Defining an edge in (a -> b) format using anything other than identifiers doesn't work

[ValikVityaz]

a -> b;;
@link_a = a;;
@link_b = b;;
@edge_alias = (@link_b -> @link_a);;

Getting a parser error when trying to build the above scs code:
Parse error at line 4,15: mismatched input '@link_b' expecting {'...', 'sc_node', 'sc_link', 'sc_edge_dcommon', 'sc_edge_ucommon', 'sc_edge_main', 'sc_edge_access', 'sc_arc_common', 'sc_edge', 'sc_arc_main', 'sc_arc_access', ID_SYSTEM}

Also fails:

@test = (a -> [asdf]);;