[gcc r13-188] [Ada] Fix package installation for private array type of private element

[gcc r13-188] [Ada] Fix package installation for private array type of private element

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:09cca56d660042991a7267b568641e16e77d0ba1

commit r13-188-g09cca56d660042991a7267b568641e16e77d0ba1
Author: Ed Schonberg <schonberg@adacore.com>
Date:   Wed Jan 12 12:04:58 2022 +0100

    [Ada] Fix package installation for private array type of private element
    
    The problem comes from the construction of Stream operations, which
    happens at the point a tagged type is frozen. Streams need to see the
    full view of types, so that for example the Read attribute for an array
    can be expanded into a loop over the Read attribute for the component
    type.  Now if during that expansion we have a private type we may need
    to retrieve the full view of the type to find its structure. And the
    corresponding tree must be compiled in the context of the package that
    defines the type, which might not be the current package.  The problem
    arises when both array and component types are private, then the
    described mechanism is invoked twice.
    
    gcc/ada/
    
            * exp_attr.adb (Compile_Stream_Body_In_Scope): Do not install
            package if array type and element type come from the same
            package, and the original array type is private.

Diff:
---
 gcc/ada/exp_attr.adb | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/gcc/ada/exp_attr.adb b/gcc/ada/exp_attr.adb
index 5374dd4d7e9..ab14a498117 100644
--- a/gcc/ada/exp_attr.adb
+++ b/gcc/ada/exp_attr.adb
@@ -888,6 +888,11 @@ package body Exp_Attr is
          --  special stream-processing operations for that type (for example
          --  Unbounded_String and its wide varieties).
 
+         --  We don't install the package either if array type and element
+         --  type come from the same package, and the original array type is
+         --  private, because in this case the underlying type Arr is
+         --  itself a full view, which carries the full view of the component.
+
          Scop := Scope (C_Type);
 
          if Is_Private_Type (C_Type)
@@ -896,7 +901,15 @@ package body Exp_Attr is
            and then Ekind (Scop) = E_Package
            and then No (Get_Stream_Convert_Pragma (C_Type))
          then
-            Install := True;
+            if Scope (Arr) = Scope (C_Type)
+              and then Is_Private_Type (Etype (Prefix (N)))
+              and then Full_View (Etype (Prefix (N))) = Arr
+            then
+               null;
+
+            else
+               Install := True;
+            end if;
          end if;
       end if;