[gcc r13-4287] ada: Spurious error on Lock_Free protected type with discriminants

[Marc Poulhi?s <dkm@gcc.gnu.org>]

https://gcc.gnu.org/g:af94026524eafbe1270e28e5142e5958a4dadf07

commit r13-4287-gaf94026524eafbe1270e28e5142e5958a4dadf07
Author: Justin Squirek <squirek@adacore.com>
Date:   Wed Nov 23 07:56:45 2022 +0000

    ada: Spurious error on Lock_Free protected type with discriminants
    
    This patch corrects an issue in the compiler whereby unprefixed discriminants
    appearing in protected subprograms were unable to be properly resolved -
    leading to spurious resolution errors.
    
    gcc/ada/
    
            * sem_ch8.adb
            (Find_Direct_Name): Remove bypass to reanalyze incorrectly
            analyzed discriminals.
            (Set_Entity_Or_Discriminal): Avoid resetting the entity field of a
            discriminant reference to be the internally generated renaming
            when we are in strict preanalysis mode.

Diff:
---
 gcc/ada/sem_ch8.adb | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/gcc/ada/sem_ch8.adb b/gcc/ada/sem_ch8.adb
index ca306663791..841076bbd01 100644
--- a/gcc/ada/sem_ch8.adb
+++ b/gcc/ada/sem_ch8.adb
@@ -4891,6 +4891,18 @@ package body Sem_Ch8 is
          then
             null;
 
+         --  Don't replace the discriminant in strict preanalysis mode since
+         --  it can lead to errors during full analysis when the discriminant
+         --  gets referenced later.
+
+         --  This can occur in situations where a protected type contains
+         --  an expression function which references a discriminant.
+
+         elsif Preanalysis_Active
+           and then Inside_Preanalysis_Without_Freezing = 0
+         then
+            null;
+
          else
             Set_Entity (N, Discriminal (E));
          end if;
@@ -6048,21 +6060,6 @@ package body Sem_Ch8 is
          if Is_Type (Entity (N)) then
             Set_Etype (N, Entity (N));
 
-         --  The exception to this general rule are constants associated with
-         --  discriminals of protected types because for each protected op
-         --  a new set of discriminals is internally created by the frontend
-         --  (see Exp_Ch9.Set_Discriminals), and the current decoration of the
-         --  entity pointer may have been set as part of a preanalysis, where
-         --  discriminals still reference the first subprogram or entry to be
-         --  expanded (see Expand_Protected_Body_Declarations).
-
-         elsif Full_Analysis
-           and then Ekind (Entity (N)) = E_Constant
-           and then Present (Discriminal_Link (Entity (N)))
-           and then Is_Protected_Type (Scope (Discriminal_Link (Entity (N))))
-         then
-            goto Find_Name;
-
          else
             declare
                Entyp : constant Entity_Id := Etype (Entity (N));
@@ -6102,8 +6099,6 @@ package body Sem_Ch8 is
          return;
       end if;
 
-      <<Find_Name>>
-
       --  Preserve relevant elaboration-related attributes of the context which
       --  are no longer available or very expensive to recompute once analysis,
       --  resolution, and expansion are over.