The 'FromFrom' derive now allows type generics in all positions using
the same automatic discovery technique as with 'Responder'. (In fact,
the technique was created for this derive.) Furthermore, 'FromForm' can
now be derived for unit structs.
Also adds a new 'try_with' form field validator.
Resolves#1695.
This commit presents and applies a new technique for bounding type
generics in derives. In short, for a generic `T` used in a field type of
`Field<T>`, where an eventual bound of `Responder` required, the derive
generates a bound of `Field<T>: Responder`. This removes the need for
any manually provided bounds while simultaneously allowing more
structures to typecheck. For example, generics in header components are
now fully supported.
The 'Json' type now implements:
* Clone
* PartialEq
* Eq
* PartialOrd
* Ord
* Hash
* UriDisplay<Query>
Method calls that resolve to a method in the set of traits above
previously resolved to the `Deref` target. For example, `foo.clone()`,
where `foo: Json<T>`, previously resolved to `<T as Clone>::clone()` but
now resolves to `<Json<T> as Clone>::clone()`.
'Missing' allows constructing a 'FileServer' even if the supplied path
does not exist. 'IndexFile' allows serving a single file as the index of
the mount path.
The syntax 'TypedStream![T + '_]' expands to:
impl TypedStream<Item = T> + '_
This allows seamlessly borrowing in typed streams.
Also adds 'Event::empty()', for convenience.
The improvements are:
* Point directly and immediately to the 'Responder' derive.
* Provide more discussion on lifetimes.
* Format documentation for easier scanning.
Previously, recursion into rewriting 'self' in field validations would
cease after the first function call. This meant that internal uses of
'self' were not properly rewritten. This commit ameliorates the
situation.
Previously, 'serde_json::Value' was used to store the serialized
template context. This value does not represent all of serde's data
model. This means we may fail to serialize a valid Rust value into it,
for instance, 128-bit integers. This is reduced with Figment's 'Value',
which supports the majority if not all of the serde data model.
At present, all supported templating engines use 'serde_json::Value', so
in practice, this commit has no effect but to reduce local dependencies
and provide better error messages for bad contexts.
