Note that the token constant values have changed because I built with Bison 3.0.2 instead of 2.7

In D10337#164167, @epriestley wrote:

The use of yyerror() explicitly is unusual, and does not seem to come from zend_language_parser.y. I'd rather see this prevented by the grammar itself. It looks like zend_language_parser.y accomplished this purely with grammar rules, at least as of 5.5.14 (the copy of the PHP source I have handy locally).

This is not true - it's handled in zend_compile.c. The grammar allows omitting catch/finally.

I can implement it in the grammar without too much problems. I really need this to work now.

For lists, I generally see the "n_X_LIST with no members" approach.

parameter_list:
  non_empty_parameter_list
| %empty {
    $$ = NNEW(n_DECLARATION_PARAMETER_LIST);
  }
;

inner_statement_list:
  inner_statement_list inner_statement {
    $$ = $1->appendChild($2);
  }
| %empty {
    $$ = NNEW(n_STATEMENT_LIST);
  }
;

… and more alike.

Works for me.

(The n_CATCH_LIST was previously always-nonempty, right? But those %empty examples are compelling to me.)

In D10337#178632, @epriestley wrote:

(The n_CATCH_LIST was previously always-nonempty, right? … )

Hmm yes, that is true. It's hard to think of a real-world scenario in which it should matter though.