Use is_propset in emitfunc

Author: p-sawicki

mypyc/codegen/emitfunc.py

@@ -484,7 +484,7 @@ def visit_set_attr(self, op: SetAttr) -> None:
         rtype = op.class_type
         cl = rtype.class_ir
         attr_rtype, decl_cl = cl.attr_details(op.attr)
-        if cl.get_method(op.attr):
+        if op.is_propset:
             # Again, use vtable access for properties...
             assert not op.is_init and op.error_kind == ERR_FALSE, "%s %d %d %s" % (
                 op.attr,