[COMMITTED 5/5] ada: Robustify error recovery of structural instantiation in generic formal part

[Marc Poulhiès]

From: Eric Botcazou <ebotca...@adacore.com>

The previous attempt didn't address the root cause of the cascading errors,
so this rewinds it and starts from scratch.

gcc/ada/ChangeLog:

        * sem_ch3.adb (Analyze_Private_Extension_Declaration): Revert latest
        change.
        (Find_Type_Of_Subtype_Indic): Return Any_Type if Find_Type fails to
        resolve the type.
        * sem_ch12.adb (Analyze_Formal_Derived_Type): Restore more specific
        error recovery path.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/sem_ch12.adb |  5 +++--
 gcc/ada/sem_ch3.adb  | 10 +++++-----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/gcc/ada/sem_ch12.adb b/gcc/ada/sem_ch12.adb
index 914df9d8d48..08ee37547fb 100644
--- a/gcc/ada/sem_ch12.adb
+++ b/gcc/ada/sem_ch12.adb
@@ -3220,8 +3220,9 @@ package body Sem_Ch12 is
          end if;
       end if;
 
-      if Serious_Errors_Detected > 0 then
-         --  avoid passing bad argument to Entity
+      if not Is_Entity_Name (Subtype_Mark (Def)) then
+         pragma Assert (Serious_Errors_Detected > 0);
+         --  Avoid passing bad argument to Entity
          return;
       end if;
 
diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 180bd30c0df..1ada2512377 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -5578,11 +5578,6 @@ package body Sem_Ch3 is
       end if;
 
       Parent_Type := Find_Type_Of_Subtype_Indic (Indic);
-      if No (Parent_Type) then
-         pragma Assert (Serious_Errors_Detected > 0);
-         goto Leave;
-      end if;
-
       Parent_Base := Base_Type (Parent_Type);
 
       if Parent_Type = Any_Type or else Etype (Parent_Type) = Any_Type then
@@ -19305,6 +19300,11 @@ package body Sem_Ch3 is
 
       else
          Find_Type (S);
+         if not Is_Entity_Name (S) then
+            pragma Assert (Serious_Errors_Detected > 0);
+            --  Avoid passing bad argument to Entity
+            return Any_Type;
+         end if;
          Typ := Entity (S);
       end if;
 
-- 
2.53.0