This allows exactly one arbitrary payload in any element, and is handled
after every other element with a more specific matcher has been parsed.
Both the #[xml(element(n = 1))] meta and its shortcut #[xml(element)]
are allowed and treated the exact same way.
The case this affects is a field like:
```
struct Foo {
#[xml(extract(fields(text(type_ = String)), namespace = .., name = ..))]
foo: ServiceType,
}
```
Before, we get this:
```
error[E0631]: type mismatch in closure arguments
--> muchopper/libmuchopper/src/xmpp/sjn_api.rs:188:10
|
188 | #[derive(AsXml)]
| ^^^^^
| |
| expected due to this
| found signature defined here
|
= note: expected closure signature `fn(&ServiceType) -> _`
found closure signature `fn(&'xso_proc_as_xml_iter_lifetime std::string::String) -> _`
note: required by a bound in `std::option::Option::<T>::map`
--> /home/jssfr/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1102:12
|
1100 | pub fn map<U, F>(self, f: F) -> Option<U>
| --- required by a bound in this associated function
1101 | where
1102 | F: FnOnce(T) -> U,
| ^^^^^^^^^^^^^^ required by this bound in `Option::<T>::map`
= note: this error originates in the derive macro `AsXml` (in Nightly builds, run with -Z macro-backtrace for more info)
```
Afterwards, this:
```
error[E0308]: mismatched types
--> muchopper/libmuchopper/src/xmpp/sjn_api.rs:207:20
|
206 | #[xml(extract(namespace = ECS, name = "service-type", fields(text(type_ = String))))]
| ------ expected due to this
207 | pub service_type: ServiceType,
| ^^^^^^^^^^^ expected `Option<&String>`, found `Option<&ServiceType>`
|
= note: expected enum `std::option::Option<&'xso_proc_as_xml_iter_lifetime std::string::String>`
found enum `std::option::Option<&ServiceType>`
```
skip-changelog, because this affects a feature which already has an
"Added" line in the changelog.
This reverts commit 4e5f0bc961.
Unfortunately, in std contexts, the `alloc` crate is not imported. That
means we cannot rely on it being accessible and it in fact breaks builds
of crates which are not `no_std`.
Fixes#155.
The old error message was pointing at the `FromXml` / `AsXml` invocation
and not on the field which actually caused the problem. The new error
message points exactly at the type of the affected field.
This declutters the main `xso` namespace. In addition, if (when) we
introduce more complex generic implementations, we might want to have
tests for these, and those can then live there, too, without making the
main `lib.rs` file gigantic (or moving the tests too far away from the
tested code).
This decreases indentation levels on the various implemenations, it
groups the implementations together physically, and (spoiler alert!)
we'll actually need the dyn Field trait object-ness (much) later on.
