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-- --
-- --
-- S E M _ D I S P --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2018, 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 --
-- 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. --
-- --
-- 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. Issues appropriate error messages if
-- any of these requirements is not met.
procedure Check_Dispatching_Call (N : Node_Id);
-- Check if the call N 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 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.
-- Need more description here, what are the parameters, and what does
-- this call actually do???
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 Old_Subp is adjusted to point to the inherited procedure of the
-- full view because it is always this one which has to be called.
-- What is Subp used for???
function Covered_Interface_Op (Prim : Entity_Id) return Entity_Id;
-- Returns the interface primitive that Prim covers, when its controlling
-- type has progenitors.
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 the subprogram Subp 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 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;
No_Interfaces : Boolean := False;
Interfaces_Only : Boolean := False;
One_Only : Boolean := False) return Subprogram_List;
-- Given the spec of a subprogram, this function gathers any inherited
-- subprograms from direct inheritance or via interfaces. The result is an
-- array of Entity_Ids 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). If
-- No_Interfaces is True, only return inherited subprograms not coming
-- from an interface. If Interfaces_Only is True, only return inherited
-- subprograms from interfaces. Otherwise, subprograms inherited directly
-- come first, starting with the closest ancestors, and are followed by
-- subprograms inherited from interfaces. At most one of No_Interfaces
-- and Interfaces_Only should be True.
-- If One_Only is set, the search is discontinued as soon as one entry
-- is found. In this case the resulting array is either null or contains
-- exactly one element.
function Is_Dynamically_Tagged (N : Node_Id) return Boolean;
-- Used to determine whether a call is dispatching, i.e. if it is
-- an expression of a class_Wide type, or a call to a function with
-- controlling result where at least one operand is dynamically tagged.
-- Also used to determine whether an entity has a class-wide type, or a
-- function call that dispatches on the result. Used to verify that all the
-- dependent expressions in a conditional expression are equally 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_Overriding_Subprogram (E : Entity_Id) return Boolean;
-- Returns True if E is an overriding subprogram
function Is_Tag_Indeterminate (N : Node_Id) return Boolean;
-- Returns true if the expression N is tag-indeterminate. 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;
Is_Wrapper : Boolean := False);
-- Replace an implicit dispatching operation of the type Tagged_Type
-- with an explicit one. Prev_Op is an inherited primitive operation which
-- is overridden by the explicit declaration of New_Op. Is_Wrapper is
-- True when New_Op is an internally generated wrapper of a controlling
-- function. The caller checks that Tagged_Type is indeed a tagged type.
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.
-- Need clear description of the parameters Control and Actual, especially
-- since the comments above refer to actuals in the plural ???
end Sem_Disp;