derive-syn-parse

Bumps syn to v2.

Other changes:

• Fix expr parsing for #[call(...)]
• Add "full" feature to enable syn's "full" feature (allows expr parsing, notably closures)

Thanks to @racharron for the help!

Adds #[prefix] and #[postfix] field attributes - and improves the crate documentation :)

Adds conditional parsing to struct fields - both through the existing #[peek] and #[peek_with] attributes, as well as the new #[parse_if] attribute. A new section in the README gives a brief example.

To briefly elaborate on the motivation here:

A pattern that tends to come up in complex Parse implementations is having optional fields. Most of these conditions boil down to either (1) peeking, or (2) some expression based on what's already been parsed. I've already found that I wanted to allow this behavior in my personal use, so it's now a feature!

Adds enum parsing with peeking (there's a new section in the README 😄), and general tidy-up. Notably changing the generated code to use ::syn everywhere instead of syn; the former is always guaranteed to point to the crate.

After a couple of false starts, this crate is being released into the wild. This is the first "official" version. link to the reddit post