Consider associative types in utils::GenericsSearch

[tyranron]

Revealed from #473

Synopsis

utils::GenericsSearch doesn't consider associative type, leading to missing trait bounds in AsRef/AsMut expansions.

#[derive(AsRef)]
#[as_ref(forward)]
struct Forward<T: Some> {
    first: T::Assoc,
}

expands as:

#[allow(deprecated)]
#[allow(unreachable_code)]
#[automatically_derived]
impl<T: Some, __AsT: ?derive_more::core::marker::Sized> derive_more::core::convert::AsRef<__AsT> for Forward<T>
{
    #[inline]
    fn as_ref(&self) -> &__AsT { <T::Assoc as derive_more::core::convert::AsRef<__AsT>>::as_ref(&self.first) }
}

but should expand as:

#[allow(deprecated)]
#[allow(unreachable_code)]
#[automatically_derived]
impl<T: Some, __AsT: ?derive_more::core::marker::Sized> derive_more::core::convert::AsRef<__AsT> for Forward<T>
where
    T::Assoc: derive_more::core::convert::AsRef<__AsT>,
{
    #[inline]
    fn as_ref(&self) -> &__AsT { <T::Assoc as derive_more::core::convert::AsRef<__AsT>>::as_ref(&self.first) }
}

Solution

This PR fixes this situation and covers associative types usage in AsRef/AsMut tests.

Additionally

Improves utils::GenericsSearch performance by early returns (stop Visiting whenever something is found).

Also, unit tests for utils::GenericsSearch are added.

Checklist

• Documentation is updated (not required)
• Tests are added/updated
• CHANGELOG entry is added

[tyranron]

ping @JelteF