Expr);
         end if;

      end Resolve_Aggr_Expr;

      --  Resolve_Record_Aggregate local variables

      Assoc : Node_Id;
      --  N_Component_Association node belonging to the input aggregate N

      Expr            : Node_Id;
      Positional_Expr : Node_Id;

      Component      : Entity_Id;
      Component_Elmt : Elmt_Id;
      Components     : Elist_Id := New_Elmt_List;
      --  Components is the list of the record components whose value must
      --  be provided in the aggregate. This list does include discriminants.

   --  Start processing for Resolve_Record_Aggregate

   begin
      --  We may end up calling Duplicate_Subexpr on expressions that are
      --  attached to New_Assoc_List. For this reason we need to attach it
      --  to the tree by setting its parent pointer to N. This parent point
      --  will change in STEP 8 below.

      Set_Parent (New_Assoc_List, N);

      --  STEP 1: abstract type and null record verification

      if Is_Abstract (Typ) then
         Error_Msg_N ("type of aggregate cannot be abstract",  N);
      end if;

      if No (First_Entity (Typ)) and then Null_Record_Present (N) then
         Set_Etype (N, Typ);
         return;

      elsif Present (First_Entity (Typ))
        and then Null_Record_Present (N)
        and then not Is_Tagged_Type (Typ)
      then
         Error_Msg_N ("record aggregate cannot be null", N);
         return;

      elsif No (First_Entity (Typ)) then
         Error_Msg_N ("record aggregate must be null", N);
         return;
      end if;

      --  STEP 2: Verify aggregate structure

      Step_2 : declare
         Selector_Name : Node_Id;
         Bad_Aggregate : Boolean := False;

      begin
         if Present (Component_Associations (N)) then
            Assoc := First (Component_Associations (N));
         else
            Assoc := Empty;
         end if;

         while Present (Assoc) loop
            Selector_Name := First (Choices (Assoc));
            while Present (Selector_Name) loop
               if Nkind (Selector_Name) = N_Identifier then
                  null;

               elsif Nkind (Selector_Name) = N_Others_Choice then
                  if Selector_Name /= First (Choices (Assoc))
                    or else Present (Next (Selector_Name))
                  then
                     Error_Msg_N ("OTHERS must appear alone in a choice list",
                                  Selector_Name);
                     return;

                  elsif Present (Next (Assoc)) then
                     Error_Msg_N ("OTHERS must appear last in an aggregate",
                                  Selector_Name);
                     return;
                  end if;

               else
                  Error_Msg_N
                    ("selector name should be identifier or OTHERS",
                     Selector_Name);
                  Bad_Aggregate := True;
               end if;

               Selector_Name := Next (Selector_Name);
            end loop;

            Assoc := Next (Assoc);
         end loop;

         if Bad_Aggregate then
            return;
         end if;
      end Step_2;

      --  STEP 3: Find discriminant Values

      Step_3 : declare
         Discrim               : Entity_Id;
         Missing_Discriminants : Boolean := False;

      begin
         if Present (Expressions (N)) then
            Positional_Expr := First (Expressions (N));
         else
            Positional_Expr := Empty;
         end if;

         if Has_Discriminants (Typ) then
            Discrim := First_Discriminant (Typ);
         else
            Discrim := Empty;
         end if;

         --  First find the discriminant values in the positional components

         while Present (Discrim) and then Present (Positional_Expr) loop
            if Discr_Present (Discrim) then
               Resolve_Aggr_Expr (Positional_Expr, Discrim);
               Positional_Expr := Next (Positional_Expr);
            end if;

            if Present (Get_Value (Discrim, Component_Associations (N))) then
               Error_Msg_NE
                 ("more than one value supplied for discriminant&",
                  N, Discrim);
            end if;

            Discrim := Next_Discriminant (Discrim);
         end loop;

         --  Find remaining discriminant values, if any, among named components

         while Present (Discrim) loop
            Expr := Get_Value (Discrim, Component_Associations (N), True);

            if not Discr_Present (Discrim) then
               if Present (Expr) then
                  Error_Msg_NE
                    ("more than one value supplied for discriminant&",
                     N, Discrim);
               end if;

            elsif No (Expr) then
               Error_Msg_NE
                 ("no value supplied for discriminant &", N, Discrim);
               Missing_Discriminants := True;

            else
               Resolve_Aggr_Expr (Expr, Discrim);
            end if;

            Discrim := Next_Discriminant (Discrim);
         end loop;

         if Missing_Discriminants then
            return;
         end if;

         --  At this point and until the beginning of STEP 6, New_Assoc_List
         --  contains only the discriminants and their values.

      end Step_3;

      --  STEP 4: Set the Etype of the record aggregate

      --  ?????? All this code to create the constrained type should be the
      --  same for the tagged and untagged case. For now we special case
      --  tagged type because this code is not working for tagged types
      --  where as it is working fot untagged types.

      if Has_Discriminants (Typ) and then not Is_Tagged_Type (Typ) then
         Build_Constrained_Itype : declare
            Discrim_Exprs : Elist_Id  := New_Elmt_List;

         begin
            Constr_Itype := Create_Itype (E_Record_Subtype, N);
            New_Assoc  := First (New_Assoc_List);
            while Present (New_Assoc) loop
               Append_Elmt (Duplicate_Subexpr (Expression (New_Assoc)),
                 Discrim_Exprs);
               New_Assoc  := Next (New_Assoc);
            end loop;

            Set_Etype                    (Constr_Itype, Base_Type      (Typ));
            Set_Size_Info                (Constr_Itype,                (Typ));
            Set_Is_Tagged_Type           (Constr_Itype, Is_Tagged_Type (Typ));
            Set_Has_Discriminants        (Constr_Itype, True);
            Set_Is_Constrained           (Constr_Itype, True);
            Set_First_Entity             (Constr_Itype, First_Entity   (Typ));
            Set_Last_Entity              (Constr_Itype, Last_Entity    (Typ));
            Conditional_Delay            (Constr_Itype,                (Typ));
            Set_Discriminant_Constraint  (Constr_Itype, Discrim_Exprs);

            Set_Girder_Constraint_From_Discriminant_Constraint (Constr_Itype);
            Set_Etype (N, Constr_Itype);
         end Build_Constrained_Itype;

      --  ??? This code is pretty much a copy of Sem_Ch3.Build_Subtype. That
      --  routine should really be exported in sem_util or some such and used
      --  in sem_ch3 and here rather than have a copy of the code which is a
      --  maintenance nightmare.

      elsif Has_Discriminants (Typ) and then Is_Tagged_Type (Typ) then
         Better_Way_To_Build_Constrained_Itype : declare
            Loc         : constant Source_Ptr := Sloc (N);
            Indic       : Node_Id;
            Subtyp_Decl : Node_Id;
            Def_Id      : Entity_Id;

            C : List_Id := New_List;

         begin
            New_Assoc := First (New_Assoc_List);
            while Present (New_Assoc) loop
               Append (Duplicate_Subexpr (Expression (New_Assoc)), To => C);
               New_Assoc := Next (New_Assoc);
            end loop;

            Indic :=
              Make_Subtype_Indication (Loc,
                Subtype_Mark => New_Occurrence_Of (Base_Type (Typ), Loc),
                Constraint  => Make_Index_Or_Discriminant_Constraint (Loc, C));

            Def_Id := Create_Itype (Ekind (Typ), N);

            Subtyp_Decl :=
              Make_Subtype_Declaration (Loc,
                Defining_Identifier => Def_Id,
                Subtype_Indication  => Indic);
            Set_Parent (Subtyp_Decl, Parent (N));

            --  Itypes must be analyzed with checks off (see itypes.ads).

