Adds a test with a vistior that can only be used as a rvalue.
Without std::forward in expr::visit this test doesn't compile.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
Add tests for new expr::visit to ensure that it is working correctly.
expr::visit had a hidden bug where trying to return a reference
actually returned a reference to freed location on the stack,
so now there are tests to ensure that everything works.
Sadly the test `expr_visit_const_ref` also passes
before the fix, but at lest expr_visit_ref doesn't compile before the fix.
It would be better to test this by taking references returned
by std::visit and expr::visit and checking that they point
to the same address in memory, but I can't do this
because I would have to access private field of expression.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
