Ben Millwood wrote:
So essentially, all you are asking for is an official implementation of haskell parsing, so that you input a program and it spits out either "valid" or "not valid", according to the parts of the spec that it audits.
Yes, that is the most essential requirement. It is a desirable feature for it to work as a parser, too. It can then be used as the basis for further verification tools, and for parsing with guarantees about standards compliance. And haskell-exts does work as a parser, though it perhaps not as polished as some other parsers. If we can get a parser based on haskell-src-exts instead, that would be great. But it's more work. haskell-exts is basically ready today.
...compliance to a reference implementation... tends to be more painful as a process. If there are bugs in the reference implementation, other implementations then have to decide whether to "implement" them or do what they think is best. If there are disagreements between the reference implementation and language spec, or ambiguities in language spec, the spec should certainly be fixed! ...So I'm not convinced that converting part of the language description into a machine-readable form is necessarily for the best.
I am not suggesting converting part of the spec into code and dispensing with that part of the document. I am suggesting that both the human-readable document and the reference parser should be officially part of the spec. If there is inconsistency between them, that is a bug in the spec which needs to be fixed like any other.
...fixity resolution is one of the trickiest parts of Haskell parsing, imo. It seems like an awful cop-out to put the really difficult cases - like parsing \x -> x == x == 0 - out of the scope of your verification tool.
Yes, it should be in scope if possible. If the fixity handling of haskell-src-exts is deemed sufficient and we move to that now or in the future, we'll have it.
...it seems a bit odd to have a complete parsing library that nevertheless doesn't provide AST inspection and manipulation, which is what I guess most people use a haskell parser in Haskell for.
haskell-src does provide that. It works and it is usable. Again, if we can be based on haskell-src-exts now or in the future, all the better. Regards, Yitz