- Move the type parameter from `encode` and `decode` methods to
the trait.
- Remove `UseSpecialized(En|De)codable` traits.
- Remove blanket impls for references.
- Add `RefDecodable` trait to allow deserializing to arena-allocated
references safely.
- Remove ability to (de)serialize HIR.
- Create proc-macros `(Ty)?(En|De)codable` to help implement these new
traits.
Currently, every iteration of the main loop in `generic_extension`
instantiates a `Parser`, which is expensive because `Parser` is a large
type. Many of those instantiations are only used immutably, particularly
for simple-but-repetitive macros of the sort seen in `html5ever` and PR
68836.
This commit initializes a single "base" parser outside the loop, and
then uses `Cow` to avoid cloning it except for the mutating iterations.
This speeds up `html5ever` runs by up to 15%.
Matthew Jasper
Josh Stone
Mazdak Farrokhzad
Nicholas Nethercote
Vadim Petrochenkov