[gcc r13-1664] [Ada] Fix incorrect handling of Ghost aspect

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:8e3030ea9ae79880850c821887c9aa06a76ac21b

commit r13-1664-g8e3030ea9ae79880850c821887c9aa06a76ac21b
Author: Yannick Moy <moy@adacore.com>
Date:   Tue Jul 5 12:51:25 2022 +0200

    [Ada] Fix incorrect handling of Ghost aspect
    
    When a formal generic type is marked as Ghost, the instantiation of that
    generic will contain a generic subtype for the actual with the Ghost
    pragma. Recognize this case.
    
    gcc/ada/
    
            * sem_prag.adb (Analyze_Pragma): Recognize a generated subtype
            with Ghost pragma for generic instantiations.

Diff:
---
 gcc/ada/sem_prag.adb | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
index 982fdf811c6..df3d348b3a7 100644
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -16999,6 +16999,16 @@ package body Sem_Prag is
                   then
                      Id := Defining_Entity (Stmt);
                      exit;
+
+                  --  When pragma Ghost applies to a generic formal type, the
+                  --  type declaration in the instantiation is a generated
+                  --  subtype declaration.
+
+                  elsif Nkind (Stmt) = N_Subtype_Declaration
+                    and then Present (Generic_Parent_Type (Stmt))
+                  then
+                     Id := Defining_Entity (Stmt);
+                     exit;
                   end if;
 
                --  The pragma applies to a legal construct, stop the traversal