[COMMITTED 42/54] ada: Fix ICE on static predicate when all case alternatives are False

[Marc Poulhiès]

From: Mathias Aparicio <apari...@adacore.com>

Before this patch, creating a pragma predicate with the static keyword
whose body included a case-expression where every alternative was
statically evaluated to false leads to an ICE.

When the case expression had all alternatives resolved to False,
Build_Discrete_Static_Predicate.Get_Rlist returned an Empty list and
later in the code Next was called on the Empty List.

Now return false_range in this case.

gcc/ada/ChangeLog:

        * sem_ch13.adb (Build_Discrete_Static_Predicate.Get_RList): If
        case expression alternatives are False return False_Range.

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

---
 gcc/ada/sem_ch13.adb | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gcc/ada/sem_ch13.adb b/gcc/ada/sem_ch13.adb
index 722999da459..47230c2f4d7 100644
--- a/gcc/ada/sem_ch13.adb
+++ b/gcc/ada/sem_ch13.adb
@@ -10167,6 +10167,9 @@ package body Sem_Ch13 is
                      Next (Alt);
                   end loop;
 
+                  if Is_Empty_List (Choices) then
+                     return False_Range;
+                  end if;
                   return Membership_Entries (First (Choices), Static);
                end;
 
-- 
2.53.0