            Analyze (Subtyp_Decl, Suppress => All_Checks);

            Set_Etype (N, Def_Id);
         end Better_Way_To_Build_Constrained_Itype;

      else
         Set_Etype (N, Typ);
      end if;

      --  STEP 5: Get remaining components according to discriminant values

      Step_5 : declare
         Record_Def      : Node_Id;
         Parent_Typ      : Entity_Id;
         Root_Typ        : Entity_Id;
         Parent_Typ_List : Elist_Id;
         Parent_Elmt     : Elmt_Id;
         Errors_Found    : Boolean := False;

      begin
         if Is_Derived_Type (Typ) and then Is_Tagged_Type (Typ) then
            Parent_Typ_List := New_Elmt_List;

            --  If this is an extension aggregate, the component list must
            --  include all components that are not in the given ancestor
            --  type. Otherwise,  the component list must include components
            --  of all ancestors.

            if Nkind (N) = N_Extension_Aggregate then
               Root_Typ := Base_Type (Etype (Ancestor_Part (N)));
            else
               Root_Typ := Root_Type (Typ);

               if Nkind (Parent (Base_Type (Root_Typ)))
                    = N_Private_Type_Declaration
               then
                  Error_Msg_NE
                    ("type of aggregate has private ancestor&!",
                     N, Root_Typ);
                  Error_Msg_N  ("must use extension aggregate!", N);
                  return;
               end if;

               Record_Def := Type_Definition (Parent (Base_Type (Root_Typ)));

               Gather_Components (Typ,
                 Component_List (Record_Def),
                 Governed_By   => New_Assoc_List,
                 Into          => Components,
                 Report_Errors => Errors_Found);
            end if;

            Parent_Typ  := Base_Type (Typ);
            while Parent_Typ /= Root_Typ loop

               Prepend_Elmt (Parent_Typ, To => Parent_Typ_List);
               Parent_Typ := Etype (Parent_Typ);

               if Nkind (Parent (Base_Type (Parent_Typ))) =
                                        N_Private_Type_Declaration
                 and then Nkind (N) /= N_Extension_Aggregate
               then
                  Error_Msg_NE
                    ("type of aggregate has private ancestor&!",
                     N, Parent_Typ);
                  Error_Msg_N  ("must use extension aggregate!", N);
                  return;
               end if;
            end loop;

            --  Now collect components from all other ancestors.

            Parent_Elmt := First_Elmt (Parent_Typ_List);
            while Present (Parent_Elmt) loop
               Parent_Typ := Node (Parent_Elmt);
               Record_Def := Type_Definition (Parent (Base_Type (Parent_Typ)));
               Gather_Components (Empty,
                 Component_List (Record_Extension_Part (Record_Def)),
                 Governed_By   => New_Assoc_List,
                 Into          => Components,
                 Report_Errors => Errors_Found);

               Parent_Elmt := Next_Elmt (Parent_Elmt);
            end loop;

         else
            Record_Def := Type_Definition (Parent (Base_Type (Typ)));

            if Null_Present (Record_Def) then
               null;
            else
               Gather_Components (Typ,
                 Component_List (Record_Def),
                 Governed_By   => New_Assoc_List,
                 Into          => Components,
                 Report_Errors => Errors_Found);
            end if;
         end if;

         if Errors_Found then
            return;
         end if;
      end Step_5;

      --  STEP 6: Find component Values

      Component_Elmt := First_Elmt (Components);

      --  First scan the remaining positional associations in the aggregate.
      --  Remember that at this point Positional_Expr contains the current
      --  positional association if any is left after looking for discriminant
      --  values in step 3.

      while Present (Positional_Expr) and then Present (Component_Elmt) loop
         Component := Node (Component_Elmt);
         Resolve_Aggr_Expr (Positional_Expr, Component);

         if Present (Get_Value (Component, Component_Associations (N))) then
            Error_Msg_NE
              ("more than one value supplied for Component &", N, Component);
         end if;

         Positional_Expr := Next (Positional_Expr);
         Component_Elmt  := Next_Elmt (Component_Elmt);
      end loop;

      if Present (Positional_Expr) then
         Error_Msg_N
           ("too many components for record aggregate", Positional_Expr);
      end if;

      --  Now scan for the named arguments of the aggregate

      while Present (Component_Elmt) loop
         Component := Node (Component_Elmt);
         Expr := Get_Value (Component, Component_Associations (N), True);

         if No (Expr) then
            Error_Msg_NE ("no value supplied for component &", N, Component);
         else
            Resolve_Aggr_Expr (Expr, Component);
         end if;

         Component_Elmt := Next_Elmt (Component_Elmt);
      end loop;

      --  STEP 7: check for invalid components + check type in choice list

      Step_7 : declare
         Selectr : Node_Id;
         --  Selector name

         Typech  : Entity_Id;
         --  Type of first component in choice list

      begin
         if Present (Component_Associations (N)) then
            Assoc := First (Component_Associations (N));
         else
            Assoc := Empty;
         end if;

         Verification : while Present (Assoc) loop
            Selectr := First (Choices (Assoc));
            Typech := Empty;

            if Nkind (Selectr) = N_Others_Choice then
               if No (Others_Etype) then
                  Error_Msg_N
                    ("OTHERS must represent at least one component", Selectr);
               end if;

               exit Verification;
            end if;

            while Present (Selectr) loop
               New_Assoc := First (New_Assoc_List);
               while Present (New_Assoc) loop
                  Component := First (Choices (New_Assoc));
                  exit when Chars (Selectr) = Chars (Component);
                  New_Assoc := Next (New_Assoc);
               end loop;

               --  If no association, this is not a a legal component of
               --  of the type in question,  except if this is an internal
               --  component supplied by a previous expansion.

               if No (New_Assoc) then

                  if Chars (Selectr) /= Name_uTag
                    and then Chars (Selectr) /= Name_uParent
                    and then Chars (Selectr) /= Name_uController
                  then
                     Error_Msg_N ("component & is undefined", Selectr);
                  end if;

               elsif No (Typech) then
                  Typech := Base_Type (Etype (Component));

               elsif Typech /= Base_Type (Etype (Component)) then
                  Error_Msg_N
                    ("components in choice list must have same type", Selectr);
               end if;

