Move FromVariant to a separate crate
swc: - make parser respect `jsc.target`.
- cargo fix - update all crates to 2018 edition
`Map<T>` adds a method named `map` which is actually `Box<T>` -> `Box<T>` without reallocation. swc_ecma_transforms: - chain_at!(Type, passes) This macro deeply joins path at 'Type' level.