[gcc r13-646] [Ada] Fix invalid expanded code for entry families

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

https://gcc.gnu.org/g:ca03325fb3a5fbf9c8af853d4c7f199e1adb08e3

commit r13-646-gca03325fb3a5fbf9c8af853d4c7f199e1adb08e3
Author: Piotr Trojanek <trojanek@adacore.com>
Date:   Tue Apr 12 22:22:40 2022 +0200

    [Ada] Fix invalid expanded code for entry families
    
    Expansion of entry families created a slightly illegal AST with
    Elsif_Parts being an empty list. Cleanup uncovered by the work on
    detection of uninitialized scalars.
    
    gcc/ada/
    
            * exp_ch9.adb (Build_Find_Body_Index): Remove empty Elsif_Parts
            from the constructed IF statement.

Diff:
---
 gcc/ada/exp_ch9.adb | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/gcc/ada/exp_ch9.adb b/gcc/ada/exp_ch9.adb
index f9bdaf80c94..be791c3a338 100644
--- a/gcc/ada/exp_ch9.adb
+++ b/gcc/ada/exp_ch9.adb
@@ -2800,6 +2800,15 @@ package body Exp_Ch9 is
             begin
                Remove (Nod);
                Set_Else_Statements (Ret, Then_Statements (Nod));
+
+               --  If Elsif_Parts becomes empty then remove it entirely, as
+               --  otherwise we would violate the invariant of If_Statement
+               --  node described in Sinfo.
+
+               if Is_Empty_List (Elsif_Parts (Ret)) then
+                  pragma Assert (Elsif_Parts (Ret) /= No_List);
+                  Set_Elsif_Parts (Ret, No_List);
+               end if;
             end;
          end if;
       end if;