               Selectr := Next (Selectr);
            end loop;

            Assoc := Next (Assoc);
         end loop Verification;
      end Step_7;

      --  STEP 8: replace the original aggregate

      Step_8 : declare
         New_Aggregate : Node_Id := New_Copy (N);

      begin
         Set_Expressions            (New_Aggregate, No_List);
         Set_Etype                  (New_Aggregate, Etype (N));
         Set_Component_Associations (New_Aggregate, New_Assoc_List);

         Rewrite_Substitute_Tree (N, New_Aggregate);
      end Step_8;
   end Resolve_Record_Aggregate;

   -----------------------
   -- Gather_Components --
   -----------------------

   procedure Gather_Components
     (Typ           : Entity_Id;
      Comp_List     : Node_Id;
      Governed_By   : List_Id;
      Into          : Elist_Id;
      Report_Errors : out Boolean)
   is
      Assoc           : Node_Id;
      Variant         : Node_Id;
      Discrete_Choice : Node_Id;
      Comp_Item       : Node_Id;

      Discrim         : Entity_Id;
      Discrim_Name    : Node_Id;
      Discrim_Value   : Node_Id;
      C               : Entity_Id := Empty;

   begin
      Report_Errors := False;

      if No (Comp_List) or else Null_Present (Comp_List) then
         return;

      elsif Present (Component_Items (Comp_List)) then
         Comp_Item := First (Component_Items (Comp_List));

      else
         Comp_Item := Empty;
      end if;

      while Present (Comp_Item) loop

         --  Skip the tag of a tagged record, as well as all items
         --  that are not user components (anonymous types, rep clauses,
         --  Parent field, controller field).

         if Nkind (Comp_Item) = N_Component_Declaration
           and then Chars (Defining_Identifier (Comp_Item)) /= Name_uTag
           and then Chars (Defining_Identifier (Comp_Item)) /= Name_uParent
           and then Chars (Defining_Identifier (Comp_Item)) /= Name_uController
         then
            Append_Elmt (Defining_Identifier (Comp_Item), Into);
         end if;

         Comp_Item := Next (Comp_Item);
      end loop;

      if No (Variant_Part (Comp_List)) then
         return;
      else
         Discrim_Name := Name (Variant_Part (Comp_List));
         Variant := First_Non_Pragma (Variants (Variant_Part (Comp_List)));
      end if;

      --  Look for the discriminant that governs this variant part.
      --  The discriminant *must* be in the Governed_By List

      Assoc := First (Governed_By);
      loop
         Discrim := First (Choices (Assoc));
         exit when Chars (Discrim_Name) = Chars (Discrim);
         Assoc := Next (Assoc);
      end loop;

      Discrim_Value := Expression (Assoc);

      if not Is_OK_Static_Expression (Discrim_Value) then
         Error_Msg_NE
           ("value for discriminant & must be static", Discrim_Value, Discrim);
         Report_Errors := True;
         return;
      end if;

      Search_For_Discriminant_Value : declare
         Low  : Node_Id;
         High : Node_Id;

         UI_High          : Uint;
         UI_Low           : Uint;
         UI_Discrim_Value : constant Uint := Expr_Value (Discrim_Value);

      begin
         Find_Discrete_Value : while Present (Variant) loop
            Discrete_Choice := First (Discrete_Choices (Variant));
            while Present (Discrete_Choice) loop

               exit Find_Discrete_Value when
                 Nkind (Discrete_Choice) = N_Others_Choice;

               Get_Index_Bounds (Discrete_Choice, Low, High);

               UI_Low  := Expr_Value (Low);
               UI_High := Expr_Value (High);

               exit Find_Discrete_Value when
                 UI_Low <= UI_Discrim_Value
                   and then
                 UI_High >= UI_Discrim_Value;

               Discrete_Choice := Next (Discrete_Choice);
            end loop;

            Variant := Next_Non_Pragma (Variant);
         end loop Find_Discrete_Value;
      end Search_For_Discriminant_Value;

      if No (Variant) then
         Error_Msg_NE
           ("value of discriminant & is out of range", Discrim_Value, Discrim);
         Report_Errors := True;
         return;
      end  if;

      --  If we have found the corresponding choice, recursively add its
      --  components to the Into list.

      Gather_Components (Empty,
        Component_List (Variant), Governed_By, Into, Report_Errors);
   end Gather_Components;

   ------------------------
   -- Array_Aggr_Subtype --
   ------------------------

   function Array_Aggr_Subtype
     (N    : Node_Id;
      Typ  : Entity_Id)
      return Entity_Id
   is
      Aggr_Dimension : constant Pos := Number_Dimensions (Typ);
      --  Number of aggregate index dimensions.

      Aggr_Range : array (1 .. Aggr_Dimension) of Node_Id := (others => Empty);
      --  Constrained N_Range of each index dimension in our aggregate itype.

      Aggr_Low   : array (1 .. Aggr_Dimension) of Node_Id := (others => Empty);
      Aggr_High  : array (1 .. Aggr_Dimension) of Node_Id := (others => Empty);
      --  Low and High bounds for each index dimension in our aggregate itype.

      procedure Collect_Aggr_Bounds (N : Node_Id; Dim : Pos);
      --  N is an array (sub-)aggregate. Dim is the dimension corresponding to
      --  (sub-)aggregate N. This procedure collects the constrained N_Range
      --  nodes corresponding to each index dimension of our aggregate itype.
      --  These N_Range nodes are collected in Aggr_Range above.
      --  Likewise collect in Aggr_Low & Aggr_High above the low and high
      --  bounds of each index dimension. If, when collecting, two bounds
      --  corresponding to the same dimension are static and found to differ,
      --  then emit a warning, and mark N as raising Constraint_Error.

      -------------------------
      -- Collect_Aggr_Bounds --
      -------------------------

      procedure Collect_Aggr_Bounds (N : Node_Id; Dim : Pos) is
         This_Range : constant Node_Id := Aggregate_Bounds (N);
         --  The aggregate range node of this specific sub-aggregate.

         This_Low  : constant Node_Id := Low_Bound (Aggregate_Bounds (N));
         This_High : constant Node_Id := High_Bound (Aggregate_Bounds (N));
         --  The aggregate bounds of this specific sub-aggregate.

