Bison grammar is outdated

[pekabon]

It looks like grammar (https://github.com/rust-lang/rust/tree/master/src/grammar) is outdated, for example '?' shortcut for try! is not supported.

[steveklabnik]

Well, one question is, should the grammar show nightly-only things. If so, it would not include ?. That said, it's clearly not complete, if you look at all the A-grammar tags.

@nikomatsakis has been working on a larlpop grammar that would hopefully make this stuff easier...

[alexcrichton]

cc #15880, a bot which is intended to run these tests

[Mark-Simulacrum]

I don't think we have a bison grammar in-tree anymore... @nikomatsakis @steveklabnik @alexcrichton Do you know of the current state of the in-tree grammar? Do we want to show nightly-only things in the grammar?

[alexcrichton]

Oh I have no idea what's up with the current in-tree grammar, I would expect it to be quite out of date at this point.

[steveklabnik]

Yeah, it's basically abandonware. Niko had some efforts to have a real one, but I assume anything we do have is horribly bit-rotted.

[Mark-Simulacrum]

Do we want to try and get some movement from the community on implementing a reference grammar? Is it something we're interested in maintaining? If not, we should probably go ahead and close out issues relevant to the reference grammar; if yes, arguably closing the issues in favor of a thread on internals would still be a good idea.

[steveklabnik]

if yes, arguably closing the issues in favor of a thread on internals would still be a good idea.

I would go this route, but let's hear what @nikomatsakis has to say

[chordowl]

Traige: There is ongoing work (as of about two weeks ago) on creating an up-to-date grammar in the reference (rust-lang/reference#84); generally, this issue seems to under #30942 when it comes to a machine-readable grammar, and the reference issue when it comes to just having some up-to-date grammar.

[steveklabnik]

Triage: there's a new grammar wg, and i don't even think the bison grammar still exists. closing as outdated.

[tromey]

I still see src/grammar/parser-lalr.y in my tree - perhaps it should be removed?

[steveklabnik]

After posting that comment, I checked it out again and saw that it was still there, which led to #55545