> Special-casing the T_DEFAULT grammar would not only bloat the grammar rules > but also increase the chance that new expression grammars introduced in > future, which could conveniently interoperate with `default`, would be > unintentionally excluded by omission.
Forgot to add that I don't think the fact doing this properly requires a more complex grammar is a strong argument for doing it "the easy way" of allowing all expressions. It's a special case, and that should be reflected in the grammar.