         Assoc  : Node_Id;
         Expr   : Node_Id;

      begin
         --  Collect the first N_Range for a given dimension that you find.
         --  For a given dimension they must be all equal anyway.

         if No (Aggr_Range (Dim)) then
            Aggr_Low (Dim)   := This_Low;
            Aggr_High (Dim)  := This_High;
            Aggr_Range (Dim) := This_Range;

         else
            if Compile_Time_Known_Value (This_Low) then
               if not Compile_Time_Known_Value (Aggr_Low (Dim)) then
                  Aggr_Low (Dim)  := This_Low;

               elsif Expr_Value (This_Low) /= Expr_Value (Aggr_Low (Dim)) then
                  Set_Raises_Constraint_Error (N);
                  Error_Msg_N ("Sub-aggregate low bound mismatch?", N);
                  Error_Msg_N ("Constraint_Error will be raised at run-time?",
                               N);
               end if;
            end if;

            if Compile_Time_Known_Value (This_High) then
               if not Compile_Time_Known_Value (Aggr_High (Dim)) then
                  Aggr_High (Dim)  := This_High;

               elsif
                 Expr_Value (This_High) /= Expr_Value (Aggr_High (Dim))
               then
                  Set_Raises_Constraint_Error (N);
                  Error_Msg_N ("Sub-aggregate high bound mismatch?", N);
                  Error_Msg_N ("Constraint_Error will be raised at run-time?",
                               N);
               end if;
            end if;
         end if;

         if Dim < Aggr_Dimension then

            --  Process positional components

            if Present (Expressions (N)) then
               Expr := First (Expressions (N));
               while Present (Expr) loop
                  Collect_Aggr_Bounds (Expr, Dim + 1);
                  Expr := Next (Expr);
               end loop;
            end if;

            --  Process component associations

            if Present (Component_Associations (N)) then
               Assoc := First (Component_Associations (N));
               while Present (Assoc) loop
                  Expr := Expression (Assoc);
                  Collect_Aggr_Bounds (Expr, Dim + 1);
                  Assoc := Next (Assoc);
               end loop;
            end if;
         end if;
      end Collect_Aggr_Bounds;

      --  Array_Aggr_Subtype variables

      Itype : Entity_Id;
      --  the final itype of the overall aggregate

      Index_Constraints : List_Id := New_List;
      --  The list of index constraints of the aggregate itype.

   --  Begin of Array_Aggr_Subtype

   begin
      --  Make sure that the list of index constraints is properly attached
      --  to the tree, and then collect the aggregate bounds.

      Set_Parent (Index_Constraints, N);
      Collect_Aggr_Bounds (N, 1);

      --  Build the list of constrained indices of our aggregate itype.

      for J in 1 .. Aggr_Dimension loop
         Create_Index : declare
            Index_Base : Entity_Id := Base_Type (Etype (Aggr_Range (J)));
            Index_Typ  : Entity_Id;

         begin
            --  Construct the Index subtype

            Index_Typ := Create_Itype (Subtype_Kind (Ekind (Index_Base)), N);

            Set_Etype (Index_Typ, Index_Base);

            if Is_Character_Type (Index_Base) then
               Set_Is_Character_Type (Index_Typ);
            end if;

            Set_Size_Info      (Index_Typ,                (Index_Base));
            Set_First_Rep_Item (Index_Typ, First_Rep_Item (Index_Base));
            Set_Scalar_Range   (Index_Typ, Aggr_Range (J));

            Set_Etype (Aggr_Range (J), Index_Typ);

            Append (Aggr_Range (J), To => Index_Constraints);
         end Create_Index;
      end loop;

      --  Now build the Itype

      Itype := Create_Itype (E_Array_Subtype, N);

      Set_First_Rep_Item         (Itype, First_Rep_Item         (Typ));
      Set_Component_Type         (Itype, Component_Type         (Typ));
      Set_Convention             (Itype, Convention             (Typ));
      Set_Depends_On_Private     (Itype, Has_Private_Component  (Typ));
      Set_Etype                  (Itype, Base_Type              (Typ));
      Set_Has_Alignment_Clause   (Itype, Has_Alignment_Clause   (Typ));
      Set_Is_Aliased             (Itype, Is_Aliased             (Typ));
      Set_Suppress_Index_Checks  (Itype, Suppress_Index_Checks  (Typ));
      Set_Suppress_Length_Checks (Itype, Suppress_Length_Checks (Typ));
      Set_Depends_On_Private     (Itype, Depends_On_Private     (Typ));

      Set_First_Index    (Itype, First (Index_Constraints));
      Set_Is_Constrained (Itype, True);
      Set_Is_Internal    (Itype, True);
      Set_Esize          (Itype, Uint_0);

      --  We always need a freeze node for a packed array subtype, so that
      --  we can build the Packed_Array_Type corresponding to the subtype.

      if Is_Packed (Itype) and then not In_Default_Expression then
         Freeze_Itype (Itype, N);
      end if;

      return Itype;
   end Array_Aggr_Subtype;

   ----------------------
   -- Constraint_Check --
   ----------------------

   procedure Constraint_Check (Exp : Node_Id; Check_Typ : Entity_Id) is
      Loc     : constant Source_Ptr := Sloc (Exp);
      Exp_Typ : constant Entity_Id  := Etype (Exp);

   begin
      if Raises_Constraint_Error (Exp) then
         return;
      end if;

      --  This is really expansion activity, so make sure that expansion
      --  is on and is allowed.

      if not Expander_Active or else In_Default_Expression then
         return;
      end if;

      --  First check if we have to insert discriminant checks

      if Nkind (Exp) = N_Aggregate and then Is_Record_Type (Exp_Typ) then

         --  If the record type is unconstrained or it has no discriminant
         --  constraints there are no discriminant checks to emit.

         if Discriminant_Checks_Suppressed (Check_Typ)
           or else not Has_Discriminants (Check_Typ)
           or else not Is_Constrained (Check_Typ)
         then
            return;
         end if;

         Discriminant_Check : declare
            Discr_Aggr  : Elmt_Id;
            Discr_Check : Elmt_Id;

            Cond : Node_Id := Empty;
            Test : Node_Id := Empty;

         begin
            Discr_Aggr  := First_Elmt (Discriminant_Constraint (Exp_Typ));
            Discr_Check := First_Elmt (Discriminant_Constraint (Check_Typ));

            while Present (Discr_Check) loop
               Test :=
                 Make_Op_Ne (Loc,
                   Left_Opnd  => Duplicate_Subexpr (Node (Discr_Aggr)),
                   Right_Opnd => Duplicate_Subexpr (Node (Discr_Check)));

               if No (Cond) then
                  Cond := Test;
               else
                  Cond := Make_Or_Else (Loc, Cond, Test);
               end if;

               Discr_Aggr  := Next_Elmt (Discr_Aggr);
               Discr_Check := Next_Elmt (Discr_Check);
            end loop;

            Insert_Action (Exp, Make_Raise_Constraint_Error (Loc, Cond));
         end Discriminant_Check;

      --  Next emit length checks for array aggregates

      elsif Nkind (Exp) = N_Aggregate and then Is_Array_Type (Exp_Typ) then

         if Length_Checks_Suppressed (Check_Typ)
           or else not Is_Constrained (Check_Typ)
         then
            return;
         end if;

         Length_Check : declare
            Check_Len_J : Node_Id;
            Exp_Len_J   : Node_Id;

