3262: Fix handling of const patterns r=matklad a=flodiebold
E.g. in `match x { None => ... }`, `None` is a path pattern (resolving to the
option variant), not a binding. To determine this, we need to try to resolve the
name during lowering. This isn't too hard since we already need to resolve names
for macro expansion anyway (though maybe a bit hacky).
Fixes#1618.
Co-authored-by: Florian Diebold <florian.diebold@freiheit.com>
baf832d6d9