* Add a 'default' field to metadata. It contains code to generate the
default value.
* wasm update
* Make 'default' field an `Option`
* Boxed fn is not static, that won't be fine
* static fn won't do it to as it cannot get T param, will try fat trait
* Fat pointer over phantom data compatible with static instantiation
* DecodeDifferent is cool, using it for decoding.
* using once cell to do what would require copying lazy_static internals.
* Remove cache when no_std (non compatible deps)
* wasm bins update
* Fuse tooling struct and enum derive.