            Cond : Node_Id := Empty;
            Test : Node_Id := Empty;

         begin
            for J in 1 .. Number_Dimensions (Check_Typ) loop
               Check_Len_J :=
                 Make_Attribute_Reference (Loc,
                   Prefix         => New_Reference_To (Check_Typ, Loc),
                   Attribute_Name => Name_Length,
                   Expressions    =>
                     New_List (Make_Integer_Literal (Loc, UI_From_Int (J))));

               Exp_Len_J :=
                 Make_Attribute_Reference (Loc,
                   Prefix         => New_Reference_To (Exp_Typ, Loc),
                   Attribute_Name => Name_Length,
                   Expressions    =>
                     New_List (Make_Integer_Literal (Loc, UI_From_Int (J))));

               Test :=
                 Make_Op_Ne (Loc,
                   Left_Opnd  => Check_Len_J,
                   Right_Opnd => Exp_Len_J);

               if No (Cond) then
                  Cond := Test;
               else
                  Cond := Make_Or_Else (Loc, Cond, Test);
               end if;
            end loop;

            Insert_Action (Exp, Make_Raise_Constraint_Error (Loc, Cond));
         end Length_Check;

      --  Finally emit scalar and string checks. If we are dealing with a
      --  scalar literal we need to check by hand because the Etype of
      --  literals is not necessarily correct.

      elsif Is_Scalar_Type (Exp_Typ)
        and then Compile_Time_Known_Value (Exp)
      then
         if Is_Out_Of_Range (Exp, Base_Type (Check_Typ)) then
            Apply_Compile_Time_Constraint_Error
              (Exp, "value not in range of}?", Base_Type (Check_Typ));

         elsif Is_Out_Of_Range (Exp, Check_Typ) then
            Apply_Compile_Time_Constraint_Error
              (Exp, "value not in range of}?", Check_Typ);

         elsif not Range_Checks_Suppressed (Check_Typ) then
            Check_Non_Static_Context (Exp);
            Apply_Scalar_Range_Check (Exp, Check_Typ);

         end if;

      elsif (Is_Scalar_Type (Exp_Typ)
             or else Nkind (Exp) = N_String_Literal)
        and then Exp_Typ /= Check_Typ
      then
         Rewrite_Substitute_Tree
           (Exp, Convert_To (Check_Typ, Relocate_Node (Exp)));
         Analyze_And_Resolve (Exp, Check_Typ);

      end if;
   end Constraint_Check;

   --------------------------------
   -- Make_String_Into_Aggregate --
   --------------------------------

   procedure Make_String_Into_Aggregate (N : Node_Id) is
      C          : Char_Code;
      C_Node     : Node_Id;
      Exprs      : List_Id := New_List;
      Loc        : constant Source_Ptr := Sloc (N);
      New_N      : Node_Id;
      P          : Source_Ptr := Loc + 1;
      Str        : constant String_Id  := Strval (N);
      Strlen     : constant Nat        := String_Length (Str);

   begin
      for J in  1 .. Strlen loop
         C := Get_String_Char (Str, J);
         Set_Character_Literal_Name (C);

         C_Node :=  Make_Character_Literal (P, Name_Find, C);
         Set_Etype (C_Node, Any_Character);
         Set_Analyzed (C_Node);
         Append_To (Exprs, C_Node);

         P := P + 1;
         --  something special for wide strings ?
      end loop;

      New_N := Make_Aggregate (Loc, Expressions => Exprs);
      Set_Analyzed (New_N);
      Set_Etype (New_N, Any_Composite);

      Rewrite_Substitute_Tree (N, New_N);
   end Make_String_Into_Aggregate;

   -----------------------------
   -- Resolve_Array_Aggregate --
   -----------------------------

   function Resolve_Array_Aggregate
     (N              : Node_Id;
      Index          : Node_Id;
      Index_Constr   : Node_Id;
      Component_Typ  : Entity_Id;
      Others_Allowed : Boolean)
      return           Boolean
   is
      Loc : constant Source_Ptr := Sloc (N);

      Failure : constant Boolean := False;
      Success : constant Boolean := True;

      Index_Typ      : constant Entity_Id := Etype (Index);
      Index_Typ_Low  : constant Node_Id   := Type_Low_Bound  (Index_Typ);
      Index_Typ_High : constant Node_Id   := Type_High_Bound (Index_Typ);
      --  The type of the index corresponding to the array sub-aggregate
      --  along with its low and upper bounds

      Index_Base      : constant Entity_Id := Base_Type (Index_Typ);
      Index_Base_Low  : constant Node_Id   := Type_Low_Bound (Index_Base);
      Index_Base_High : constant Node_Id   := Type_High_Bound (Index_Base);
      --  ditto for the base type

      Scalar_Component : constant Boolean := Is_Scalar_Type (Component_Typ);

      function Add (Val : Uint; To : Node_Id) return Node_Id;
      --  Creates a new expression node where Val is added to expression To.
      --  Tries to constant fold whenever possible. To must be an already
      --  analyzed expression.

      procedure Check_Bound (BH : Node_Id; AH : in out Node_Id);
      --  Checks that AH (the upper bound of an array aggregate) is <= BH
      --  (the upper bound of the index base type). If the check fails a
      --  warning is emitted, the Raises_Constraint_Error Flag of N is set,
      --  and AH is replaced with a duplicate of BH.

      procedure Check_Bounds (L, H : Node_Id; AL, AH : Node_Id);
      --  Checks that range AL .. AH is compatible with range L .. H. Emits a
      --  warning if not and sets the Raises_Constraint_Error Flag in N.

      procedure Check_Length (L, H : Node_Id; Len : Uint);
      --  Checks that range L .. H contains at least Len elements. Emits a
      --  warning if not and sets the Raises_Constraint_Error Flag in N.

      function Dynamic_Or_Null_Range (L, H : Node_Id) return Boolean;
      --  Returns True if range L .. H is dynamic or null.

      procedure Get (Value : out Uint; From : Node_Id; OK : out Boolean);
      --  Given expression node From, this routine sets OK to False if it
      --  cannot statically evaluate From. Otherwise it stores this static
      --  value into Value.

      function Index_Typ_First return Node_Id;
      --  Returns Index_Typ'First.

      function Resolve_Aggr_Expr
        (Expr        : Node_Id;
         Single_Elmt : Boolean)
         return        Boolean;
      --  Resolves aggregate expression Expr. Returs False if resolution
      --  fails.  If Single_Elmt is set to False, the expression Expr may be
      --  used to initialize several array aggregate elements (this can
      --  happen for discrete choices such as "L .. H => Expr" or the others
      --  choice). In this event we do not resolve Expr unless Expr is a
      --  scalar expresion or expansion is disabled.  To know why, see the
      --  DELAYED COMPONENT RESOLUTION note above.

