Partially parse grammar

[cristiano-belloni]

Hi, I have a grammar that works well but I noticed that, if a match doesn't succeed, there is no way to get the AST. I see that in the editor it is possible to see the "partial" AST even if the parsing failed; for example, with the default grammar, if I type 1 * 2 *, which fails, I still get the viz to show 1 * 2. Do you do that just parsing whatever is before the error or is there a way to get a "partial AST of a grammar until it's not possible to parse anymore?