Support for inner types

[carlos-verdes]

This macro fails when you have inner types as context bounds of your trait functions.

Consider you have this type:

#[trait_variant::make(Aggregate: Send)]
pub trait LocalAggregate: Default + Serialize + DeserializeOwned + Sync + Send + Stream {
    type Command: Send + Sync;

    type Error: std::error::Error + From<AggregateStoreError>;
    type Services: Send + Sync;

    fn handle(
        &self,
        command: &Self::Command,
        services: &Self::Services,
    ) -> impl Future<Output = Result<Vec<Self::Event>, Self::Error>>;
}

And you want to implement a trait where you can handle this aggregate commands like this:

#[trait_variant::make(AggregateStore: Send)]
pub trait LocalAggregateStore {

    fn apply_command_and_store_events<A: Aggregate,>(
        &self,
        stream_id: &Urn,
        stream_type: String,
        metadata: crate::Metadata,
        command: A::Command,
        expected_version: Option<i64>,
    ) -> impl Future<Output = Result<(), A::Error>>
}

This fails to compile with next error:

 --> es/src/persistence/store.rs:32:9
   |
32 |         command: A::Command,
   |         ^^^^^^^ cannot infer type
   |
   = note: cannot satisfy `<_ as Aggregate>::Command == _`

[carlos-verdes]

Tried changing the function to this:

fn apply_command_and_store_events<A: crate::Aggregate<Command = C>, C>(
        &self,
        stream_id: &Urn,
        stream_type: String,
        metadata: crate::Metadata,
        command: C,
        expected_version: Option<i64>,
    ) -> impl Future<Output = Result<(), A::Error>>;

Lead to next error:

note: required by a bound in `EventStore::apply_command_and_store_events`
  --> es/src/persistence/store.rs:27:42
   |
27 |     fn apply_command_and_store_events<A: crate::Aggregate<Command = C>, C>(
   |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `EventStore::apply_command_and_store_events`
   = note: this error originates in the attribute macro `trait_variant::make` (in Nightly builds, run with -Z macro-backtrace for more info)