      ---------
      -- Add --
      ---------

      function Add (Val : Uint; To : Node_Id) return Node_Id is
         Expr_Pos : Node_Id;
         Expr     : Node_Id;
         To_Pos   : Node_Id;

      begin
         if Raises_Constraint_Error (To) then
            return To;
         end if;

         --  First test if we can do constant folding

         if Compile_Time_Known_Value (To)
           or else Nkind (To) = N_Integer_Literal
         then
            Expr_Pos := Make_Integer_Literal (Loc, Expr_Value (To) + Val);
            Set_Is_Static_Expression (Expr_Pos);

            if not Is_Enumeration_Type (Index_Typ) then
               Expr := Expr_Pos;

            --  If we are dealing with enumeration return
            --     Index_Typ'Val (Expr_Pos)

            else
               Expr :=
                 Make_Attribute_Reference
                   (Loc,
                    Prefix         => New_Reference_To (Index_Typ, Loc),
                    Attribute_Name => Name_Val,
                    Expressions    => New_List (Expr_Pos));
            end if;

            return Expr;
         end if;

         --  If we are here no constant folding possible

         if not Is_Enumeration_Type (Index_Base) then
            Expr :=
              Make_Op_Add (Loc,
                           Left_Opnd  => Duplicate_Subexpr (To),
                           Right_Opnd => Make_Integer_Literal (Loc, Val));

         --  If we are dealing with enumeration return
         --    Index_Typ'Val (Index_Typ'Pos (To) + Val)

         else
            To_Pos :=
              Make_Attribute_Reference
                (Loc,
                 Prefix         => New_Reference_To (Index_Typ, Loc),
                 Attribute_Name => Name_Pos,
                 Expressions    => New_List (Duplicate_Subexpr (To)));

            Expr_Pos :=
              Make_Op_Add (Loc,
                           Left_Opnd  => To_Pos,
                           Right_Opnd => Make_Integer_Literal (Loc, Val));

            Expr :=
              Make_Attribute_Reference
                (Loc,
                 Prefix         => New_Reference_To (Index_Typ, Loc),
                 Attribute_Name => Name_Val,
                 Expressions    => New_List (Expr_Pos));
         end if;

         return Expr;
      end Add;

      -----------------
      -- Check_Bound --
      -----------------

      procedure Check_Bound (BH : Node_Id; AH : in out Node_Id) is
         Val_BH : Uint;
         Val_AH : Uint;

         OK_BH : Boolean;
         OK_AH : Boolean;

      begin
         Get (Value => Val_BH, From => BH, OK => OK_BH);
         Get (Value => Val_AH, From => AH, OK => OK_AH);

         if OK_BH and then OK_AH and then Val_BH < Val_AH then
            Set_Raises_Constraint_Error (N);
            Error_Msg_N ("upper bound out of range?", AH);
            Error_Msg_N ("Constraint_Error will be raised at run-time?", AH);

            --  You need to set AH to BH or else in the case of enumerations
            --  indices we will not be able to resolve the aggregate bounds.

            AH := Duplicate_Subexpr (BH);
         end if;
      end Check_Bound;

      ------------------
      -- Check_Bounds --
      ------------------

      procedure Check_Bounds (L, H : Node_Id; AL, AH : Node_Id) is
         Val_L  : Uint;
         Val_H  : Uint;
         Val_AL : Uint;
         Val_AH : Uint;

         OK_L  : Boolean;
         OK_H  : Boolean;
         OK_AL : Boolean;
         OK_AH : Boolean;

      begin
         if Raises_Constraint_Error (N)
           or else Dynamic_Or_Null_Range (AL, AH)
         then
            return;
         end if;

         Get (Value => Val_L, From => L, OK => OK_L);
         Get (Value => Val_H, From => H, OK => OK_H);

         Get (Value => Val_AL, From => AL, OK => OK_AL);
         Get (Value => Val_AH, From => AH, OK => OK_AH);

         if OK_L and then Val_L > Val_AL then
            Set_Raises_Constraint_Error (N);
            Error_Msg_N ("lower bound out of range?", AL);
            Error_Msg_N ("Constraint_Error will be raised at run-time?", AL);
         end if;

         if OK_H and then Val_H < Val_AH then
            Set_Raises_Constraint_Error (N);
            Error_Msg_N ("upper bound out of range?", AH);
            Error_Msg_N ("Constraint_Error will be raised at run-time?", AH);
         end if;
      end Check_Bounds;

      ------------------
      -- Check_Length --
      ------------------

      procedure Check_Length (L, H : Node_Id; Len : Uint) is
         Val_L  : Uint;
         Val_H  : Uint;

         OK_L  : Boolean;
         OK_H  : Boolean;

         Range_Len : Uint;

      begin
         if Raises_Constraint_Error (N) then
            return;
         end if;

         Get (Value => Val_L, From => L, OK => OK_L);
         Get (Value => Val_H, From => H, OK => OK_H);

         if not OK_L or else not OK_H then
            return;
         end if;

         --  If null range length is zero

         if Val_L > Val_H then
            Range_Len := Uint_0;
         else
            Range_Len := Val_H - Val_L + 1;
         end if;

         if Range_Len < Len then
            Set_Raises_Constraint_Error (N);
            Error_Msg_N ("Too many elements?", N);
            Error_Msg_N ("Constraint_Error will be raised at run-time?", N);
         end if;
      end Check_Length;

      ---------------------------
      -- Dynamic_Or_Null_Range --
      ---------------------------

      function Dynamic_Or_Null_Range (L, H : Node_Id) return Boolean is
         Val_L : Uint;
         Val_H : Uint;

         OK_L  : Boolean;
         OK_H  : Boolean;

      begin
         Get (Value => Val_L, From => L, OK => OK_L);
         Get (Value => Val_H, From => H, OK => OK_H);

         return not OK_L or else not OK_H
           or else not Is_OK_Static_Expression (L)
           or else not Is_OK_Static_Expression (H)
           or else Val_L > Val_H;
      end Dynamic_Or_Null_Range;

      ---------
      -- Get --
      ---------

      procedure Get (Value : out Uint; From : Node_Id; OK : out Boolean) is
      begin
         OK := True;

         if Compile_Time_Known_Value (From) then
            Value := Expr_Value (From);

         --  If expression From is something like Some_Type'Val (10) then
         --  Value = 10

         elsif Nkind (From) = N_Attribute_Reference
           and then Attribute_Name (From) = Name_Val
           and then Compile_Time_Known_Value (First (Expressions (From)))
         then
            Value := Expr_Value (First (Expressions (From)));

         else
            Value := Uint_0;
            OK := False;

         end if;
      end Get;

      ---------------------
      -- Index_Typ_First --
      ---------------------

      function Index_Typ_First return Node_Id is
      begin
         return
           Make_Attribute_Reference
             (Loc,
              Prefix         => New_Reference_To (Index_Typ, Loc),
              Attribute_Name => Name_First);
      end Index_Typ_First;

      -----------------------
      -- Resolve_Aggr_Expr --
      -----------------------

      function Resolve_Aggr_Expr
        (Expr        : Node_Id;
         Single_Elmt : Boolean)
         return        Boolean
      is
         Nxt_Ind        : Node_Id := Next_Index (Index);
         Nxt_Ind_Constr : Node_Id := Next_Index (Index_Constr);
         --  Index is the current index corresponding to the expresion.

