The parser defines the grammar. This is quite common in mainstream languages -- iirc, only after some years did python get a formal description of a grammar.

> The parser defines the grammar.

But how can you have assurance which grammar it defines, or that it even defines a well-defined grammar?

I’m well aware that some languages don’t bother defining a proper grammar, or define it without having a mechanism to ensure their implementation matches it, but lacking that assurance is exactly the drawback of not using a parser generator.

i was puzzled about that too and got even more puzzled when i looked at the languages i could find that he's implemented