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--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                             S E M _ D I S P                              --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2010, 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 3,  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 COPYING3.  If not, go to --

-- http://www.gnu.org/licenses for a complete copy of the license.          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

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--  This package contains routines involved in tagged types and dynamic

--  dispatching.

with Types; use Types;

package Sem_Disp is

   procedure Check_Controlling_Formals (Typ : Entity_Id; Subp : Entity_Id);

   --  Check that all controlling parameters of Subp are of type Typ,

   --  that defaults for controlling parameters are tag-indeterminate,

   --  and that the nominal subtype of the parameters and result

   --  statically match the first subtype of the controlling type.

   procedure Check_Dispatching_Call (N : Node_Id);

   --  Check if a call is a dispatching call. The subprogram is known to

   --  be a dispatching operation. The call is dispatching if all the

   --  controlling actuals are dynamically tagged. This procedure is called

   --  after overload resolution, so the call is known to be unambiguous.

   procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id);

   --  Add "Subp" to the list of primitive operations of the corresponding type

   --  if it has a parameter of this type and is defined at a proper place for

   --  primitive operations (new primitives are only defined in package spec,

   --  overridden operation can be defined in any scope). If Old_Subp is not

   --  Empty we are in the overriding case. If the tagged type associated with

   --  Subp is a concurrent type (case that occurs when the type is declared in

   --  a generic because the analysis of generics disables generation of the

   --  corresponding record) then this routine does does not add "Subp" to the

   --  list of primitive operations but leaves Subp decorated as dispatching

   --  operation to enable checks associated with the Object.Operation notation

   procedure Check_Operation_From_Incomplete_Type

     (Subp : Entity_Id;

      Typ  : Entity_Id);

   --  If a primitive operation was defined for the incomplete view of the

   --  type, and the full type declaration is a derived type definition,

   --  the operation may override an inherited one.

   procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id);

   --  Add "Old_Subp" to the list of primitive operations of the corresponding

   --  tagged type if it is the full view of a private tagged type. The Alias

   --  of "OldSubp" is adjusted to point to the inherited procedure of the

   --  full view because it is always this one which has to be called.

   function Covers_Some_Interface (Prim : Entity_Id) return Boolean;

   --  Returns true if Prim covers some interface primitive of its associated

   --  tagged type. The tagged type of Prim must be frozen when this function

   --  is invoked.

   function Find_Controlling_Arg (N : Node_Id) return Node_Id;

   --  Returns the actual controlling argument if N is dynamically tagged,

   --  and Empty if it is not dynamically tagged.

   function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id;

   --  Check whether a subprogram is dispatching, and find the tagged type of

   --  the controlling argument or arguments. Returns Empty if Subp is not a

   --  dispatching operation.

   function Find_Primitive_Covering_Interface

     (Tagged_Type : Entity_Id;

      Iface_Prim  : Entity_Id) return Entity_Id;

   --  Search in the homonym chain for the primitive of Tagged_Type that covers

   --  Iface_Prim. The homonym chain traversal is required to catch primitives

   --  associated with the partial view of private types when processing the

   --  corresponding full view. If the entity is not found then search for it

   --  in the list of primitives of Tagged_Type. This latter search is needed

   --  when the interface primitive is covered by a private subprogram. If the

   --  primitive has not been covered yet then return the entity that will be

   --  overridden when the primitive is covered (that is, return the entity

   --  whose alias attribute references the interface primitive). If none of

   --  these entities is found then return Empty.

   type Subprogram_List is array (Nat range <>) of Entity_Id;

   --  Type returned by Inherited_Subprograms function

   function Inherited_Subprograms (S : Entity_Id) return Subprogram_List;

   --  Given the spec of a subprogram, this function gathers any inherited

   --  subprograms from direct inheritance or via interfaces. The list is

   --  a list of entity id's of the specs of inherited subprograms. Returns

   --  a null array if passed an Empty spec id. Note that the returned array

   --  only includes subprograms and generic subprograms (and excludes any

   --  other inherited entities, in particular enumeration literals).

   function Is_Dynamically_Tagged (N : Node_Id) return Boolean;

   --  Used to determine whether a call is dispatching, i.e. if is an

   --  an expression of a class_Wide type, or a call to a function with

   --  controlling result where at least one operand is dynamically tagged.

   function Is_Null_Interface_Primitive (E : Entity_Id) return Boolean;

   --  Returns True if E is a null procedure that is an interface primitive

   function Is_Tag_Indeterminate (N : Node_Id) return Boolean;

   --  An expression is tag-indeterminate if it is a call that dispatches

   --  on result, and all controlling operands are also indeterminate.

   --  Such a function call may inherit a tag from an enclosing call.

   procedure Override_Dispatching_Operation

     (Tagged_Type : Entity_Id;

      Prev_Op     : Entity_Id;

      New_Op      : Entity_Id);

   --  Replace an implicit dispatching operation with an explicit one.

   --  Prev_Op is an inherited primitive operation which is overridden

   --  by the explicit declaration of New_Op.

   procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id);

   --  If a function call is tag-indeterminate,  its controlling argument is

   --  found in the context;  either an enclosing call, or the left-hand side

   --  of the enclosing assignment statement. The tag must be propagated

   --  recursively to the tag-indeterminate actuals of the call.

end Sem_Disp;