         Resolution_OK : Boolean := True;
         --  Set to False if resolution of the expression failed.

      begin
         --  If the array type against which we are resolving the aggregate
         --  has several dimensions, the expressions nested inside the
         --  aggregate must be further aggregates (or strings).

         if Present (Nxt_Ind) then
            if Nkind (Expr) /= N_Aggregate then

               --  A string literal can appear where a one-dimensional array
               --  of characters is expected.

               if Is_Character_Type (Component_Typ)
                 and then No (Next_Index (Nxt_Ind))
                 and then Nkind (Expr) = N_String_Literal
               then
                  --  A string literal used in a multidimensional array
                  --  aggregate in place of the final one-dimensional
                  --  aggregate must not be enclosed in parentheses.

                  if Paren_Count (Expr) /= 0 then
                     Error_Msg_N ("No parenthesis allowed here", Expr);
                  end if;

                  Make_String_Into_Aggregate (Expr);

               else
                  Error_Msg_N ("nested array aggregate expected", Expr);
                  return Failure;

               end if;
            end if;

            Resolution_OK := Resolve_Array_Aggregate
              (Expr, Nxt_Ind, Nxt_Ind_Constr, Component_Typ, Others_Allowed);

         --  Do not resolve the expressions of discrete or others choices
         --  unless the expression is scalar or the expander in inactive

         elsif Single_Elmt
           or else Scalar_Component
           or else not Expander_Active
           or else In_Default_Expression
         then
            Analyze_And_Resolve (Expr, Component_Typ);
            Constraint_Check (Expr, Component_Typ);

         end if;

         if Raises_Constraint_Error (Expr) then
            Set_Raises_Constraint_Error (N);
         end if;

         return Resolution_OK;
      end Resolve_Aggr_Expr;

      --  Variables local to Resolve_Array_Aggregate

      Assoc   : Node_Id;
      Choice  : Node_Id;
      Expr    : Node_Id;

      Who_Cares : Node_Id;

      Aggr_Low  : Node_Id := Empty;
      Aggr_High : Node_Id := Empty;
      --  The actual low and high bounds of this sub-aggegate

      Choices_Low  : Node_Id := Empty;
      Choices_High : Node_Id := Empty;
      --  The lowest and highest discrete choices values for a named aggregate

      Nb_Elements : Uint := Uint_0;
      --  The number of elements in a positional aggegate

      Others_Present : Boolean := False;

      Nb_Choices : Nat := 0;
      --  Contains the overall number of named choices in this sub-aggregate

      Nb_Discrete_Choices : Nat := 0;
      --  The overall number of discrete choices (not counting others choice)

      Case_Table_Size : Nat;
      --  Contains the size of the case table needed to sort aggregate choices

   --  Begin of Resolve_Array_Aggregate

   begin
      --  STEP 1: make sure the aggregate is correctly formatted

      if Present (Component_Associations (N)) then
         Assoc := First (Component_Associations (N));
         while Present (Assoc) loop
            Choice := First (Choices (Assoc));
            while Present (Choice) loop
               if Nkind (Choice) = N_Others_Choice then
                  Others_Present := True;

                  if Choice /= First (Choices (Assoc))
                    or else Present (Next (Choice))
                  then
                     Error_Msg_N ("OTHERS must appear alone in a choice list",
                                  Choice);
                     return Failure;
                  end if;

                  if Present (Next (Assoc)) then
                     Error_Msg_N ("OTHERS must appear last in an aggregate",
                                  Choice);
                     return Failure;
                  end if;
               end if;

               Nb_Choices := Nb_Choices + 1;
               Choice     := Next (Choice);
            end loop;

            Assoc := Next (Assoc);
         end loop;
      end if;

      --  At this point we know that the others choice, if present, is by
      --  itself and appears last in the aggregate.  Check if we have mixed
      --  positional and discrete associations (other than the others choice).

      if Present (Expressions (N))
        and then (Nb_Choices > 1
                  or else (Nb_Choices = 1 and then not Others_Present))
      then
         Error_Msg_N
           ("named association cannot follow positional association",
            First (Choices (First (Component_Associations (N)))));
         return Failure;
      end if;

      --  Test for the validity of an others choice if present

      if Others_Present and then not Others_Allowed then
         Error_Msg_N ("OTHERS choice not allowed here",
                      First (Choices (First (Component_Associations (N)))));
         return Failure;
      end if;

      --  STEP 2: Process named components

      if No (Expressions (N)) then

         if Others_Present then
            Case_Table_Size := Nb_Choices - 1;
         else
            Case_Table_Size := Nb_Choices;
         end if;

         Step_2 : declare
            Low  : Node_Id;
            High : Node_Id;
            --  Denote the lowest and highest values in an aggregate choice

            S_Low  : Node_Id := Empty;
            S_High : Node_Id := Empty;
            --  if a choice in an aggregate is a subtype indication these
            --  denote the lowest and highest values of the subtype

            Table : Case_Table_Type (1 .. Case_Table_Size);
            --  Used to sort all the different choice values

            Original_Choice : Node_Id;

            Single_Choice : Boolean;
            --  Set to true every time there is a single discrete choice in a
            --  discrete association

            Prev_Nb_Discrete_Choices : Nat;
            --  Used to keep track of the number of discrete choices
            --  in the current association.

         begin
            --  STEP 2 (A): Check discrete choices validity.

            Assoc := First (Component_Associations (N));
            while Present (Assoc) loop

               Prev_Nb_Discrete_Choices := Nb_Discrete_Choices;
               Choice := First (Choices (Assoc));
               while Present (Choice) loop
                  Analyze (Choice);

                  if Nkind (Choice) = N_Others_Choice then
                     exit;

                  --  Test for subtype mark without constraint

                  elsif Is_Entity_Name (Choice) and then
                    Is_Type (Entity (Choice))
                  then
                     if Base_Type (Entity (Choice)) /= Index_Base then
                        Error_Msg_N
                          ("invalid subtype mark in aggregate choice", Choice);
                        return Failure;
                     end if;

                  elsif Nkind (Choice) = N_Subtype_Indication then
                     Resolve_Discrete_Subtype_Indication (Choice, Index_Typ);

                     --  Does the subtype indication evaluation raise CE ?

                     Get_Index_Bounds (Subtype_Mark (Choice), S_Low, S_High);
                     Get_Index_Bounds (Choice, Low, High);
                     Check_Bounds (S_Low, S_High, Low, High);

                  else  --  Choice is a range or an expression
                     Resolve (Choice, Index_Typ);
                     Check_Non_Static_Context (Choice);

                     --  Do not range check a choice. This check is redundant
                     --  since this test is already performed when we check
                     --  that the bounds of the array aggregate are within
                     --  range.

