[Ada] Ada2022: AI12-0195 overriding class-wide pre/postconditions

gcc/ada/

	* contracts.ads (Make_Class_Precondition_Subps): New subprogram.
	(Merge_Class_Conditions): New subprogram.
	(Process_Class_Conditions_At_Freeze_Point): New subprogram.

	* contracts.adb (Check_Class_Condition): New subprogram.
	(Set_Class_Condition): New subprogram.
	(Analyze_Contracts): Remove code analyzing class-wide-clone
	subprogram since it is no longer built.
	(Process_Spec_Postconditions): Avoid processing twice seen
	subprograms.
	(Process_Preconditions): Simplify its functionality to
	non-class-wide preconditions.
	(Process_Preconditions_For): No action needed for wrappers and
	helpers.
	(Make_Class_Precondition_Subps): New subprogram.
	(Process_Class_Conditions_At_Freeze_Point): New subprogram.
	(Merge_Class_Conditions): New subprogram.
	* exp_ch6.ads (Install_Class_Preconditions_Check): New
	subprogram.
	* exp_ch6.adb (Expand_Call_Helper): Install class-wide
	preconditions check on dispatching primitives that have or
	inherit class-wide preconditions.
	(Freeze_Subprogram): Remove code for null procedures with
	preconditions.
	(Install_Class_Preconditions_Check): New subprogram.
	* exp_util.ads (Build_Class_Wide_Expression): Lower the
	complexity of this subprogram; out-mode formal Needs_Wrapper
	since this functionality is now provided by a new subprogram.
	(Get_Mapped_Entity): New subprogram.
	(Map_Formals): New subprogram.
	* exp_util.adb (Build_Class_Wide_Expression): Lower the
	complexity of this subprogram. Its previous functionality is now
	provided by subprograms Needs_Wrapper and Check_Class_Condition.
	(Add_Parent_DICs): Map the overridden primitive to the
	overriding one.
	(Get_Mapped_Entity): New subprogram.
	(Map_Formals): New subprogram.
	(Update_Primitives_Mapping): Adding assertion.
	* freeze.ads (Check_Inherited_Conditions): Subprogram made
	public with added formal to support late overriding.
	* freeze.adb (Check_Inherited_Conditions): New implementation;
	builds the dispatch table wrapper required for class-wide
	pre/postconditions; added support for late overriding.
	(Needs_Wrapper): New subprogram.
	* sem.ads (Inside_Class_Condition_Preanalysis): New global
	variable.
	* sem_disp.ads (Covered_Interface_Primitives): New subprogram.
	* sem_disp.adb (Covered_Interface_Primitives): New subprogram.
	(Check_Dispatching_Context): Skip checking context of
	dispatching calls during preanalysis of class-wide conditions
	since at that stage the expression is not installed yet on its
	definite context.
	(Check_Dispatching_Call): Skip checking 6.1.1(18.2/5) by
	AI12-0412 on helpers and wrappers internally built for
	supporting class-wide conditions; for late-overriding
	subprograms call Check_Inherited_Conditions to build the
	dispatch-table wrapper (if required).
	(Propagate_Tag): Adding call to
	Install_Class_Preconditions_Check.
	* sem_util.ads (Build_Class_Wide_Clone_Body): Removed.
	(Build_Class_Wide_Clone_Call): Removed.
	(Build_Class_Wide_Clone_Decl): Removed.
	(Class_Condition): New subprogram.
	(Nearest_Class_Condition_Subprogram): New subprogram.
	* sem_util.adb (Build_Class_Wide_Clone_Body): Removed.
	(Build_Class_Wide_Clone_Call): Removed.
	(Build_Class_Wide_Clone_Decl): Removed.
	(Class_Condition): New subprogram.
	(Nearest_Class_Condition_Subprogram): New subprogram.
	(Eligible_For_Conditional_Evaluation): No need to evaluate
	class-wide conditions during preanalysis since the expression is
	not installed on its definite context.
	* einfo.ads (Class_Wide_Clone): Removed.
	(Class_Postconditions): New attribute.
	(Class_Preconditions): New attribute.
	(Class_Preconditions_Subprogram): New attribute.
	(Dynamic_Call_Helper): New attribute.
	(Ignored_Class_Postconditions): New attribute.
	(Ignored_Class_Preconditions): New attribute.
	(Indirect_Call_Wrapper): New attribute.
	(Is_Dispatch_Table_Wrapper): New attribute.
	(Static_Call_Helper): New attribute.
	* exp_attr.adb (Expand_N_Attribute_Reference): When the prefix
	is of an access-to-subprogram type that has class-wide
	preconditions and an indirect-call wrapper of such subprogram is
	available, replace the prefix by the wrapper.
	* exp_ch3.adb (Build_Class_Condition_Subprograms): New
	subprogram.
	(Register_Dispatch_Table_Wrappers): New subprogram.
	* exp_disp.adb (Build_Class_Wide_Check): Removed; class-wide
	precondition checks now rely on internally built helpers.
	* sem_ch13.adb (Analyze_Aspect_Specifications): Set initial
	value of attributes Class_Preconditions, Class_Postconditions,
	Ignored_Class_Preconditions and Ignored_Class_Postconditions.
	These values are later updated with the full pre/postcondition
	by Merge_Class_Conditions.
	(Freeze_Entity_Checks): Call
	Process_Class_Conditions_At_Freeze_Point.
	* sem_ch6.adb (Analyze_Subprogram_Body_Helper): Remove code
	building the body of the class-wide clone subprogram since it is
	no longer required.
	(Install_Entity): Adding assertion.
	* sem_prag.adb (Analyze_Pre_Post_Condition_In_Decl_Part): Remove
	code building and analyzing the class-wide clone subprogram; no
	longer required.
	(Build_Pragma_Check_Equivalent): Adjust call to
	Build_Class_Wide_Expression since the formal named Needs_Wrapper
	has been removed.
	* sem_attr.adb (Analyze_Attribute_Old_Result): Skip processing
	these attributes during preanalysis of class-wide conditions
	since at that stage the expression is not installed yet on its
	definite context.
	* sem_res.adb (Resolve_Actuals): Skip applying RM 3.9.2(9/1) and
	SPARK RM 6.1.7(3) on actuals of internal helpers and wrappers
	built to support class-wide preconditions.
	* sem_ch5.adb (Process_Bounds): Do not generate a constant
	declaration for the bounds when we are preanalyzing a class-wide
	condition.
	(Analyze_Loop_Parameter_Specification): Handle preanalysis of
	quantified expression placed in the outermost expression of a
	class-wide condition.
	* ghost.adb (Check_Ghost_Context): No check required during
	preanalysis of class-wide conditions.
	* gen_il-fields.ads (Opt_Field_Enum): Adding
	Class_Postconditions, Class_Preconditions,
	Class_Preconditions_Subprogram, Dynamic_Call_Helper,
	Ignored_Class_Postconditions, Ignored_Class_Preconditions,
	Indirect_Call_Wrapper, Is_Dispatch_Table_Wrapper,
	Static_Call_Helper.
	* gen_il-gen-gen_entities.adb (Is_Dispatch_Table_Wrapper):
	Adding semantic flag Is_Dispatch_Table_Wrapper; removing
	semantic field Class_Wide_Clone; adding semantic fields for
	Class_Postconditions, Class_Preconditions,
	Class_Preconditions_Subprogram, Dynamic_Call_Helper,
	Ignored_Class_Postconditions, Indirect_Call_Wrapper,
	Ignored_Class_Preconditions, and Static_Call_Helper.

