Matches of type unit can yield invalid C

[scolsen]

Given:

(match ()
  _ ())

Carp emits:

if(true) {                                                                                 
  void _83_temp = ;                                                                      
  void wildcard_84 = _83_temp;                                                           
  /* () */                                                                               
} 

Which is invalid C. We should filter out such emissions or dissallow matches against type ()