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[Ada] Wrong replacement of Component.Discriminant

Message ID 20201130141712.GA117900@adacore.com
State New
Headers show
Series [Ada] Wrong replacement of Component.Discriminant | expand

Commit Message

Pierre-Marie de Rodat Nov. 30, 2020, 2:17 p.m. UTC 
The procedure Replace_Discr_Ref added a few years ago is overzealous and
triggers in too many cases in the case of multiple records with
discriminants involved. It appears that this procedure is no longer
needed at this stage, so simply remove it.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* exp_ch3.adb (Replace_Discr_Ref): Removed, no longer needed.
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Patch

diff --git a/gcc/ada/exp_ch3.adb b/gcc/ada/exp_ch3.adb
--- a/gcc/ada/exp_ch3.adb
+++ b/gcc/ada/exp_ch3.adb
@@ -2008,47 +2008,6 @@  package body Exp_Ch3 is
          Lhs      : Node_Id;
          Res      : List_Id;
 
-         function Replace_Discr_Ref (N : Node_Id) return Traverse_Result;
-         --  Analysis of the aggregate has replaced discriminants by their
-         --  corresponding discriminals, but these are irrelevant when the
-         --  component has a mutable type and is initialized with an aggregate.
-         --  Instead, they must be replaced by the values supplied in the
-         --  aggregate, that will be assigned during the expansion of the
-         --  assignment.
-
-         -----------------------
-         -- Replace_Discr_Ref --
-         -----------------------
-
-         function Replace_Discr_Ref (N : Node_Id) return Traverse_Result is
-            Val : Node_Id;
-
-         begin
-            if Is_Entity_Name (N)
-              and then Present (Entity (N))
-              and then Is_Formal (Entity (N))
-              and then Present (Discriminal_Link (Entity (N)))
-            then
-               Val :=
-                 Make_Selected_Component (Default_Loc,
-                   Prefix        => New_Copy_Tree (Lhs),
-                   Selector_Name =>
-                     New_Occurrence_Of
-                       (Discriminal_Link (Entity (N)), Default_Loc));
-
-               if Present (Val) then
-                  Rewrite (N, New_Copy_Tree (Val));
-               end if;
-            end if;
-
-            return OK;
-         end Replace_Discr_Ref;
-
-         procedure Replace_Discriminant_References is
-           new Traverse_Proc (Replace_Discr_Ref);
-
-      --  Start of processing for Build_Assignment
-
       begin
          Lhs :=
            Make_Selected_Component (Default_Loc,
@@ -2056,22 +2015,6 @@  package body Exp_Ch3 is
              Selector_Name => New_Occurrence_Of (Id, Default_Loc));
          Set_Assignment_OK (Lhs);
 
-         if Nkind (Exp) = N_Aggregate
-           and then Has_Discriminants (Typ)
-           and then not Is_Constrained (Base_Type (Typ))
-         then
-            --  The aggregate may provide new values for the discriminants
-            --  of the component, and other components may depend on those
-            --  discriminants. Previous analysis of those expressions have
-            --  replaced the discriminants by the formals of the initialization
-            --  procedure for the type, but these are irrelevant in the
-            --  enclosing initialization procedure: those discriminant
-            --  references must be replaced by the values provided in the
-            --  aggregate.
-
-            Replace_Discriminant_References (Exp);
-         end if;
-
          --  Case of an access attribute applied to the current instance.
          --  Replace the reference to the type by a reference to the actual
          --  object. (Note that this handles the case of the top level of