code: def op_match_funcdef_handle(self, original, loc, tokens):
          
          if len(tokens) == 3:
              func, args = get_infix_items(tokens)
              cond = None
          elif len(tokens) == 4:
              func, args = get_infix_items(tokens[:-1])
              cond = tokens[-1]
          else:
              raise CoconutInternalException("invalid infix match function definition tokens", tokens)
          name_tokens = [func, args]
          if cond is not None:
              name_tokens.append(cond)
          return self.name_match_funcdef_handle(original, loc, name_tokens)
docs: Process infix match defs. Result must be passed to insert_docstring_handle.