1 files changed, 1 insertions, 23 deletions

diff --git a/gcc/ada/sem_ch6.adb b/gcc/ada/sem_ch6.adb
index 02928342744..1fcbdfbf918 100644
--- a/gcc/ada/sem_ch6.adb
+++ b/gcc/ada/sem_ch6.adb
@@ -4498,29 +4498,6 @@ package body Sem_Ch6 is
          end if;
       end if;
 
-      --  If the subprogram has a class-wide clone, build its body as a copy
-      --  of the original body, and rewrite body of original subprogram as a
-      --  wrapper that calls the clone. If N is a stub, this construction will
-      --  take place when the proper body is analyzed. No action needed if this
-      --  subprogram has been eliminated.
-
-      if Present (Spec_Id)
-        and then Present (Class_Wide_Clone (Spec_Id))
-        and then (Comes_From_Source (N) or else Was_Expression_Function (N))
-        and then Nkind (N) /= N_Subprogram_Body_Stub
-        and then not (Expander_Active and then Is_Eliminated (Spec_Id))
-      then
-         Build_Class_Wide_Clone_Body (Spec_Id, N);
-
-         --  This is the new body for the existing primitive operation
-
-         Rewrite (N, Build_Class_Wide_Clone_Call
-           (Sloc (N), New_List, Spec_Id, Parent (Spec_Id)));
-         Set_Has_Completion (Spec_Id, False);
-         Analyze (N);
-         return;
-      end if;
-
       --  Place subprogram on scope stack, and make formals visible. If there
       --  is a spec, the visible entity remains that of the spec.
 
@@ -10413,6 +10390,7 @@ package body Sem_Ch6 is
    begin
       Set_Is_Immediately_Visible (E);
       Set_Current_Entity (E);
+      pragma Assert (Prev /= E);
       Set_Homonym (E, Prev);
    end Install_Entity;