[COMMITTED] Add virtual destructor to AbstractExpr

[Sam James]

From: Owen Avery <powerboat9.ga...@gmail.com>

gcc/rust/ChangeLog:

        * checks/errors/borrowck/rust-bir.h
        (class AbstractExpr): Add virtual destructor.

Signed-off-by: Owen Avery <powerboat9.ga...@gmail.com>
---
 gcc/rust/checks/errors/borrowck/rust-bir.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gcc/rust/checks/errors/borrowck/rust-bir.h 
b/gcc/rust/checks/errors/borrowck/rust-bir.h
index 4c298f147736..ed1f44686bc3 100644
--- a/gcc/rust/checks/errors/borrowck/rust-bir.h
+++ b/gcc/rust/checks/errors/borrowck/rust-bir.h
@@ -139,6 +139,8 @@ class AbstractExpr : public Visitable
 public:
   explicit AbstractExpr (ExprKind kind) : kind (kind) {}
   WARN_UNUSED_RESULT ExprKind get_kind () const { return kind; }
+
+  virtual ~AbstractExpr () {}
 };
 
 class InitializerExpr : public VisitableImpl<AbstractExpr, InitializerExpr>
-- 
2.46.2