                     Set_Do_Range_Check (Choice, False);

                  end if;

                  --  If we could not resolve the discrete choice stop here

                  if Etype (Choice) = Any_Type then
                     return Failure;

                  --  If the discrete choice raises CE get its original bounds.

                  elsif Nkind (Choice) = N_Raise_Constraint_Error then
                     Set_Raises_Constraint_Error (N);
                     Get_Index_Bounds (Original_Node (Choice), Low, High);

                  --  Otherwise get its bounds as usual

                  else
                     Get_Index_Bounds (Choice, Low, High);

                  end if;

                  if (Dynamic_Or_Null_Range (Low, High)
                      or else (Nkind (Choice) = N_Subtype_Indication
                               and then Dynamic_Or_Null_Range (S_Low, S_High)))
                    and then Nb_Choices /= 1
                  then
                     Error_Msg_N ("dynamic or empty choice in aggregate " &
                                  "must be the only choice", Choice);
                     return Failure;
                  end if;

                  Nb_Discrete_Choices := Nb_Discrete_Choices + 1;
                  Table (Nb_Discrete_Choices).Choice_Lo := Low;
                  Table (Nb_Discrete_Choices).Choice_Hi := High;

                  Choice := Next (Choice);
               end loop;

               --  Check if we have a single discrete choice and if yes, check
               --  whether this discrete choice specified a single value.

               Single_Choice :=
                 (Nb_Discrete_Choices = Prev_Nb_Discrete_Choices + 1)
                 and then (Low = High);

               if not Resolve_Aggr_Expr (Expression (Assoc),
                                         Single_Elmt => Single_Choice)
               then
                  return Failure;
               end if;

               Assoc := Next (Assoc);
            end loop;

            --  If aggregate contains more than one choice then these must be
            --  static. Sort them and check that they are contiguous

            if Nb_Discrete_Choices > 1 then
               Sort_Case_Table (Table);

               for J in 1 .. Nb_Discrete_Choices - 1 loop
                  if Expr_Value (Table (J).Choice_Hi) >=
                    Expr_Value (Table (J + 1).Choice_Lo)
                  then
                     Error_Msg_N ("duplicate choice values in array aggregate",
                                  Table (J).Choice_Hi);
                     return Failure;

                  elsif (not Others_Present)
                    and then
                    (Expr_Value (Table (J + 1).Choice_Lo) -
                     Expr_Value (Table (J).Choice_Hi)) > 1
                  then
                     Error_Msg_N ("missing association in array aggregate", N);
                     Set_Etype (N, Any_Composite);
                     return Failure;

                  end if;
               end loop;
            end if;

            --  STEP 2 (B): Compute aggregate bounds and min/max choices values

            if Nb_Discrete_Choices > 0 then
               Choices_Low  := Table (1).Choice_Lo;
               Choices_High := Table (Nb_Discrete_Choices).Choice_Hi;
            end if;

            if Others_Present then
               Get_Index_Bounds (Index_Constr, Aggr_Low, Aggr_High);

            else
               Aggr_Low  := Choices_Low;
               Aggr_High := Choices_High;
            end if;
         end Step_2;

      --  STEP 3: Process positional components

      else
         --  STEP 3 (A): Process positional elements

         Expr := First (Expressions (N));
         Nb_Elements := Uint_0;
         while Present (Expr) loop
            Nb_Elements := Nb_Elements + 1;

            if not Resolve_Aggr_Expr (Expr, Single_Elmt => True) then
               return Failure;
            end if;

            Expr := Next (Expr);
         end loop;

         if Others_Present then
            Assoc := Last (Component_Associations (N));
            if not Resolve_Aggr_Expr (Expression (Assoc),
                                      Single_Elmt => False)
            then
               return Failure;
            end if;
         end if;

         --  STEP 3 (B): Compute the aggregate bounds

         if Others_Present then
            Get_Index_Bounds (Index_Constr, Aggr_Low, Aggr_High);

         else
            if Others_Allowed then
               Get_Index_Bounds (Index_Constr, Aggr_Low, Who_Cares);
            else
               Aggr_Low := Index_Typ_Low;
            end if;

            Aggr_High := Add (Nb_Elements - 1, To => Aggr_Low);
            Check_Bound (Index_Base_High, Aggr_High);
         end if;
      end if;

      --  STEP 4: Perform static aggregate checks and save the bounds

      --  Check (A)

      Check_Bounds (Index_Typ_Low, Index_Typ_High, Aggr_Low, Aggr_High);
      Check_Bounds (Index_Base_Low, Index_Base_High, Aggr_Low, Aggr_High);

      --  Check (B)

      if Others_Present and then Nb_Discrete_Choices > 0 then
         Check_Bounds (Aggr_Low, Aggr_High, Choices_Low, Choices_High);
         Check_Bounds (Index_Typ_Low, Index_Typ_High,
                       Choices_Low, Choices_High);
         Check_Bounds (Index_Base_Low, Index_Base_High,
                       Choices_Low, Choices_High);

      --  Check (C)

      elsif Others_Present and then Nb_Elements > 0 then
         Check_Length (Aggr_Low, Aggr_High, Nb_Elements);
         Check_Length (Index_Typ_Low, Index_Typ_High, Nb_Elements);
         Check_Length (Index_Base_Low, Index_Base_High, Nb_Elements);

      end if;

      if Raises_Constraint_Error (Aggr_Low)
        or else Raises_Constraint_Error (Aggr_High)
      then
         Set_Raises_Constraint_Error (N);
      end if;

      Aggr_Low := Duplicate_Subexpr (Aggr_Low);

      --  Do not duplicate Aggr_High if Aggr_High = Aggr_Low + Nb_Elements
      --  since the addition node returned by Add is not yet analyzed. Attach
      --  to tree and analyze first.

      if Others_Present or else Nb_Discrete_Choices > 0 then
         Aggr_High := Duplicate_Subexpr (Aggr_High);
      end if;

      Set_Aggregate_Bounds
        (N, Make_Range (Loc, Low_Bound => Aggr_Low, High_Bound => Aggr_High));

      --  The bounds may contain expressions that must be inserted upwards.
      --  Attach them fully to the tree. After analysis, remove side effects
      --  from upper bound, if still needed.

      Set_Parent (Aggregate_Bounds (N), N);
      Analyze_And_Resolve (Aggregate_Bounds (N), Index_Typ);

      if not Others_Present and then Nb_Discrete_Choices = 0 then
         Set_High_Bound (Aggregate_Bounds (N),
             Duplicate_Subexpr (High_Bound (Aggregate_Bounds (N))));
      end if;

      return Success;
   end Resolve_Array_Aggregate;

end Sem_Aggr;
